Java: Proposal for adding hooks (#4730)

### Motivation and Context

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  1. Why is this change required?
  2. What problem does it solve?
  3. What scenario does it contribute to?
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### Description

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### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

java/aiservices/openai/pom.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
 
     <parent>
@@ -33,6 +34,13 @@
             <artifactId>jackson-core</artifactId>
             <scope>compile</scope>
         </dependency>
+
+        <!-- Required for Android -->
+        <dependency>
+            <groupId>javax.xml.stream</groupId>
+            <artifactId>stax-api</artifactId>
+            <version>1.0-2</version>
+        </dependency>
     </dependencies>
 
 </project>

java/aiservices/openai/src/main/java/com/microsoft/semantickernel/aiservices/openai/chatcompletion/OpenAIChatCompletion.java

@@ -26,6 +26,9 @@ import com.microsoft.semantickernel.chatcompletion.ChatHistory;
 import com.microsoft.semantickernel.chatcompletion.ChatMessageContent;
 import com.microsoft.semantickernel.chatcompletion.StreamingChatMessageContent;
 import com.microsoft.semantickernel.exceptions.AIException;
+import com.microsoft.semantickernel.hooks.KernelHooks;
+import com.microsoft.semantickernel.hooks.PreChatCompletionEvent;
+import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.FunctionResultMetadata;
 import com.microsoft.semantickernel.orchestration.KernelFunction;
 import com.microsoft.semantickernel.orchestration.PromptExecutionSettings;
@@ -33,7 +36,6 @@ import com.microsoft.semantickernel.orchestration.ToolCallBehavior;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariable;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariableType;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariableTypes;
-import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
@@ -69,7 +71,7 @@ public class OpenAIChatCompletion implements ChatCompletionService {
 
     @Override
     public Map<String, ContextVariable<?>> getAttributes() {
-        return attributes;
+        return Collections.unmodifiableMap(attributes);
     }
 
     @Override
@@ -78,56 +80,101 @@ public class OpenAIChatCompletion implements ChatCompletionService {
     }
 
     @Override
-    public Mono<List<ChatMessageContent>> getChatMessageContentsAsync(ChatHistory chatHistory,
-        @Nullable PromptExecutionSettings promptExecutionSettings, @Nullable Kernel kernel) {
+    public Mono<List<ChatMessageContent>> getChatMessageContentsAsync(
+        ChatHistory chatHistory,
+        PromptExecutionSettings promptExecutionSettings,
+        Kernel kernel,
+        KernelHooks kernelHooks) {
 
         List<ChatRequestMessage> chatRequestMessages = getChatRequestMessages(chatHistory);
         List<FunctionDefinition> functions = Collections.emptyList();
-        return internalChatMessageContentsAsync(chatRequestMessages, functions,
-            promptExecutionSettings);
 
+        if (kernelHooks == null) {
+            kernelHooks = new KernelHooks();
+        }
+
+        return internalChatMessageContentsAsync(
+            chatRequestMessages,
+            functions,
+            promptExecutionSettings,
+            kernelHooks);
+    }
+
+    @Override
+    public Mono<List<ChatMessageContent>> getChatMessageContentsAsync(
+        ChatHistory chatHistory,
+        @Nullable PromptExecutionSettings promptExecutionSettings,
+        @Nullable Kernel kernel) {
+        return getChatMessageContentsAsync(chatHistory, promptExecutionSettings, kernel, null);
+    }
+
+
+    @Override
+    public Mono<List<ChatMessageContent>> getChatMessageContentsAsync(
+        String prompt,
+        PromptExecutionSettings promptExecutionSettings,
+        Kernel kernel,
+        @Nullable
+        KernelHooks kernelHooks) {
+        ParsedPrompt parsedPrompt = XMLPromptParser.parse(prompt);
+
+        if (kernelHooks == null) {
+            kernelHooks = new KernelHooks();
+        }
+
+        return internalChatMessageContentsAsync(
+            parsedPrompt.getChatRequestMessages(),
+            parsedPrompt.getFunctions(),
+            promptExecutionSettings,
+            kernelHooks);
     }
 
     @Override
     public Mono<List<ChatMessageContent>> getChatMessageContentsAsync(String prompt,
         PromptExecutionSettings promptExecutionSettings, Kernel kernel) {
-        ParsedPrompt parsedPrompt = XMLPromptParser.parse(prompt);
-        return internalChatMessageContentsAsync(
-            parsedPrompt.getChatRequestMessages(),
-            parsedPrompt.getFunctions(),
-            promptExecutionSettings);
+        return getChatMessageContentsAsync(prompt, promptExecutionSettings, kernel, null);
     }
 
+
     private Mono<List<ChatMessageContent>> internalChatMessageContentsAsync(
         List<ChatRequestMessage> chatRequestMessages,
         List<FunctionDefinition> functions,
-        PromptExecutionSettings promptExecutionSettings) {
+        PromptExecutionSettings promptExecutionSettings,
+        KernelHooks kernelHooks) {
+
         ChatCompletionsOptions options = getCompletionsOptions(this, chatRequestMessages, functions,
             promptExecutionSettings);
         Mono<List<ChatMessageContent>> results =
-            internalChatMessageContentsAsync(options);
+            internalChatMessageContentsAsync(kernelHooks, options);
 
-        return results.flatMap(list -> {
-            boolean makeSecondCall = false;
-            for (ChatMessageContent messageContent : list) {
-                if (messageContent.getAuthorRole() == AuthorRole.TOOL) {
-                    makeSecondCall = true;
-                    String content = messageContent.getContent();
-                    String id = messageContent.getModelId();
-                    ChatRequestToolMessage toolMessage = new ChatRequestToolMessage(content, id);
-                    chatRequestMessages.add(toolMessage);
+        return results
+            .flatMap(list -> {
+                boolean makeSecondCall = false;
+                for (ChatMessageContent messageContent : list) {
+                    if (messageContent.getAuthorRole() == AuthorRole.TOOL) {
+                        makeSecondCall = true;
+                        String content = messageContent.getContent();
+                        String id = messageContent.getModelId();
+                        ChatRequestToolMessage toolMessage = new ChatRequestToolMessage(content,
+                            id);
+                        chatRequestMessages.add(toolMessage);
+                    }
                 }
-            }
-            if (makeSecondCall) {
-                return internalChatMessageContentsAsync(options);
-            }
-            return Mono.just(list);
-        });
+                if (makeSecondCall) {
+                    return internalChatMessageContentsAsync(kernelHooks, options);
+                }
+                return Mono.just(list);
+            });
     }
 
     private Mono<List<ChatMessageContent>> internalChatMessageContentsAsync(
+        KernelHooks kernelHooks,
         ChatCompletionsOptions options) {
 
+        options = kernelHooks
+            .executeHooks(new PreChatCompletionEvent(options))
+            .getOptions();
+
         return client
             .getChatCompletions(getModelId(), options)
             .filter(choices -> choices.getChoices() != null && !choices.getChoices().isEmpty())

java/aiservices/openai/src/main/java/com/microsoft/semantickernel/aiservices/openai/chatcompletion/XMLPromptParser.java

@@ -11,6 +11,7 @@ import com.microsoft.semantickernel.exceptions.SKException;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -61,7 +62,7 @@ class XMLPromptParser {
         // If one handler does not recognize the element, it should pass it to the next handler.
         // In this way, we can avoid parsing the whole prompt twice and easily extend the parsing logic.
         List<ChatRequestMessage> messages = new ArrayList<>();
-        try (InputStream is = new ByteArrayInputStream(prompt.getBytes())) {
+        try (InputStream is = new ByteArrayInputStream(prompt.getBytes(StandardCharsets.UTF_8))) {
             XMLInputFactory factory = XMLInputFactory.newFactory();
             XMLEventReader reader = factory.createXMLEventReader(is);
             while (reader.hasNext()) {
@@ -87,7 +88,7 @@ class XMLPromptParser {
         //      <parameter name=\"%s\" description=\"%s\" defaultValue=\"%s\" isRequired=\"%s\" type=\"%s\"/>...
         // </function>
         List<FunctionDefinition> functionDefinitions = new ArrayList<>();
-        try (InputStream is = new ByteArrayInputStream(prompt.getBytes())) {
+        try (InputStream is = new ByteArrayInputStream(prompt.getBytes(StandardCharsets.UTF_8))) {
             XMLInputFactory factory = XMLInputFactory.newFactory();
             XMLEventReader reader = factory.createXMLEventReader(is);
             FunctionDefinition functionDefinition = null;

java/aiservices/openai/src/main/java/com/microsoft/semantickernel/aiservices/openai/textcompletion/OpenAITextGenerationService.java

@@ -51,7 +51,7 @@ public class OpenAITextGenerationService implements TextGenerationService {
 
     @Override
     public Map<String, ContextVariable<?>> getAttributes() {
-        return attributes;
+        return Collections.unmodifiableMap(attributes);
     }
 
     @Override

java/connectors/semantickernel-connectors-web-bing/src/main/java/com/microsoft/semantickernel/connectors/web/bing/BingConnector.java

@@ -21,7 +21,7 @@ import com.microsoft.semantickernel.exceptions.SKException;
 
 import reactor.core.publisher.Mono;
 
-public class BingConnector implements WebSearchEngineConnector {    
+public class BingConnector implements WebSearchEngineConnector {
 
     private static String BING_SEARCH_URL;
     static { 
@@ -91,7 +91,7 @@ public class BingConnector implements WebSearchEngineConnector {
         @Override
         public String getSnippet() {
             return snippet;
-        }   
+        }
     }
 
     private final String apiKey; // TODO: secure this
@@ -107,7 +107,7 @@ public class BingConnector implements WebSearchEngineConnector {
     }
 
     @Override
-    public Mono<List<WebPage>> searchAsync(String query, int count, int offset) {   
+    public Mono<List<WebPage>> searchAsync(String query, int count, int offset) {
 
         if (count <= 0 || 50 <= count) throw new IllegalArgumentException("count must be between 1 and 50");
         if (offset < 0) throw new IllegalArgumentException("offset must be greater than or equal to 0");

java/plugins/semantickernel-plugin-core/src/main/java/com/microsoft/semantickernel/util/LocaleParser.java

@@ -1,9 +1,8 @@
 // Copyright (c) Microsoft. All rights reserved.
 package com.microsoft.semantickernel.util;
 
-import java.util.Locale;
-
 import com.microsoft.semantickernel.plugin.annotations.KernelFunctionParameter;
+import java.util.Locale;
 
 
 /**
@@ -14,7 +13,8 @@ import com.microsoft.semantickernel.plugin.annotations.KernelFunctionParameter;
  */
 public final class LocaleParser {
 
-    private LocaleParser() {}
+    private LocaleParser() {
+    }
 
     /**
      * Parses the locale. If the input is "en-US", it will return a Locale based on the language
@@ -26,12 +26,13 @@ public final class LocaleParser {
      * @param locale the locale in String text.
      * @return
      */
+    @SuppressWarnings("StringSplitter")
     public static final Locale parseLocale(String locale) {
         Locale parsedLocale = null;
 
         if (locale == null
-                || "".equals(locale.trim())
-                || KernelFunctionParameter.NO_DEFAULT_VALUE.equals(locale)) {
+            || "".equals(locale.trim())
+            || KernelFunctionParameter.NO_DEFAULT_VALUE.equals(locale)) {
             return Locale.getDefault();
         } else if (locale.indexOf("-") > -1) {
             parsedLocale = Locale.forLanguageTag(locale);

java/pom.xml

@@ -15,7 +15,7 @@
     <properties>
         <azure-ai-openai.version>1.0.0-beta.6</azure-ai-openai.version>
         <checkstyle.version>10.12.2</checkstyle.version>
-        <com.uber.nullaway.version>0.10.10</com.uber.nullaway.version>
+        <com.uber.nullaway.version>0.10.21</com.uber.nullaway.version>
         <google.errorprone.core.version>2.19.1</google.errorprone.core.version>
         <google.java.format.version>1.17.0</google.java.format.version>
         <jreleaser.plugin.version>1.6.0</jreleaser.plugin.version>
@@ -60,7 +60,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.github.repository>microsoft/semantic-kernel</project.github.repository>
         <repository.url>[email protected]:${project.github.repository}.git</repository.url>
-        <spotbugs.version>4.7.3</spotbugs.version>
+        <spotbugs.version>4.8.3</spotbugs.version>
     </properties>
 
     <modules>
@@ -155,7 +155,13 @@
                 <groupId>com.microsoft.semantic-kernel</groupId>
                 <artifactId>semantickernel-connectors-web-bing</artifactId>
                 <version>${project.version}</version>
-            </dependency>            
+            </dependency>
+
+            <dependency>
+                <groupId>com.github.spotbugs</groupId>
+                <artifactId>spotbugs-annotations</artifactId>
+                <version>${spotbugs.version}</version>
+            </dependency>
         </dependencies>
     </dependencyManagement>
 
@@ -685,6 +691,7 @@
                             </execution>
                         </executions>
                         <configuration>
+                            <!--
                             <java>
                                 <googleJavaFormat>
                                     <version>${google.java.format.version}</version>
@@ -696,6 +703,7 @@
                                 </licenseHeader>
                                 <toggleOffOn />
                             </java>
+                            -->
                         </configuration>
                     </plugin>
                     <plugin>

java/samples/pom.xml

@@ -87,40 +87,26 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>animal-sniffer-maven-plugin</artifactId>
+                <version>1.23</version>
+                <executions>
+                    <execution>
+                        <id>android</id>
+                        <phase>test</phase>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <skip>true</skip>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 
-    <!-- <dependencies>
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-api</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-connectors-ai-openai</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.logging.log4j</groupId>
-            <artifactId>log4j-api</artifactId>
-            <version>${log4j2.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.logging.log4j</groupId>
-            <artifactId>log4j-core</artifactId>
-            <version>${log4j2.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.logging.log4j</groupId>
-            <artifactId>log4j-slf4j2-impl</artifactId>
-            <version>${log4j2.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-planners</artifactId>
-            <scope>compile</scope>
-        </dependency>
-    </dependencies> -->
-
     <profiles>
         <profile>
             <id>bug-check</id>
@@ -140,28 +126,16 @@
                             <target>${maven.compiler.release}</target>
                             <encoding>${project.build.sourceEncoding}</encoding>
                             <showWarnings>true</showWarnings>
-                            <compilerArgs>
-                                <arg>-XDcompilePolicy=simple</arg>
+                        </configuration>
+                    </plugin>
 
-                                <!-- Remove exclusions when more project is stable -->
-                                <arg>-Xplugin:ErrorProne
-                                    -XepOpt:NullAway:AnnotatedPackages=com.microsoft.semantickernel
-                                    -Xep:AlmostJavadoc:OFF -Xep:MissingSummary:OFF
-                                    -Xep:UnusedVariable:OFF -Xep:EmptyBlockTag:OFF
-                                </arg>
-                            </compilerArgs>
-                            <annotationProcessorPaths>
-                                <path>
-                                    <groupId>com.google.errorprone</groupId>
-                                    <artifactId>error_prone_core</artifactId>
-                                    <version>${google.errorprone.core.version}</version>
-                                </path>
-                                <path>
-                                    <groupId>com.uber.nullaway</groupId>
-                                    <artifactId>nullaway</artifactId>
-                                    <version>${com.uber.nullaway.version}</version>
-                                </path>
-                            </annotationProcessorPaths>
+                    <!-- Ignore linting on samples -->
+                    <plugin>
+                        <groupId>com.github.spotbugs</groupId>
+                        <artifactId>spotbugs-maven-plugin</artifactId>
+                        <version>${maven.spotbugs-plugin.version}</version>
+                        <configuration>
+                            <skip>true</skip>
                         </configuration>
                     </plugin>
                 </plugins>

java/samples/sample-code/pom.xml

@@ -39,17 +39,6 @@
             <groupId>com.microsoft.semantic-kernel</groupId>
             <artifactId>semantickernel-connectors-web-bing</artifactId>
         </dependency>
-        <!--
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-connectors-ai-openai</artifactId>
-            <version>${project.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-connectors-memory-azurecognitivesearch</artifactId>
-        </dependency>
-        -->
 
         <dependency>
             <groupId>org.apache.logging.log4j</groupId>
@@ -66,18 +55,6 @@
             <artifactId>log4j-slf4j2-impl</artifactId>
             <version>2.20.0</version>
         </dependency>
-        <!--
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-planners</artifactId>
-            <scope>compile</scope>
-        </dependency>
-        <dependency>
-            <groupId>com.microsoft.semantic-kernel</groupId>
-            <artifactId>semantickernel-gpt3-tokenizer</artifactId>
-            <scope>compile</scope>
-        </dependency>
-        -->
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>

java/samples/sample-code/src/main/java/com/microsoft/semantickernel/samples/syntaxexamples/Example17_ChatGPT.java

@@ -19,6 +19,7 @@ public class Example17_ChatGPT {
         .getOrDefault("MODEL_ID", "gpt-35-turbo");
 
     public static void main(String[] args) {
+
         System.out.println("======== Open AI - ChatGPT ========");
 
         OpenAIAsyncClient client;
@@ -67,6 +68,7 @@ public class Example17_ChatGPT {
     }
 
     private static void GPTReply(ChatCompletionService chatGPT, ChatHistory chatHistory) {
+
         var reply = chatGPT.getChatMessageContentsAsync(chatHistory, null, null)
             .block();
 

java/samples/sample-code/src/main/java/com/microsoft/semantickernel/samples/syntaxexamples/Example30_ChatWithPrompts.java

@@ -5,6 +5,7 @@ import com.azure.ai.openai.OpenAIClientBuilder;
 import com.azure.core.credential.AzureKeyCredential;
 import com.azure.core.credential.KeyCredential;
 import com.microsoft.semantickernel.Kernel;
+import com.microsoft.semantickernel.ServiceNotFoundException;
 import com.microsoft.semantickernel.chatcompletion.ChatCompletionService;
 import com.microsoft.semantickernel.chatcompletion.ChatHistory;
 import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
@@ -30,7 +31,7 @@ public class Example30_ChatWithPrompts {
     private static final String MODEL_ID = System.getenv()
         .getOrDefault("MODEL_ID", "gpt-35-turbo");
 
-    public static void main(String[] args) throws FileNotFoundException {
+    public static void main(String[] args) throws FileNotFoundException, ServiceNotFoundException {
         OpenAIAsyncClient client;
 
         if (AZURE_CLIENT_KEY != null) {

java/samples/sample-code/src/main/java/com/microsoft/semantickernel/samples/syntaxexamples/Example42_KernelBuilder.java

@@ -67,7 +67,8 @@ public class Example42_KernelBuilder {
         // using the public constructor that's available for anyone to use directly if desired.
         Kernel kernel = new Kernel(
             new OrderedAIServiceSelector(),
-            new KernelPluginCollection()
+            new KernelPluginCollection(),
+            null
         );
     }
 }

java/samples/sample-code/src/main/java/com/microsoft/semantickernel/samples/syntaxexamples/Example57_KernelHooks.java

@@ -0,0 +1,417 @@
+package com.microsoft.semantickernel.samples.syntaxexamples;
+
+import com.azure.ai.openai.OpenAIAsyncClient;
+import com.azure.ai.openai.OpenAIClientBuilder;
+import com.azure.ai.openai.models.ChatCompletionsOptions;
+import com.azure.ai.openai.models.ChatRequestMessage;
+import com.azure.ai.openai.models.ChatRequestSystemMessage;
+import com.azure.core.credential.AzureKeyCredential;
+import com.azure.core.credential.KeyCredential;
+import com.microsoft.semantickernel.Kernel;
+import com.microsoft.semantickernel.Kernel.Builder;
+import com.microsoft.semantickernel.aiservices.openai.chatcompletion.OpenAIChatCompletion;
+import com.microsoft.semantickernel.chatcompletion.ChatCompletionService;
+import com.microsoft.semantickernel.hooks.FunctionInvokedEvent;
+import com.microsoft.semantickernel.hooks.KernelHooks;
+import com.microsoft.semantickernel.hooks.KernelHook.FunctionInvokedHook;
+import com.microsoft.semantickernel.hooks.KernelHook.FunctionInvokingHook;
+import com.microsoft.semantickernel.hooks.KernelHook.PreChatCompletionHook;
+import com.microsoft.semantickernel.hooks.KernelHook.PromptRenderedHook;
+import com.microsoft.semantickernel.hooks.KernelHook.PromptRenderingHook;
+import com.microsoft.semantickernel.hooks.PreChatCompletionEvent;
+import com.microsoft.semantickernel.hooks.PromptRenderedEvent;
+import com.microsoft.semantickernel.orchestration.FunctionResult;
+import com.microsoft.semantickernel.orchestration.PromptExecutionSettings;
+import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariable;
+import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
+import com.microsoft.semantickernel.semanticfunctions.KernelFunctionFromPrompt;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Example57_KernelHooks {
+
+    private static final String CLIENT_KEY = System.getenv("CLIENT_KEY");
+    private static final String AZURE_CLIENT_KEY = System.getenv("AZURE_CLIENT_KEY");
+
+    // Only required if AZURE_CLIENT_KEY is set
+    private static final String CLIENT_ENDPOINT = System.getenv("CLIENT_ENDPOINT");
+    private static final String MODEL_ID = System.getenv()
+        .getOrDefault("MODEL_ID", "gpt-35-turbo");
+
+    public static void main(String[] args) {
+
+        OpenAIAsyncClient client;
+
+        if (AZURE_CLIENT_KEY != null) {
+            client = new OpenAIClientBuilder()
+                .credential(new AzureKeyCredential(AZURE_CLIENT_KEY))
+                .endpoint(CLIENT_ENDPOINT)
+                .buildAsyncClient();
+
+        } else {
+            client = new OpenAIClientBuilder()
+                .credential(new KeyCredential(CLIENT_KEY))
+                .buildAsyncClient();
+        }
+
+        ChatCompletionService openAIChatCompletion = OpenAIChatCompletion.builder()
+            .withModelId(MODEL_ID)
+            .withOpenAIAsyncClient(client)
+            .build();
+
+        Builder kernelBuilder = Kernel.builder()
+            .withAIService(ChatCompletionService.class, openAIChatCompletion);
+
+        getUsageAsync(kernelBuilder.build());
+        getRenderedPromptAsync(kernelBuilder.build());
+        changingResultAsync(kernelBuilder.build());
+        beforeInvokeCancellationAsync(kernelBuilder.build());
+        afterInvokeCancellationAsync(kernelBuilder.build());
+        chatCompletionHook(kernelBuilder.build());
+        invocationHook(kernelBuilder.build());
+    }
+
+
+    /// <summary>
+    /// Demonstrate using kernel invocation-hooks to monitor usage:
+    /// <see cref="Kernel.FunctionInvoking"/>
+    /// <see cref="Kernel.FunctionInvoked"/>
+    /// </summary>
+    private static void getUsageAsync(Kernel kernel) {
+        System.out.println("\n======== Get Usage Data ========\n");
+
+        // Initialize prompt
+        String functionPrompt = "Write a random paragraph about: {{$input}}.";
+
+        var excuseFunction = KernelFunctionFromPrompt.builder()
+            .withTemplate(functionPrompt)
+            .withName("Excuse")
+            .withDefaultExecutionSettings(PromptExecutionSettings
+                .builder()
+                .withMaxTokens(100)
+                .withTemperature(0.4)
+                .withTopP(1)
+                .build())
+            .build();
+
+        FunctionInvokingHook preHook = event -> {
+            System.out.println(
+                event.getFunction().getName() + " : Pre Execution Handler - Triggered");
+            return event;
+        };
+
+        FunctionInvokingHook removedPreExecutionHandler = event -> {
+            System.out.println(
+                event.getFunction().getName() + " : Pre Execution Handler - Should not trigger");
+            return event;
+        };
+
+        FunctionInvokedHook postExecutionHandler = event -> {
+            System.out.println(
+                event.getFunction().getName() + " : Post Execution Handler - Usage: " + event
+                    .getResult()
+                    .getMetadata()
+                    .getUsage()
+                    .getTotalTokens());
+            return event;
+        };
+
+        kernel.getHookService().addHook(preHook);
+
+        // Demonstrate pattern for removing a handler.
+        kernel.getHookService().addHook("pre-invoke-removed", removedPreExecutionHandler);
+        kernel.getHookService().removeHook("pre-invoke-removed");
+
+        kernel.getHookService().addHook(postExecutionHandler);
+
+        // Invoke prompt to trigger execution hooks.
+        String input = "I missed the F1 final race";
+        var result = kernel.invokeAsync(
+                excuseFunction,
+                KernelArguments
+                    .builder()
+                    .withVariable("input", input)
+                    .build(),
+                String.class)
+            .block();
+        System.out.println("Function Result: " + result.getResult());
+    }
+
+
+    /// <summary>
+    /// Demonstrate using kernel-hooks to around prompt rendering:
+    /// <see cref="Kernel.PromptRendering"/>
+    /// <see cref="Kernel.PromptRendered"/>
+    /// </summary>
+    private static void getRenderedPromptAsync(Kernel kernel) {
+        System.out.println("\n======== Get Rendered Prompt ========\n");
+
+        // Initialize prompt
+        String functionPrompt = "Write a random paragraph about: {{$input}} in the style of {{$style}}.";
+
+        var excuseFunction = KernelFunctionFromPrompt.builder()
+            .withTemplate(functionPrompt)
+            .withName("Excuse")
+            .withDefaultExecutionSettings(PromptExecutionSettings
+                .builder()
+                .withMaxTokens(100)
+                .withTemperature(0.4)
+                .withTopP(1)
+                .build())
+            .build();
+
+        PromptRenderingHook myRenderingHandler = event -> {
+            System.out.println(
+                event.getFunction().getName() + " : Prompt Rendering Handler - Triggered");
+            event.getArguments().put("style", ContextVariable.of("Seinfeld"));
+            return event;
+        };
+
+        PromptRenderedHook myRenderedHandler = event -> {
+            System.out.println(
+                event.getFunction().getName() + " : Prompt Rendered Handler - Triggered");
+
+            String prompt = event.getPrompt() + "\nUSE SHORT, CLEAR, COMPLETE SENTENCES.";
+
+            return new PromptRenderedEvent(
+                event.getFunction(),
+                event.getArguments(),
+                prompt
+            );
+        };
+        kernel.getHookService().addHook(myRenderingHandler);
+        kernel.getHookService().addHook(myRenderedHandler);
+
+        // Invoke prompt to trigger execution hooks.
+        String input = "I missed the F1 final race";
+        var result = kernel.invokeAsync(excuseFunction,
+                KernelArguments
+                    .builder()
+                    .withVariable("input", input)
+                    .build(),
+                String.class)
+            .block();
+        System.out.println("Function Result: " + result.getResult());
+    }
+
+
+    /// <summary>
+    /// Demonstrate using kernel invocation-hooks to post process result:
+    /// <see cref="Kernel.FunctionInvoked"/>
+    /// </summary>
+    private static void changingResultAsync(Kernel kernel) {
+        System.out.println("\n======== Changing/Filtering Function Result ========\n");
+
+        // Initialize function
+        String functionPrompt = "Write a paragraph about Handlers.";
+
+        var writerFunction = KernelFunctionFromPrompt.builder()
+            .withTemplate(functionPrompt)
+            .withName("Writer")
+            .withDefaultExecutionSettings(PromptExecutionSettings
+                .builder()
+                .withMaxTokens(100)
+                .withTemperature(0.4)
+                .withTopP(1)
+                .build())
+            .build();
+
+        FunctionInvokedHook hook = event -> {
+            String result = (String) event.getResult().getResult();
+            result = result.replaceAll("[aeiouAEIOU0-9]", "*");
+
+            return new FunctionInvokedEvent<>(
+                event.getFunction(),
+                event.getArguments(),
+                new FunctionResult<>(
+                    ContextVariable.of(result),
+                    event.getResult().getMetadata()
+                )
+            );
+        };
+        kernel.getHookService().addHook(hook);
+
+        // Invoke prompt to trigger execution hooks.
+        var result = kernel.invokeAsync(
+                writerFunction,
+                KernelArguments.builder().build(),
+                String.class)
+            .block();
+        System.out.println("Function Result: " + result.getResult());
+    }
+
+
+    /// <summary>
+    /// Demonstrate using kernel invocation-hooks to cancel prior to execution:
+    /// <see cref="Kernel.FunctionInvoking"/>
+    /// <see cref="Kernel.FunctionInvoked"/>
+    /// </summary>
+    private static void beforeInvokeCancellationAsync(Kernel kernel) {
+        System.out.println("\n======== Cancelling Pipeline Execution - Invoking event ========\n");
+
+        // Initialize prompt
+        String functionPrompt = "Write a paragraph about: Cancellation.";
+
+        var writerFunction = KernelFunctionFromPrompt.builder()
+            .withTemplate(functionPrompt)
+            .withName("Writer")
+            .withDefaultExecutionSettings(PromptExecutionSettings
+                .builder()
+                .withMaxTokens(1000)
+                .withTemperature(1)
+                .withTopP(0.5)
+                .build())
+            .build();
+
+        FunctionInvokingHook hook = event -> {
+            System.out.println(
+                event.getFunction().getName()
+                    + " : FunctionInvoking - Cancelling before execution");
+            throw new RuntimeException("Cancelled");
+        };
+
+        kernel.getHookService().addHook(hook);
+
+        try {
+            // Invoke prompt to trigger execution hooks.
+            var result = kernel.invokeAsync(
+                    writerFunction,
+                    KernelArguments.builder().build(),
+                    String.class)
+                .block();
+            System.out.println("Function Result: " + result.getResult());
+        } catch (Exception e) {
+            System.out.println("Exception: " + e.getMessage());
+        }
+    }
+
+
+    /// <summary>
+    /// Demonstrate using kernel invocation-hooks to cancel post after execution:
+    /// <see cref="Kernel.FunctionInvoking"/>
+    /// <see cref="Kernel.FunctionInvoked"/>
+    /// </summary>
+    private static void afterInvokeCancellationAsync(Kernel kernel) {
+        System.out.println("\n======== Cancelling Pipeline Execution - Invoked event ========\n");
+
+        // Initialize prompts
+        var firstFunction = KernelFunctionFromPrompt.create("Write a phrase with Invoke.");
+        var secondFunction = KernelFunctionFromPrompt.create("Write a phrase with Cancellation.");
+
+        AtomicInteger invokingCounter = new AtomicInteger(0);
+        kernel.getHookService().addHook((FunctionInvokingHook) event -> {
+            invokingCounter.incrementAndGet();
+            return event;
+        });
+
+        AtomicInteger invokedCounter = new AtomicInteger(0);
+        kernel.getHookService().addHook((FunctionInvokedHook) event -> {
+            invokedCounter.incrementAndGet();
+            throw new RuntimeException("Cancelled");
+        });
+
+        // Invoke prompt to trigger execution hooks.
+        try {
+            var result = kernel.invokeAsync(
+                    secondFunction,
+                    KernelArguments.builder().build(),
+                    String.class)
+                .block();
+            System.out.println("Function Result: " + result.getResult());
+        } catch (Exception e) {
+            System.out.println("Exception: " + e.getMessage());
+            System.out.println("Function Invoked Times: " + invokedCounter.get());
+            System.out.println("Function Invoking Times: " + invokedCounter.get());
+        }
+    }
+
+    private static void chatCompletionHook(Kernel kernel) {
+        // Initialize prompt
+        String functionPrompt = "Write a paragraph about hats";
+
+        var writerFunction = KernelFunctionFromPrompt.builder()
+            .withTemplate(functionPrompt)
+            .withName("Writer")
+            .withDefaultExecutionSettings(PromptExecutionSettings
+                .builder()
+                .withMaxTokens(1000)
+                .withTemperature(1)
+                .withTopP(0.5)
+                .build())
+            .build();
+
+        kernel.getHookService().addPreChatCompletionHook(event -> {
+            ChatCompletionsOptions options = event.getOptions();
+            List<ChatRequestMessage> messages = options.getMessages();
+
+            messages = new ArrayList<>(messages);
+            messages.add(
+                new ChatRequestSystemMessage("Use upper case text when responding to the prompt."));
+
+            return new PreChatCompletionEvent(
+                PreChatCompletionHook.cloneOptionsWithMessages(options, messages)
+            );
+        });
+
+        try {
+            // Invoke prompt to trigger execution hooks.
+            var result = kernel.invokeAsync(
+                    writerFunction,
+                    KernelArguments.builder().build(),
+                    String.class)
+                .block();
+            System.out.println("Function Result: " + result.getResult());
+        } catch (Exception e) {
+            System.out.println("Exception: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Show use of hooks added on a single invocations.
+     *
+     * @param kernel
+     */
+    private static void invocationHook(Kernel kernel) {
+        // Initialize prompt
+        String functionPrompt = "Write a paragraph about hats";
+
+        var writerFunction = KernelFunctionFromPrompt.builder()
+            .withTemplate(functionPrompt)
+            .withName("Writer")
+            .withDefaultExecutionSettings(PromptExecutionSettings
+                .builder()
+                .withMaxTokens(1000)
+                .withTemperature(1)
+                .withTopP(0.5)
+                .build())
+            .build();
+
+        KernelHooks kernelHooks = new KernelHooks();
+        kernelHooks.addPreChatCompletionHook(event -> {
+            ChatCompletionsOptions options = event.getOptions();
+            List<ChatRequestMessage> messages = options.getMessages();
+
+            messages = new ArrayList<>(messages);
+            messages.add(
+                new ChatRequestSystemMessage("Use upper case text when responding to the prompt."));
+
+            return new PreChatCompletionEvent(
+                PreChatCompletionHook.cloneOptionsWithMessages(options, messages)
+            );
+        });
+
+        try {
+            // Invoke prompt to trigger execution hooks.
+            var result = kernel.invokeAsync(
+                    writerFunction,
+                    KernelArguments.builder().build(),
+                    kernelHooks,
+                    String.class)
+                .block();
+            System.out.println("Function Result: " + result.getResult());
+        } catch (Exception e) {
+            System.out.println("Exception: " + e.getMessage());
+        }
+    }
+}

java/samples/sample-code/src/main/java/com/microsoft/semantickernel/samples/syntaxexamples/Example62_CustomAIServiceSelector.java

@@ -90,8 +90,8 @@ public class Example62_CustomAIServiceSelector {
 
         @Nullable
         @Override
-        public AIServiceSelection trySelectAIService(
-            Class<? extends AIService> serviceType,
+        public <T extends AIService> AIServiceSelection<T> trySelectAIService(
+            Class<T> serviceType,
 
             @Nullable
             KernelFunction function,

java/samples/sk-v1/01-SimpleChat/src/main/java/Main.java

@@ -43,7 +43,6 @@ public class Main {
 
         Kernel kernel = Kernel.builder()
             .withAIService(ChatCompletionService.class, gpt35Turbo)
-            .withPromptTemplate(new HandlebarsPromptTemplate())
             .build();
 
         // Initialize the required functions and services for the kernel

java/samples/sk-v1/01-SimpleChat/src/test/java/SimpleChatTest.java

@@ -3,11 +3,10 @@ import com.microsoft.semantickernel.chatcompletion.AuthorRole;
 import com.microsoft.semantickernel.chatcompletion.ChatCompletionService;
 import com.microsoft.semantickernel.chatcompletion.ChatHistory;
 import com.microsoft.semantickernel.chatcompletion.ChatMessageContent;
+import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.KernelFunction;
 import com.microsoft.semantickernel.orchestration.KernelFunctionYaml;
-import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
-import com.microsoft.semantickernel.templateengine.handlebars.HandlebarsPromptTemplate;
 import java.io.IOException;
 import java.nio.file.Path;
 import java.util.Arrays;
@@ -65,7 +64,6 @@ public class SimpleChatTest {
         throws IOException {
         Kernel kernel = Kernel.builder()
             .withAIService(ChatCompletionService.class, gpt35Turbo)
-            .withPromptTemplate(new HandlebarsPromptTemplate())
             .build();
 
         // Initialize the required functions and services for the kernel

java/samples/sk-v1/02-PersonaChat/src/main/java/Main.java

@@ -41,7 +41,6 @@ public class Main {
 
         Kernel kernel = Kernel.builder()
             .withAIService(ChatCompletionService.class, gpt35Turbo)
-            .withPromptTemplate(new HandlebarsPromptTemplate())
             .build();
 
         ChatHistory chatHistory = new ChatHistory();

java/samples/sk-v1/02-PersonaChat/src/test/java/PersonaChatTest.java

@@ -59,7 +59,6 @@ public class PersonaChatTest {
 
         Kernel kernel = Kernel.builder()
             .withAIService(ChatCompletionService.class, gpt35Turbo)
-            .withPromptTemplate(new HandlebarsPromptTemplate())
             .build();
 
         // Initialize the required functions and services for the kernel

java/samples/sk-v1/03-SimpleRag/src/main/java/Main.java

@@ -49,7 +49,6 @@ public class Main {
 
         Kernel kernel = Kernel.builder()
             .withAIService(ChatCompletionService.class, gpt35Turbo)
-            .withPromptTemplate(new HandlebarsPromptTemplate())
             .withPlugin(searchPlugin)
             .build();
 

java/samples/sk-v1/03-SimpleRag/src/test/java/SimpleRagTest.java

@@ -72,7 +72,6 @@ public class SimpleRagTest {
 
         Kernel kernel = Kernel.builder()
             .withAIService(ChatCompletionService.class, gpt35Turbo)
-            .withPromptTemplate(new HandlebarsPromptTemplate())
             .withPlugin(searchPlugin)
             .build();
 

java/semantickernel-api/pom.xml

@@ -66,5 +66,9 @@
             <artifactId>junit-jupiter-api</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.github.spotbugs</groupId>
+            <artifactId>spotbugs-annotations</artifactId>
+        </dependency>
     </dependencies>
 </project>

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/AIService.java

@@ -2,6 +2,7 @@
 package com.microsoft.semantickernel;
 
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariable;
+import javax.annotation.Nullable;
 import java.util.Map;
 
 /**
@@ -50,6 +51,7 @@ public interface AIService {
     /// <summary>
     /// Gets the specified attribute.
     /// </summary>
+    @Nullable
     static String getAttribute(AIService service, String key)
     {
         if (service.getAttributes() != null) {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/Kernel.java

@@ -3,6 +3,7 @@ package com.microsoft.semantickernel;
 
 import com.microsoft.semantickernel.builders.Buildable;
 import com.microsoft.semantickernel.builders.SemanticKernelBuilder;
+import com.microsoft.semantickernel.hooks.KernelHooks;
 import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.KernelFunction;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariableType;
@@ -12,13 +13,16 @@ import com.microsoft.semantickernel.orchestration.contextvariables.KernelArgumen
 import com.microsoft.semantickernel.plugin.KernelPlugin;
 import com.microsoft.semantickernel.plugin.KernelPluginCollection;
 import com.microsoft.semantickernel.semanticfunctions.PromptTemplate;
+import com.microsoft.semantickernel.services.AIServiceSelection;
 import com.microsoft.semantickernel.services.AIServiceSelector;
 import com.microsoft.semantickernel.services.OrderedAIServiceSelector;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 import javax.annotation.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -33,23 +37,37 @@ public class Kernel implements Buildable {
 
     private final AIServiceSelector serviceSelector;
     private final KernelPluginCollection plugins;
+    private final KernelHooks kernelHooks;
 
     public Kernel(
         AIServiceSelector serviceSelector,
-        @Nullable KernelPluginCollection plugins) {
+        @Nullable KernelPluginCollection plugins,
+        @Nullable KernelHooks kernelHooks) {
         this.serviceSelector = serviceSelector;
+
         if (plugins != null) {
-            this.plugins = plugins;
+            this.plugins = new KernelPluginCollection(plugins.getPlugins());
         } else {
             this.plugins = new KernelPluginCollection();
         }
+
+        this.kernelHooks = new KernelHooks(kernelHooks);
+    }
+
+    public <T> Mono<FunctionResult<T>> invokeAsync(
+        KernelFunction function,
+        @Nullable KernelArguments arguments,
+        @Nullable KernelHooks kernelHooks,
+        ContextVariableType<T> resultType) {
+        kernelHooks = mergeInGlobalHooks(kernelHooks);
+        return function.invokeAsync(this, arguments, kernelHooks, resultType);
     }
 
     public <T> Mono<FunctionResult<T>> invokeAsync(
         KernelFunction function,
         @Nullable KernelArguments arguments,
         ContextVariableType<T> resultType) {
-        return function.invokeAsync(this, arguments, resultType);
+        return invokeAsync(function, arguments, null, resultType);
     }
 
 
@@ -57,16 +75,29 @@ public class Kernel implements Buildable {
         String pluginName,
         String functionName,
         @Nullable KernelArguments arguments,
+        @Nullable KernelHooks kernelHooks,
         ContextVariableType<T> resultType) {
+        kernelHooks = mergeInGlobalHooks(kernelHooks);
         return plugins.getFunction(pluginName, functionName)
-            .invokeAsync(this, arguments, resultType);
+            .invokeAsync(this, arguments, kernelHooks, resultType);
+    }
+
+    public <T> Mono<FunctionResult<T>> invokeAsync(
+        String pluginName,
+        String functionName,
+        @Nullable KernelArguments arguments,
+        ContextVariableType<T> resultType) {
+        return invokeAsync(pluginName, functionName, arguments, null, resultType);
     }
 
     public <T> Mono<FunctionResult<T>> invokeAsync(
         KernelFunction function,
         @Nullable KernelArguments arguments,
+        @Nullable KernelHooks kernelHooks,
         Class<T> resultType) {
 
+        kernelHooks = mergeInGlobalHooks(kernelHooks);
+
         ContextVariableType<T> contextVariable;
 
         try {
@@ -80,39 +111,72 @@ public class Kernel implements Buildable {
                 throw e;
             }
         }
-        return function.invokeAsync(this, arguments, contextVariable);
+        return function.invokeAsync(this, arguments, kernelHooks, contextVariable);
+    }
+
+    public <T> Mono<FunctionResult<T>> invokeAsync(
+        KernelFunction function,
+        @Nullable KernelArguments arguments,
+        Class<T> resultType) {
+        return invokeAsync(function, arguments, null, resultType);
+    }
+
+    private KernelHooks mergeInGlobalHooks(@Nullable KernelHooks kernelHooks) {
+        KernelHooks allKernelHooks = this.kernelHooks;
+        if (kernelHooks != null) {
+            allKernelHooks = allKernelHooks.append(kernelHooks);
+        }
+        return allKernelHooks;
     }
 
     public List<KernelFunction> getFunctions() {
-        return null;
+        return plugins.getPlugins()
+            .stream()
+            .map(KernelPlugin::getFunctions)
+            .flatMap(m -> m.values().stream())
+            .collect(Collectors.toList());
     }
 
     public AIServiceSelector getServiceSelector() {
         return serviceSelector;
     }
 
+    @SuppressFBWarnings("EI_EXPOSE_REP")
     public KernelPluginCollection getPlugins() {
         return plugins;
     }
 
-    public <T extends AIService> T getService(Class<T> clazz) {
-        return (T) serviceSelector
+
+    @SuppressFBWarnings("EI_EXPOSE_REP")
+    public KernelHooks getHookService() {
+        return kernelHooks;
+    }
+
+    public <T extends AIService> T getService(Class<T> clazz) throws ServiceNotFoundException {
+        AIServiceSelection<T> selector = serviceSelector
             .trySelectAIService(
                 clazz,
                 null,
                 null
-            )
-            .getService();
+            );
+
+        if (selector == null) {
+            throw new ServiceNotFoundException("Unable to find service of type " + clazz.getName());
+        }
+
+        return selector.getService();
     }
 
     public static Kernel.Builder builder() {
         return new Kernel.Builder();
     }
 
+
     public static class Builder implements SemanticKernelBuilder<Kernel> {
 
         private final Map<Class<? extends AIService>, AIService> services = new HashMap<>();
         private final List<KernelPlugin> plugins = new ArrayList<>();
+        @Nullable
         private Function<Map<Class<? extends AIService>, AIService>, AIServiceSelector> serviceSelectorProvider;
 
         public <T extends AIService> Builder withAIService(Class<T> clazz, T aiService) {
@@ -147,7 +211,8 @@ public class Kernel implements Buildable {
 
             return new Kernel(
                 serviceSelector,
-                new KernelPluginCollection(plugins));
+                new KernelPluginCollection(plugins),
+                null);
         }
     }
 

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/ServiceNotFoundException.java

@@ -0,0 +1,10 @@
+package com.microsoft.semantickernel;
+
+import com.microsoft.semantickernel.exceptions.SKCheckedException;
+
+public class ServiceNotFoundException extends SKCheckedException {
+
+    public ServiceNotFoundException(String s) {
+        super(s);
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/chatcompletion/ChatCompletionService.java

@@ -8,6 +8,7 @@ import com.microsoft.semantickernel.TextAIService;
 import com.microsoft.semantickernel.builders.Buildable;
 import com.microsoft.semantickernel.builders.SemanticKernelBuilder;
 import com.microsoft.semantickernel.builders.ServiceLoadUtil;
+import com.microsoft.semantickernel.hooks.KernelHooks;
 import com.microsoft.semantickernel.orchestration.PromptExecutionSettings;
 import java.util.List;
 import reactor.core.publisher.Mono;
@@ -26,6 +27,20 @@ public interface ChatCompletionService extends Buildable, TextAIService {
         Kernel kernel
     );
 
+    Mono<List<ChatMessageContent>> getChatMessageContentsAsync(
+        ChatHistory chatHistory,
+        PromptExecutionSettings promptExecutionSettings,
+        Kernel kernel,
+        KernelHooks kernelHooks
+    );
+
+    Mono<List<ChatMessageContent>> getChatMessageContentsAsync(
+        String prompt,
+        PromptExecutionSettings promptExecutionSettings,
+        Kernel kernel,
+        KernelHooks kernelHooks
+    );
+
     static Builder builder() {
         return ServiceLoadUtil.findServiceLoader(Builder.class,
                 "com.microsoft.semantickernel.aiservices.openai.chatcompletion.OpenAIChatCompletion$Builder")

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/chatcompletion/ChatMessageContent.java

@@ -3,11 +3,11 @@ package com.microsoft.semantickernel.chatcompletion;
 
 import com.microsoft.semantickernel.KernelContent;
 import com.microsoft.semantickernel.orchestration.FunctionResultMetadata;
-import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariable;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
-import java.util.Map;
 import javax.annotation.Nullable;
 
 public class ChatMessageContent extends KernelContent<ChatMessageContent> {
@@ -61,7 +61,7 @@ public class ChatMessageContent extends KernelContent<ChatMessageContent> {
         super(innerContent, modelId, metadata);
         this.authorRole = authorRole;
         this.encoding = encoding != null ? encoding : StandardCharsets.UTF_8;
-        this.items = items;
+        this.items = new ArrayList<>(items);
     }
 
     public AuthorRole getAuthorRole() {
@@ -81,11 +81,11 @@ public class ChatMessageContent extends KernelContent<ChatMessageContent> {
     }
 
     public List<KernelContent> getItems() {
-        return items;
+        return Collections.unmodifiableList(items);
     }
 
     public void setItems(List<KernelContent> items) {
-        this.items = items;
+        this.items = new ArrayList<>(items);
     }
 
     @Nullable

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/FunctionInvokedEvent.java

@@ -0,0 +1,31 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.microsoft.semantickernel.orchestration.FunctionResult;
+import com.microsoft.semantickernel.orchestration.KernelFunction;
+import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
+
+public class FunctionInvokedEvent<T> implements KernelHookEvent {
+
+    private final KernelFunction function;
+    private final KernelArguments arguments;
+    private final FunctionResult<T> result;
+
+    public FunctionInvokedEvent(KernelFunction function, KernelArguments arguments,
+        FunctionResult<T> result) {
+        this.function = function;
+        this.arguments = arguments;
+        this.result = result;
+    }
+
+    public KernelFunction getFunction() {
+        return function;
+    }
+
+    public KernelArguments getArguments() {
+        return arguments;
+    }
+
+    public FunctionResult<T> getResult() {
+        return result;
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/FunctionInvokingEvent.java

@@ -0,0 +1,23 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.microsoft.semantickernel.orchestration.KernelFunction;
+import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
+
+public class FunctionInvokingEvent implements KernelHookEvent {
+
+    private final KernelFunction function;
+    private final KernelArguments arguments;
+
+    public FunctionInvokingEvent(KernelFunction function, KernelArguments arguments) {
+        this.function = function;
+        this.arguments = arguments;
+    }
+
+    public KernelFunction getFunction() {
+        return function;
+    }
+
+    public KernelArguments getArguments() {
+        return arguments;
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/KernelHook.java

@@ -0,0 +1,79 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.azure.ai.openai.models.ChatCompletionsOptions;
+import com.azure.ai.openai.models.ChatRequestMessage;
+import java.util.List;
+import java.util.function.Function;
+import java.util.function.Predicate;
+
+public interface KernelHook<T extends KernelHookEvent> extends Predicate<KernelHookEvent>, Function<T, T> {
+
+    interface FunctionInvokingHook extends KernelHook<FunctionInvokingEvent> {
+
+        @Override
+        default boolean test(KernelHookEvent arguments) {
+            return FunctionInvokingEvent.class.isAssignableFrom(arguments.getClass());
+        }
+    }
+
+    interface FunctionInvokedHook extends KernelHook<FunctionInvokedEvent> {
+
+        @Override
+        default boolean test(KernelHookEvent arguments) {
+            return FunctionInvokedEvent.class.isAssignableFrom(arguments.getClass());
+        }
+    }
+
+    interface PromptRenderingHook extends KernelHook<PromptRenderingEvent> {
+
+        @Override
+        default boolean test(KernelHookEvent arguments) {
+            return PromptRenderingEvent.class.isAssignableFrom(arguments.getClass());
+        }
+    }
+
+    interface PromptRenderedHook extends KernelHook<PromptRenderedEvent> {
+
+        @Override
+        default boolean test(KernelHookEvent arguments) {
+            return PromptRenderedEvent.class.isAssignableFrom(arguments.getClass());
+        }
+    }
+
+    interface PreChatCompletionHook extends KernelHook<PreChatCompletionEvent> {
+
+        @Override
+        default boolean test(KernelHookEvent arguments) {
+            return PreChatCompletionEvent.class.isAssignableFrom(arguments.getClass());
+        }
+
+        static ChatCompletionsOptions cloneOptionsWithMessages(
+            ChatCompletionsOptions options,
+            List<ChatRequestMessage> messages) {
+            ChatCompletionsOptions newOptions = new ChatCompletionsOptions(messages)
+                .setPresencePenalty(options.getPresencePenalty())
+                .setFrequencyPenalty(options.getFrequencyPenalty())
+                .setLogitBias(options.getLogitBias())
+                .setMaxTokens(options.getMaxTokens())
+                .setModel(options.getModel())
+                .setStop(options.getStop())
+                .setTemperature(options.getTemperature())
+                .setTools(options.getTools())
+                .setTopP(options.getTopP())
+                .setUser(options.getUser())
+                .setDataSources(options.getDataSources())
+                .setEnhancements(options.getEnhancements())
+                .setFunctions(options.getFunctions())
+                .setN(options.getN())
+                .setResponseFormat(options.getResponseFormat())
+                .setSeed(options.getSeed())
+                .setStream(options.isStream())
+                .setToolChoice(options.getToolChoice());
+
+            if (options.getFunctionCall() != null) {
+                newOptions = newOptions.setFunctionCall(options.getFunctionCall());
+            }
+            return newOptions;
+        }
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/KernelHookEvent.java

@@ -0,0 +1,5 @@
+package com.microsoft.semantickernel.hooks;
+
+public interface KernelHookEvent {
+
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/KernelHooks.java

@@ -0,0 +1,93 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.microsoft.semantickernel.hooks.KernelHook.FunctionInvokedHook;
+import com.microsoft.semantickernel.hooks.KernelHook.FunctionInvokingHook;
+import com.microsoft.semantickernel.hooks.KernelHook.PreChatCompletionHook;
+import com.microsoft.semantickernel.hooks.KernelHook.PromptRenderedHook;
+import com.microsoft.semantickernel.hooks.KernelHook.PromptRenderingHook;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.function.Function;
+import javax.annotation.Nullable;
+
+public class KernelHooks {
+
+    private final Map<String, KernelHook<?>> hooks;
+
+    public KernelHooks() {
+        this.hooks = new HashMap<>();
+    }
+
+    public KernelHooks(@Nullable KernelHooks kernelHooks) {
+        if (kernelHooks == null) {
+            this.hooks = new HashMap<>();
+        } else {
+            this.hooks = new HashMap<>(kernelHooks.getHooks());
+        }
+    }
+
+    public KernelHooks(Map<String, KernelHook<?>> hooks) {
+        this.hooks = new HashMap<>(hooks);
+    }
+
+    private Map<String, KernelHook<?>> getHooks() {
+        return Collections.unmodifiableMap(hooks);
+    }
+
+    public String addFunctionInvokingHook(
+        Function<FunctionInvokingEvent, FunctionInvokingEvent> function) {
+        return addHook((FunctionInvokingHook) function::apply);
+    }
+
+    public String addFunctionInvokedHook(
+        Function<FunctionInvokedEvent, FunctionInvokedEvent> function) {
+        return addHook((FunctionInvokedHook) function::apply);
+    }
+
+    public String addPreChatCompletionHook(
+        Function<PreChatCompletionEvent, PreChatCompletionEvent> function) {
+        return addHook((PreChatCompletionHook) function::apply);
+    }
+
+    public String addPromptRenderedHook(
+        Function<PromptRenderedEvent, PromptRenderedEvent> function) {
+        return addHook((PromptRenderedHook) function::apply);
+    }
+
+    public String addPromptRenderingHook(
+        Function<PromptRenderingEvent, PromptRenderingEvent> function) {
+        return addHook((PromptRenderingHook) function::apply);
+    }
+
+    public <T extends KernelHookEvent> T executeHooks(T event) {
+        for (KernelHook<?> hook : hooks.values()) {
+            if (hook.test(event)) {
+                event = ((KernelHook<T>) hook).apply(event);
+            }
+        }
+        return event;
+    }
+
+    public String addHook(KernelHook<?> hook) {
+        return addHook(UUID.randomUUID().toString(), hook);
+    }
+
+    public String addHook(String hookName, KernelHook<?> hook) {
+        hooks.put(hookName, hook);
+        return hookName;
+    }
+
+    public KernelHook<?> removeHook(String hookName) {
+        return hooks.remove(hookName);
+    }
+
+    public KernelHooks append(KernelHooks kernelHooks) {
+        Map<String, KernelHook<?>> newHooks = new HashMap<>(this.hooks);
+        newHooks.putAll(this.hooks);
+        newHooks.putAll(kernelHooks.getHooks());
+
+        return new KernelHooks(newHooks);
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/PreChatCompletionEvent.java

@@ -0,0 +1,16 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.azure.ai.openai.models.ChatCompletionsOptions;
+
+public class PreChatCompletionEvent implements KernelHookEvent {
+
+    private final ChatCompletionsOptions options;
+
+    public PreChatCompletionEvent(ChatCompletionsOptions options) {
+        this.options = options;
+    }
+
+    public ChatCompletionsOptions getOptions() {
+        return options;
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/PromptRenderedEvent.java

@@ -0,0 +1,30 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.microsoft.semantickernel.orchestration.KernelFunction;
+import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
+
+public class PromptRenderedEvent implements KernelHookEvent {
+
+    private final KernelFunction function;
+    private final KernelArguments arguments;
+    private final String prompt;
+
+    public PromptRenderedEvent(KernelFunction function, KernelArguments arguments,
+        String prompt) {
+        this.function = function;
+        this.arguments = arguments;
+        this.prompt = prompt;
+    }
+
+    public KernelFunction getFunction() {
+        return function;
+    }
+
+    public KernelArguments getArguments() {
+        return arguments;
+    }
+
+    public String getPrompt() {
+        return prompt;
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/hooks/PromptRenderingEvent.java

@@ -0,0 +1,23 @@
+package com.microsoft.semantickernel.hooks;
+
+import com.microsoft.semantickernel.orchestration.KernelFunction;
+import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
+
+public class PromptRenderingEvent implements KernelHookEvent {
+
+    private final KernelFunction function;
+    private final KernelArguments arguments;
+
+    public PromptRenderingEvent(KernelFunction function, KernelArguments arguments) {
+        this.function = function;
+        this.arguments = arguments;
+    }
+
+    public KernelFunction getFunction() {
+        return function;
+    }
+
+    public KernelArguments getArguments() {
+        return arguments;
+    }
+}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/DefaultKernelFunction.java

@@ -1,5 +1,6 @@
 package com.microsoft.semantickernel.orchestration;
 
+import java.util.Collections;
 import java.util.Map;
 import javax.annotation.Nullable;
 
@@ -64,6 +65,10 @@ public abstract class DefaultKernelFunction implements KernelFunction {
     @Override
     @Nullable
     public Map<String, PromptExecutionSettings> getExecutionSettings() {
-        return executionSettings;
+        if (executionSettings != null) {
+            return Collections.unmodifiableMap(executionSettings);
+        } else {
+            return null;
+        }
     }
 }

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/FunctionResultMetadata.java

@@ -15,7 +15,7 @@ public class FunctionResultMetadata {
     private final CaseInsensitiveMap<ContextVariable<?>> metadata;
 
     public FunctionResultMetadata(CaseInsensitiveMap<ContextVariable<?>> metadata) {
-        this.metadata = metadata;
+        this.metadata = new CaseInsensitiveMap<>(metadata);
     }
 
     public static FunctionResultMetadata build(

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/KernelFunction.java

@@ -3,6 +3,7 @@ package com.microsoft.semantickernel.orchestration;
 
 import com.microsoft.semantickernel.Kernel;
 import com.microsoft.semantickernel.builders.Buildable;
+import com.microsoft.semantickernel.hooks.KernelHooks;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariableType;
 import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
 import com.microsoft.semantickernel.semanticfunctions.InputVariable;
@@ -81,6 +82,12 @@ public interface KernelFunction extends Buildable {
         @Nullable KernelArguments arguments,
         ContextVariableType<T> variableType);
 
+    <T> Mono<FunctionResult<T>> invokeAsync(
+        Kernel kernel,
+        @Nullable KernelArguments arguments,
+        KernelHooks kernelHooks,
+        ContextVariableType<T> variableType);
+
     @Nullable
     Map<String, PromptExecutionSettings> getExecutionSettings();
 
@@ -92,8 +99,6 @@ public interface KernelFunction extends Buildable {
 
         FromPromptBuilder withPromptTemplate(PromptTemplate promptTemplate);
 
-        FromPromptBuilder withPluginName(String name);
-
         FromPromptBuilder withExecutionSettings(
             Map<String, PromptExecutionSettings> executionSettings);
 

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/KernelFunctionMetadata.java

@@ -2,6 +2,8 @@ package com.microsoft.semantickernel.orchestration;
 
 import com.microsoft.semantickernel.plugin.KernelParameterMetadata;
 import com.microsoft.semantickernel.plugin.KernelReturnParameterMetadata;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 public class KernelFunctionMetadata {
@@ -25,7 +27,7 @@ public class KernelFunctionMetadata {
         KernelReturnParameterMetadata<?> returnParameter) {
         this.name = name;
         this.description = description;
-        this.parameters = parameters;
+        this.parameters = new ArrayList<>(parameters);
         this.returnParameter = returnParameter;
     }
 
@@ -34,7 +36,7 @@ public class KernelFunctionMetadata {
     }
 
     public List<KernelParameterMetadata> getParameters() {
-        return parameters;
+        return Collections.unmodifiableList(parameters);
     }
 
     public String getDescription() {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/KernelFunctionYaml.java

@@ -10,6 +10,7 @@ import com.microsoft.semantickernel.templateengine.handlebars.HandlebarsPromptTe
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import javax.annotation.Nullable;
 
@@ -26,14 +27,14 @@ public class KernelFunctionYaml {
         String yaml,
         @Nullable PromptTemplateFactory promptTemplateFactory
     ) throws IOException {
-        InputStream targetStream = new ByteArrayInputStream(yaml.getBytes());
+        InputStream targetStream = new ByteArrayInputStream(yaml.getBytes(StandardCharsets.UTF_8));
         return fromYaml(targetStream, promptTemplateFactory);
     }
 
     public static KernelFunction fromPromptYaml(
         String yaml
     ) throws IOException {
-        InputStream targetStream = new ByteArrayInputStream(yaml.getBytes());
+        InputStream targetStream = new ByteArrayInputStream(yaml.getBytes(StandardCharsets.UTF_8));
         return fromYaml(targetStream, null);
     }
 
@@ -62,7 +63,6 @@ public class KernelFunctionYaml {
             .withName(functionModel.getName())
             .withInputParameters(functionModel.getInputVariables())
             .withPromptTemplate(promptTemplate)
-            .withPluginName(functionModel.getName()) // TODO: 1.0 add plugin name
             .withExecutionSettings(functionModel.getExecutionSettings())
             .withDescription(functionModel.getDescription())
             .withOutputVariable(functionModel.getOutputVariable())

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/MethodDetails.java

@@ -1,8 +1,10 @@
 package com.microsoft.semantickernel.orchestration;
 
-import com.microsoft.semantickernel.semanticfunctions.KernelFunctionFromMethod.ImplementationFunc;
 import com.microsoft.semantickernel.plugin.KernelParameterMetadata;
 import com.microsoft.semantickernel.plugin.KernelReturnParameterMetadata;
+import com.microsoft.semantickernel.semanticfunctions.KernelFunctionFromMethod.ImplementationFunc;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 public class MethodDetails {
@@ -22,7 +24,7 @@ public class MethodDetails {
         this.name = name;
         this.description = description;
         this.function = function;
-        this.parameters = parameters;
+        this.parameters = new ArrayList<>(parameters);
         this.returnParameter = returnParameter;
     }
 
@@ -39,7 +41,7 @@ public class MethodDetails {
     }
 
     public List<KernelParameterMetadata> getParameters() {
-        return parameters;
+        return Collections.unmodifiableList(parameters);
     }
 
     public KernelReturnParameterMetadata getReturnParameter() {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/PromptExecutionSettings.java

@@ -1,22 +1,20 @@
 package com.microsoft.semantickernel.orchestration;
 
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-
 import javax.annotation.Nullable;
 
-import com.fasterxml.jackson.annotation.JsonCreator;
-import com.fasterxml.jackson.annotation.JsonIgnore;
-import com.fasterxml.jackson.annotation.JsonProperty;
-
 public class PromptExecutionSettings {
 
     public static final String DEFAULT_SERVICE_ID = "default";
     public static final int DEFAULT_MAX_TOKENS = 256;
-    public static final double DEFAULT_TEMPERATURE= 1.0;
+    public static final double DEFAULT_TEMPERATURE = 1.0;
     public static final double DEFAULT_TOP_P = 1.0;
     public static final double DEFAULT_PRESENCE_PENALTY = 0.0;
     public static final double DEFAULT_FREQUENCY_PENALTY = 0.0;
@@ -56,12 +54,15 @@ public class PromptExecutionSettings {
     private final int bestOf;
     private final int resultsPerPrompt;
     private final String user;
+    @Nullable
     private final List<String> stopSequences;
+    @Nullable
     private final ToolCallBehavior toolCallBehavior;
 
     /// <summary>
     /// Modify the likelihood of specified tokens appearing in the completion.
     /// </summary>s
+    @Nullable
     public Map<Integer, Integer> tokenSelectionBiases;
 
     @JsonCreator
@@ -76,22 +77,24 @@ public class PromptExecutionSettings {
         @JsonProperty(RESULTS_PER_PROMPT) int resultsPerPrompt,
         @JsonProperty(BEST_OF) int bestOf,
         @JsonProperty(USER) String user,
+        @Nullable
         @JsonProperty(STOP_SEQUENCES) List<String> stopSequences,
+        @Nullable
         @JsonProperty(TOKEN_SELECTION_BIASES) Map<Integer, Integer> tokenSelectionBiases) {
-            this(
-                serviceId, 
-                modelId, 
-                temperature, 
-                topP, 
-                presencePenalty,
-                frequencyPenalty, 
-                maxTokens, 
-                resultsPerPrompt,
-                bestOf, 
-                user, 
-                stopSequences, 
-                tokenSelectionBiases,
-                null);
+        this(
+            serviceId,
+            modelId,
+            temperature,
+            topP,
+            presencePenalty,
+            frequencyPenalty,
+            maxTokens,
+            resultsPerPrompt,
+            bestOf,
+            user,
+            stopSequences,
+            tokenSelectionBiases,
+            null);
     }
 
     public PromptExecutionSettings(
@@ -108,19 +111,23 @@ public class PromptExecutionSettings {
         @Nullable List<String> stopSequences,
         @Nullable Map<Integer, Integer> tokenSelectionBiases,
         @Nullable ToolCallBehavior toolCallBehavior) {
-            this.serviceId = serviceId;
-            this.modelId = modelId;
-            this.temperature = temperature;
-            this.topP = topP;
-            this.presencePenalty = presencePenalty;
-            this.frequencyPenalty = frequencyPenalty;
-            this.maxTokens = maxTokens;
-            this.resultsPerPrompt = resultsPerPrompt;
-            this.bestOf = bestOf;
-            this.user = user;
-            this.stopSequences = stopSequences != null ? stopSequences : Collections.emptyList();
-            this.tokenSelectionBiases = tokenSelectionBiases != null ? tokenSelectionBiases : Collections.emptyMap();   
-            this.toolCallBehavior = toolCallBehavior;    
+        this.serviceId = serviceId;
+        this.modelId = modelId;
+        this.temperature = temperature;
+        this.topP = topP;
+        this.presencePenalty = presencePenalty;
+        this.frequencyPenalty = frequencyPenalty;
+        this.maxTokens = maxTokens;
+        this.resultsPerPrompt = resultsPerPrompt;
+        this.bestOf = bestOf;
+        this.user = user;
+        this.stopSequences =
+            stopSequences != null ? new ArrayList<>(stopSequences) : Collections.emptyList();
+        this.tokenSelectionBiases =
+            tokenSelectionBiases != null ? new HashMap<>(tokenSelectionBiases)
+                : Collections.emptyMap();
+        this.toolCallBehavior =
+            toolCallBehavior != null ? new ToolCallBehavior(toolCallBehavior) : null;
     }
 
     @JsonProperty(SERVICE_ID)
@@ -143,7 +150,7 @@ public class PromptExecutionSettings {
         return topP;
     }
 
-    @JsonProperty(PRESENCE_PENALTY) 
+    @JsonProperty(PRESENCE_PENALTY)
     public double getPresencePenalty() {
         return presencePenalty;
     }
@@ -175,19 +182,30 @@ public class PromptExecutionSettings {
     }
 
     @JsonProperty(STOP_SEQUENCES)
+    @Nullable
     public List<String> getStopSequences() {
-        return stopSequences;
+        if (stopSequences != null) {
+            return Collections.unmodifiableList(stopSequences);
+        }
+        return null;
     }
-    
+
     @JsonProperty(TOKEN_SELECTION_BIASES)
+    @Nullable
     public Map<Integer, Integer> getTokenSelectionBiases() {
-        return tokenSelectionBiases;
+        if (tokenSelectionBiases != null) {
+            return Collections.unmodifiableMap(tokenSelectionBiases);
+        }
+        return null;
     }
 
     @JsonIgnore
     @Nullable
     public ToolCallBehavior getToolCallBehavior() {
-        return toolCallBehavior;
+        if (toolCallBehavior != null) {
+            return new ToolCallBehavior(toolCallBehavior);
+        }
+        return null;
     }
 
     public static Builder builder() {
@@ -265,7 +283,8 @@ public class PromptExecutionSettings {
         @SuppressWarnings("unchecked")
         public Builder withStopSequences(List<String> stopSequences) {
             if (stopSequences != null) {
-                ((List<String>)settings.computeIfAbsent(STOP_SEQUENCES, k -> new ArrayList<>())).addAll(stopSequences);
+                ((List<String>) settings.computeIfAbsent(STOP_SEQUENCES,
+                    k -> new ArrayList<>())).addAll(stopSequences);
             }
             return this;
         }
@@ -273,7 +292,8 @@ public class PromptExecutionSettings {
         @SuppressWarnings("unchecked")
         public Builder withTokenSelectionBiases(Map<Integer, Integer> tokenSelectionBiases) {
             if (tokenSelectionBiases != null) {
-                ((Map<Integer, Integer>)settings.computeIfAbsent(TOKEN_SELECTION_BIASES, k -> new HashMap<>())).putAll(tokenSelectionBiases);   
+                ((Map<Integer, Integer>) settings.computeIfAbsent(TOKEN_SELECTION_BIASES,
+                    k -> new HashMap<>())).putAll(tokenSelectionBiases);
             }
             return this;
         }
@@ -281,19 +301,20 @@ public class PromptExecutionSettings {
         @SuppressWarnings("unchecked")
         public PromptExecutionSettings build() {
             return new PromptExecutionSettings(
-                (String)settings.getOrDefault(SERVICE_ID, ""),
-                (String)settings.getOrDefault(MODEL_ID, ""),
-                (double)settings.getOrDefault(TEMPERATURE, DEFAULT_TEMPERATURE),
-                (double)settings.getOrDefault(TOP_P, DEFAULT_TOP_P),
-                (double)settings.getOrDefault(PRESENCE_PENALTY, DEFAULT_PRESENCE_PENALTY),
-                (double)settings.getOrDefault(FREQUENCY_PENALTY, DEFAULT_FREQUENCY_PENALTY),
-                (int)settings.getOrDefault(MAX_TOKENS, DEFAULT_MAX_TOKENS),
-                (int)settings.getOrDefault(RESULTS_PER_PROMPT, DEFAULT_RESULTS_PER_PROMPT),
-                (int)settings.getOrDefault(BEST_OF, DEFAULT_BEST_OF),
-                (String)settings.getOrDefault(USER, ""),
-                (List<String>)settings.getOrDefault(STOP_SEQUENCES, Collections.emptyList()),
-                (Map<Integer, Integer>)settings.getOrDefault(TOKEN_SELECTION_BIASES, Collections.emptyMap()),
-                (ToolCallBehavior)settings.getOrDefault("toolCallBehavior", new ToolCallBehavior())
+                (String) settings.getOrDefault(SERVICE_ID, ""),
+                (String) settings.getOrDefault(MODEL_ID, ""),
+                (double) settings.getOrDefault(TEMPERATURE, DEFAULT_TEMPERATURE),
+                (double) settings.getOrDefault(TOP_P, DEFAULT_TOP_P),
+                (double) settings.getOrDefault(PRESENCE_PENALTY, DEFAULT_PRESENCE_PENALTY),
+                (double) settings.getOrDefault(FREQUENCY_PENALTY, DEFAULT_FREQUENCY_PENALTY),
+                (int) settings.getOrDefault(MAX_TOKENS, DEFAULT_MAX_TOKENS),
+                (int) settings.getOrDefault(RESULTS_PER_PROMPT, DEFAULT_RESULTS_PER_PROMPT),
+                (int) settings.getOrDefault(BEST_OF, DEFAULT_BEST_OF),
+                (String) settings.getOrDefault(USER, ""),
+                (List<String>) settings.getOrDefault(STOP_SEQUENCES, Collections.emptyList()),
+                (Map<Integer, Integer>) settings.getOrDefault(TOKEN_SELECTION_BIASES,
+                    Collections.emptyMap()),
+                (ToolCallBehavior) settings.getOrDefault("toolCallBehavior", new ToolCallBehavior())
             );
         }
     }

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/TextRequestContent.java

@@ -1,34 +0,0 @@
-package com.microsoft.semantickernel.orchestration;
-
-import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
-
-public class TextRequestContent<T> {
-
-    /// <summary>
-    /// In a scenario of multiple choices per request, this represents zero-based index of the choice in the streaming sequence
-    /// </summary>
-    public int choiceIndex;
-
-    /// <summary>
-    /// The inner content representation. Use this to bypass the current abstraction.
-    /// </summary>
-    /// <remarks>
-    /// The usage of this property is considered "unsafe". Use it only if strictly necessary.
-    /// </remarks>
-    public T innerContent;
-
-    /// <summary>
-    /// The model ID used to generate the content.
-    /// </summary>
-    public String modelId;
-
-    /// <summary>
-    /// The metadata associated with the content.
-    /// </summary>
-    public KernelArguments metadata;
-
-
-    public TextRequestContent(T content) {
-        this.innerContent = content;
-    }
-}

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/ToolCallBehavior.java

@@ -4,7 +4,7 @@ import java.util.HashMap;
 import java.util.Map;
 
 /**
- * Defines the behavior of a tool call. Currently, the only tool available is function calling. 
+ * Defines the behavior of a tool call. Currently, the only tool available is function calling.
  */
 public class ToolCallBehavior {
 
@@ -46,6 +46,12 @@ public class ToolCallBehavior {
     public ToolCallBehavior() {
     }
 
+    public ToolCallBehavior(ToolCallBehavior toolCallBehavior) {
+        flags.putAll(toolCallBehavior.flags);
+        functionSettings.putAll(toolCallBehavior.functionSettings);
+        settings.putAll(toolCallBehavior.settings);
+    }
+
     public ToolCallBehavior kernelFunctions(boolean enable) {
         setFlag("kernelFunctions", enable);
         return this;
@@ -61,7 +67,7 @@ public class ToolCallBehavior {
             String key = FunctionCallBehavior.getKey(function);
             functionSettings.compute(
                 key,
-                (k,v) -> {
+                (k, v) -> {
                     if (v == null) {
                         return new FunctionCallBehavior(function, require, false);
                     } else {
@@ -78,7 +84,7 @@ public class ToolCallBehavior {
             String key = FunctionCallBehavior.getKey(function);
             functionSettings.compute(
                 key,
-                (k,v) -> {
+                (k, v) -> {
                     if (v == null) {
                         return new FunctionCallBehavior(function, false, enable);
                     } else {
@@ -93,7 +99,7 @@ public class ToolCallBehavior {
     public ToolCallBehavior maximumAutoInvokeAttempts(int maximumAutoInvokeAttempts) {
         setSetting("maximumAutoInvokeAttempts", maximumAutoInvokeAttempts);
         return this;
-    }   
+    }
 
     public boolean kernelFunctionsEnabled() {
         return getFlag("kernelFunctions");
@@ -127,7 +133,7 @@ public class ToolCallBehavior {
     }
 
     public boolean functionEnabled(String pluginName, String functionName) {
- 
+
         String key = FunctionCallBehavior.getKey(pluginName, functionName);
         if (functionSettings.containsKey(key)) {
             return functionSettings.get(key).enabled();

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/contextvariables/CaseInsensitiveMap.java

@@ -7,6 +7,7 @@ import java.util.Map;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.stream.Collectors;
+import javax.annotation.Nullable;
 
 public class CaseInsensitiveMap<T> extends HashMap<String, T> {
 
@@ -53,6 +54,7 @@ public class CaseInsensitiveMap<T> extends HashMap<String, T> {
         return super.containsKey(((String) key).toLowerCase(Locale.ROOT));
     }
 
+    @Nullable
     @Override
     public T get(Object key) {
         if (key == null) {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/contextvariables/ContextVariableTypeConverter.java

@@ -1,5 +1,6 @@
 package com.microsoft.semantickernel.orchestration.contextvariables;
 
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
@@ -75,7 +76,7 @@ public class ContextVariableTypeConverter<T> {
         this.fromObject = fromObject;
         this.toPromptString = toPromptString;
         this.fromPromptString = fromPromptString;
-        this.toObjects = toObjects;
+        this.toObjects = new ArrayList<>(toObjects);
     }
 
     
@@ -104,6 +105,7 @@ public class ContextVariableTypeConverter<T> {
         return null;
     }
 
+    @Nullable
     public T fromObject(Object s) {
         if (s == null) {
             return null;
@@ -118,6 +120,7 @@ public class ContextVariableTypeConverter<T> {
         return toPromptString.apply(t);
     }
 
+    @Nullable
     public T fromPromptString(String t) {
         if (t == null) {
             return null;

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/contextvariables/DefaultKernelArguments.java

@@ -2,12 +2,14 @@
 package com.microsoft.semantickernel.orchestration.contextvariables;
 
 import com.microsoft.semantickernel.orchestration.PromptExecutionSettings;
+import reactor.util.annotation.NonNull;
+
+import javax.annotation.Nullable;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
-import javax.annotation.Nullable;
-import reactor.util.annotation.NonNull;
 
 /// <summary>
 /// Context Variables is a data structure that holds temporary data while a task is being performed.
@@ -161,7 +163,7 @@ public class DefaultKernelArguments implements KernelArguments, WritableKernelAr
     @Nullable
     @Override
     public Map<String, PromptExecutionSettings> getExecutionSettings() {
-        return executionSettings;
+        return Collections.unmodifiableMap(executionSettings);
     }
 
     @Override

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/orchestration/contextvariables/KernelArguments.java

@@ -49,7 +49,7 @@ public interface KernelArguments extends Buildable, Map<String, ContextVariable<
      * @return content of the variable
      */
     @Nullable
-    <T extends ContextVariable<?>> T get(String key);
+    ContextVariable<?> get(String key);
 
     /**
      * Return the variable with the given name

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/plugin/KernelParameterMetadata.java

@@ -1,6 +1,6 @@
 package com.microsoft.semantickernel.plugin;
 
-public class KernelParameterMetadata {
+public class KernelParameterMetadata<T> {
 
     /// <summary>The name of the parameter.</summary>
     private final String name;
@@ -8,18 +8,18 @@ public class KernelParameterMetadata {
     private final String description;
     private final String defaultValue;
     private final boolean isRequired;
-    private final Class<?> parameterType;
+    private final Class<T> parameterType;
 
     public KernelParameterMetadata(
         String name,
         String description,
-        Class<?> parameterType,
+        Class<T> parameterType,
         String defaultValue, boolean isRequired) {
         this.name = name;
         this.description = description;
         this.defaultValue = defaultValue;
         this.isRequired = isRequired;
-        this.parameterType = String.class;
+        this.parameterType = parameterType;
     }
 
     public String getName() {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/plugin/KernelPlugin.java

@@ -1,11 +1,10 @@
 package com.microsoft.semantickernel.plugin;
 
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-
 import com.microsoft.semantickernel.orchestration.KernelFunction;
 import com.microsoft.semantickernel.orchestration.contextvariables.CaseInsensitiveMap;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Map;
 
 public class KernelPlugin implements Iterable<KernelFunction> {
 
@@ -20,17 +19,17 @@ public class KernelPlugin implements Iterable<KernelFunction> {
         this.description = description;
         this.functions = new CaseInsensitiveMap<>();
         if (plugins != null) {
-            plugins.forEach((key,kerneFunction) -> this.functions.put(key, kerneFunction));
+            this.functions.putAll(plugins);
         }
     }
 
     public Map<String, KernelFunction> getFunctions() {
-        return functions;
+        return Collections.unmodifiableMap(functions);
     }
 
     public KernelFunction get(String functionName) {
         return functions.get(functionName);
-    }     
+    }
 
     @Override
     public Iterator<KernelFunction> iterator() {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/plugin/KernelPluginCollection.java

@@ -1,19 +1,17 @@
 package com.microsoft.semantickernel.plugin;
 
+import com.microsoft.semantickernel.orchestration.KernelFunction;
+import com.microsoft.semantickernel.orchestration.KernelFunctionMetadata;
+import com.microsoft.semantickernel.orchestration.contextvariables.CaseInsensitiveMap;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
-import javax.annotation.Nullable;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import com.microsoft.semantickernel.orchestration.KernelFunction;
-import com.microsoft.semantickernel.orchestration.KernelFunctionMetadata;
-import com.microsoft.semantickernel.orchestration.contextvariables.CaseInsensitiveMap;
-
 public class KernelPluginCollection implements Iterable<KernelPlugin> {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(KernelPluginCollection.class);
@@ -28,12 +26,10 @@ public class KernelPluginCollection implements Iterable<KernelPlugin> {
         plugins.forEach(plugin -> this.plugins.put(plugin.getName(), plugin));
     }
 
-    @Nullable
     public KernelFunction getFunction(String pluginName, String functionName) {
         KernelPlugin plugin = plugins.get(pluginName);
         if (plugin == null) {
-            LOGGER.warn("Failed to find plugin '{}'", pluginName);
-            return null;
+            throw new IllegalArgumentException("Failed to find plugin " + pluginName);
         }
         KernelFunction function = plugin.get(functionName);
 
@@ -56,6 +52,10 @@ public class KernelPluginCollection implements Iterable<KernelPlugin> {
         return plugins.values().iterator();
     }
 
+    public List<KernelPlugin> getPlugins() {
+        return new ArrayList<>(plugins.values());
+    }
+
     public void add(KernelPlugin plugin) {
         if (plugins.containsKey(plugin.getName())) {
             LOGGER.warn("Plugin {} already exists, overwriting existing plugin", plugin.getName());

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/plugin/KernelPluginFactory.java

@@ -1,6 +1,5 @@
 package com.microsoft.semantickernel.plugin;
 
-import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.microsoft.semantickernel.exceptions.SKException;
 import com.microsoft.semantickernel.orchestration.KernelFunction;
@@ -22,7 +21,6 @@ import java.nio.charset.Charset;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -219,11 +217,13 @@ public class KernelPluginFactory {
 
         return new Builder().withName(config.getName()).withDescription(config.getDescription())
             .withExecutionSettings(config.getExecutionSettings())
-            .withInputParameters(config.getInputVariables()).withPromptTemplate(promptTemplate)
-            .withPluginName(pluginDirectoryName).withTemplate(template)
+            .withInputParameters(config.getInputVariables()
+            ).withPromptTemplate(promptTemplate)
+            .withTemplate(template)
             .withTemplateFormat(config.getTemplateFormat())
             .withOutputVariable(config.getOutputVariable())
-            .withPromptTemplateFactory(promptTemplateFactory).build();
+            .withPromptTemplateFactory(promptTemplateFactory)
+            .build();
     }
 
     public static KernelPlugin importPluginFromResourcesDirectory(String parentDirectory,

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/plugin/Plugin.java

@@ -27,6 +27,6 @@ public class Plugin {
     }
 
     public List<KernelFunction> functions() {
-        return functions;
+        return Collections.unmodifiableList(functions);
     }
 }

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/semanticfunctions/AggregatorPromptTemplateFactory.java

@@ -2,12 +2,13 @@ package com.microsoft.semantickernel.semanticfunctions;
 
 import reactor.util.annotation.NonNull;
 
+import java.util.ArrayList;
 import java.util.List;
 
 public class AggregatorPromptTemplateFactory implements PromptTemplateFactory {
     private final List<PromptTemplateFactory> templateFactories;
     public AggregatorPromptTemplateFactory(List<PromptTemplateFactory> templateFactories) {
-        this.templateFactories = templateFactories;
+        this.templateFactories = new ArrayList<>(templateFactories);
     }
     @Override
     public PromptTemplate tryCreate(@NonNull PromptTemplateConfig templateConfig) {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/semanticfunctions/KernelFunctionFromMethod.java

@@ -5,6 +5,9 @@ import static com.microsoft.semantickernel.plugin.annotations.KernelFunctionPara
 import com.microsoft.semantickernel.Kernel;
 import com.microsoft.semantickernel.exceptions.AIException;
 import com.microsoft.semantickernel.exceptions.AIException.ErrorCodes;
+import com.microsoft.semantickernel.hooks.FunctionInvokedEvent;
+import com.microsoft.semantickernel.hooks.FunctionInvokingEvent;
+import com.microsoft.semantickernel.hooks.KernelHooks;
 import com.microsoft.semantickernel.orchestration.DefaultKernelFunction;
 import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.KernelFunction;
@@ -66,7 +69,21 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
         Kernel kernel,
         @Nullable KernelArguments arguments,
         ContextVariableType<T> variableType) {
-        return function.invoke(kernel, this, arguments);
+        return function.invoke(kernel, this, arguments, kernel.getHookService());
+    }
+
+    @Override
+    public <T> Mono<FunctionResult<T>> invokeAsync(
+        Kernel kernel,
+        @Nullable KernelArguments arguments,
+        @Nullable KernelHooks kernelHooks,
+        ContextVariableType<T> variableType) {
+
+        if (kernelHooks == null) {
+            kernelHooks = kernel.getHookService();
+        }
+
+        return function.invoke(kernel, this, arguments, kernelHooks);
     }
 
     public interface ImplementationFunc {
@@ -75,7 +92,8 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
             Kernel kernel,
             KernelFunction function,
             @Nullable
-            KernelArguments arguments);
+            KernelArguments arguments,
+            KernelHooks kernelHooks);
     }
 
 
@@ -138,16 +156,22 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
 
         return new ImplementationFunc() {
             @Override
-            public <T> Mono<FunctionResult<T>> invoke(Kernel kernel, KernelFunction function,
+            public <T> Mono<FunctionResult<T>> invoke(
+                Kernel kernel,
+                KernelFunction function,
                 @Nullable
-                KernelArguments arguments) {
+                KernelArguments arguments,
+                KernelHooks kernelHooks) {
 
-                //Set<Parameter> inputArgs = determineInputArgs(method);
+                FunctionInvokingEvent updatedState = kernelHooks
+                    .executeHooks(
+                        new FunctionInvokingEvent(function, arguments));
+                KernelArguments updatedArguments = updatedState.getArguments();
 
                 try {
                     List<Object> args =
                         Arrays.stream(method.getParameters())
-                            .map(getParameters(method, arguments, kernel))
+                            .map(getParameters(method, updatedArguments, kernel))
                             .collect(Collectors.toList());
 
                     Mono<?> mono;
@@ -169,7 +193,13 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
                         });
 
                     return r
-                        .map(it -> new FunctionResult<>(ContextVariable.of(it)));
+                        .map(it -> new FunctionResult<>(ContextVariable.of(it)))
+                        .map(it -> {
+                            FunctionInvokedEvent<T> updatedResult = kernelHooks
+                                .executeHooks(
+                                    new FunctionInvokedEvent<>(function, updatedArguments, it));
+                            return updatedResult.getResult();
+                        });
                 } catch (Exception e) {
                     return Mono.error(e);
                 }
@@ -232,22 +262,10 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
 
         ContextVariable<?> arg = context == null ? null : context.get(variableName);
         if (arg == null) {
-            /*
-            // If this is bound to input get the input value
-            if (inputArgs.contains(parameter)) {
-                ContextVariable<?> input = context.get(KernelArguments.MAIN_KEY);
-                if (input != null) {
-                    arg = input;
-                }
-            }
-
-             */
-
-            if (arg == null) {
-                KernelFunctionParameter annotation =
-                    parameter.getAnnotation(KernelFunctionParameter.class);
-                if (annotation != null) {
-                    // Convert from the defaultValue, which is a String to the argument type 
+            KernelFunctionParameter annotation =
+                parameter.getAnnotation(KernelFunctionParameter.class);
+            if (annotation != null) {
+                    // Convert from the defaultValue, which is a String to the argument type
                     // Expectation here is that the fromPromptString method will be able to handle a null or empty string
                     Class<?> type = annotation.type();
                     ContextVariableType<?> cvType = ContextVariableTypes.getDefaultVariableTypeForClass(type);
@@ -257,22 +275,21 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
                         arg = ContextVariable.of(value);
                     }
 
-                    if (NO_DEFAULT_VALUE.equals(arg)) {
-                        if (!annotation.required()) {
-                            return null;
-                        }
-
-                        throw new AIException(
-                            AIException.ErrorCodes.INVALID_CONFIGURATION,
-                            "Attempted to invoke function "
-                                + method.getDeclaringClass().getName()
-                                + "."
-                                + method.getName()
-                                + ". The context variable \""
-                                + variableName
-                                + "\" has not been set, and no default value is"
-                                + " specified.");
+                if (arg != null && NO_DEFAULT_VALUE.equals(arg.getValue())) {
+                    if (!annotation.required()) {
+                        return null;
                     }
+
+                    throw new AIException(
+                        AIException.ErrorCodes.INVALID_CONFIGURATION,
+                        "Attempted to invoke function "
+                            + method.getDeclaringClass().getName()
+                            + "."
+                            + method.getName()
+                            + ". The context variable \""
+                            + variableName
+                            + "\" has not been set, and no default value is"
+                            + " specified.");
                 }
             }
         }
@@ -281,7 +298,7 @@ public class KernelFunctionFromMethod extends DefaultKernelFunction {
             LOGGER.warn(formErrorMessage(method, parameter));
         }
 
-        if (NO_DEFAULT_VALUE.equals(arg)) {
+        if (arg != null && NO_DEFAULT_VALUE.equals(arg.getValue())) {
             if (parameter.getName().matches("arg\\d")) {
                 throw new AIException(
                     AIException.ErrorCodes.INVALID_CONFIGURATION,

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/semanticfunctions/KernelFunctionFromPrompt.java

@@ -8,17 +8,23 @@ import com.microsoft.semantickernel.Kernel;
 import com.microsoft.semantickernel.TextAIService;
 import com.microsoft.semantickernel.chatcompletion.AuthorRole;
 import com.microsoft.semantickernel.chatcompletion.ChatCompletionService;
+import com.microsoft.semantickernel.hooks.FunctionInvokedEvent;
+import com.microsoft.semantickernel.hooks.FunctionInvokingEvent;
+import com.microsoft.semantickernel.hooks.KernelHooks;
+import com.microsoft.semantickernel.hooks.PromptRenderedEvent;
+import com.microsoft.semantickernel.hooks.PromptRenderingEvent;
 import com.microsoft.semantickernel.orchestration.DefaultKernelFunction;
+import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.KernelFunction;
 import com.microsoft.semantickernel.orchestration.KernelFunctionMetadata;
 import com.microsoft.semantickernel.orchestration.PromptExecutionSettings;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariable;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariableType;
 import com.microsoft.semantickernel.orchestration.contextvariables.ContextVariableTypes;
-import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
 import com.microsoft.semantickernel.services.AIServiceSelection;
 import com.microsoft.semantickernel.textcompletion.TextGenerationService;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -83,23 +89,36 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
         );
     }
 
-
     private <T> Flux<FunctionResult<T>> invokeInternalAsync(
         Kernel kernel,
         @Nullable KernelArguments arguments,
+        KernelHooks kernelHooks,
         ContextVariableType<T> variableType) {
+
+        PromptRenderingEvent preRenderingHookResult = kernelHooks
+            .executeHooks(new PromptRenderingEvent(this, arguments));
+
         return this
             .template
-            .renderAsync(kernel, arguments)
+            .renderAsync(kernel, preRenderingHookResult.getArguments())
             .flatMapMany(prompt -> {
+                PromptRenderedEvent promptHookResult = kernelHooks
+                    .executeHooks(new PromptRenderedEvent(this, arguments, prompt));
+                prompt = promptHookResult.getPrompt();
+                KernelArguments args = promptHookResult.getArguments();
+
                 LOGGER.info("RENDERED PROMPT: \n{}", prompt);
 
+                FunctionInvokingEvent updateArguments = kernelHooks
+                    .executeHooks(new FunctionInvokingEvent(this, args));
+                args = updateArguments.getArguments();
+
                 AIServiceSelection aiServiceSelection = kernel
                     .getServiceSelector()
                     .trySelectAIService(
                         TextAIService.class,
                         this,
-                        arguments
+                        args
                     );
 
                 AIService client = aiServiceSelection.getService();
@@ -117,7 +136,8 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
                         .getChatMessageContentsAsync(
                             prompt,
                             executionSettings,
-                            kernel)
+                            kernel,
+                            kernelHooks)
                         .flatMapMany(Flux::fromIterable)
                         .concatMap(chatMessageContent -> {
                             if (chatMessageContent.getAuthorRole()
@@ -157,8 +177,6 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
                                 it.getMetadata()
                             );
                         });
-                    return result;
-
                 } else if (client instanceof TextGenerationService) {
                     result = ((TextGenerationService) client)
                         .getTextContentsAsync(
@@ -190,7 +208,18 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
                 } else {
                     return Flux.error(new IllegalStateException("Unknown service type"));
                 }
-                return result;
+
+                return result
+                    .map(it -> {
+                        FunctionInvokedEvent<T> updatedResult = kernelHooks
+                            .executeHooks(
+                                new FunctionInvokedEvent<>(
+                                    this,
+                                    arguments,
+                                    it));
+
+                        return updatedResult.getResult();
+                    });
             })
             .doOnError(
                 ex -> {
@@ -228,12 +257,25 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
     public <T> Mono<FunctionResult<T>> invokeAsync(
         Kernel kernel,
         @Nullable KernelArguments arguments,
+        @Nullable KernelHooks kernelHooks,
         ContextVariableType<T> variableType) {
-        return invokeInternalAsync(kernel, arguments, variableType)
+        if (kernelHooks == null) {
+            kernelHooks = kernel.getHookService();
+        }
+        return invokeInternalAsync(kernel, arguments, kernelHooks, variableType)
             .take(1)
             .single();
     }
 
+    @Override
+    public <T> Mono<FunctionResult<T>> invokeAsync(
+        Kernel kernel,
+        @Nullable KernelArguments arguments,
+        ContextVariableType<T> variableType) {
+        return invokeAsync(kernel, arguments, null, variableType);
+    }
+
+
     /*
      * Given a json string, invoke the tool specified in the json string.
      * At this time, the only tool we have is 'function'.
@@ -327,12 +369,11 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
 
         private PromptTemplate promptTemplate;
         private String name;
-        private String pluginName;
         private Map<String, PromptExecutionSettings> executionSettings;
         private String description;
         private List<InputVariable> inputVariables;
         private String template;
-        private String templateFormat;
+        private String templateFormat = PromptTemplateConfig.SEMANTIC_KERNEL_TEMPLATE_FORMAT;
         private OutputVariable outputVariable;
         private PromptTemplateFactory promptTemplateFactory;
 
@@ -345,7 +386,7 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
 
         @Override
         public FromPromptBuilder withInputParameters(List<InputVariable> inputVariables) {
-            this.inputVariables = inputVariables;
+            this.inputVariables = new ArrayList<>(inputVariables);
             return this;
         }
 
@@ -355,12 +396,6 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
             return this;
         }
 
-        @Override
-        public FromPromptBuilder withPluginName(String name) {
-            this.pluginName = name;
-            return this;
-        }
-
         @Override
         public FromPromptBuilder withExecutionSettings(
             Map<String, PromptExecutionSettings> executionSettings) {
@@ -381,7 +416,8 @@ public class KernelFunctionFromPrompt extends DefaultKernelFunction {
                 this.executionSettings = new HashMap<>();
             }
 
-            this.executionSettings.put("default", executionSettings);
+            this.executionSettings.put(PromptExecutionSettings.DEFAULT_SERVICE_ID,
+                executionSettings);
 
             if (executionSettings.getServiceId() != null) {
                 this.executionSettings.put(executionSettings.getServiceId(), executionSettings);

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/semanticfunctions/KernelPromptTemplateFactory.java

@@ -5,15 +5,12 @@ import static com.microsoft.semantickernel.semanticfunctions.PromptTemplateConfi
 
 import com.microsoft.semantickernel.templateengine.handlebars.HandlebarsPromptTemplate;
 import com.microsoft.semantickernel.templateengine.semantickernel.DefaultPromptTemplate;
+import javax.annotation.Nonnull;
 import java.util.Locale;
 
 public class KernelPromptTemplateFactory implements PromptTemplateFactory {
 
-    public PromptTemplate tryCreate(PromptTemplateConfig templateConfig) {
-        if (templateConfig == null || templateConfig.getTemplateFormat() == null) {
-            return new DefaultPromptTemplate(templateConfig);
-        }
-
+    public PromptTemplate tryCreate(@Nonnull PromptTemplateConfig templateConfig) {
         switch (templateConfig.getTemplateFormat().toLowerCase(Locale.ROOT)) {
             case SEMANTIC_KERNEL_TEMPLATE_FORMAT:
                 return new DefaultPromptTemplate(templateConfig);

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/semanticfunctions/PromptTemplateConfig.java

@@ -16,11 +16,13 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
+import javax.annotation.Nullable;
 
 @JsonIgnoreProperties(ignoreUnknown = true)
 public class PromptTemplateConfig {
 
     public static final int CURRENT_SCHEMA = 1;
+    public static final String DEFAULT_CONFIG_NAME = "default";
     private String name;
 
     private String template;
@@ -40,7 +42,7 @@ public class PromptTemplateConfig {
     public PromptTemplateConfig(String template) {
         this(
             CURRENT_SCHEMA,
-            "default",
+            DEFAULT_CONFIG_NAME,
             template,
             SEMANTIC_KERNEL_TEMPLATE_FORMAT,
             "",
@@ -58,7 +60,10 @@ public class PromptTemplateConfig {
         String name,
         @JsonProperty("template")
         String template,
-        @JsonProperty("template_format")
+        @Nullable
+        @JsonProperty(
+            value = "template_format",
+            defaultValue = SEMANTIC_KERNEL_TEMPLATE_FORMAT)
         String templateFormat,
         @JsonProperty("description")
         String description,
@@ -70,6 +75,9 @@ public class PromptTemplateConfig {
         Map<String, PromptExecutionSettings> executionSettings) {
         this.name = name;
         this.template = template;
+        if (templateFormat == null) {
+            templateFormat = SEMANTIC_KERNEL_TEMPLATE_FORMAT;
+        }
         this.templateFormat = templateFormat;
         this.description = description;
         if (inputVariables == null) {
@@ -78,7 +86,11 @@ public class PromptTemplateConfig {
             this.inputVariables = new ArrayList<>(inputVariables);
         }
         this.outputVariable = outputVariable;
-        this.executionSettings = executionSettings;
+        if (executionSettings == null) {
+            this.executionSettings = new HashMap<>();
+        } else {
+            this.executionSettings = new HashMap<>(executionSettings);
+        }
     }
 
     /**
@@ -107,6 +119,18 @@ public class PromptTemplateConfig {
         );
     }
 
+    public PromptTemplateConfig(PromptTemplateConfig promptTemplate) {
+        this(
+            promptTemplate.name,
+            promptTemplate.template,
+            promptTemplate.templateFormat,
+            promptTemplate.description,
+            promptTemplate.inputVariables,
+            promptTemplate.outputVariable,
+            promptTemplate.executionSettings
+        );
+    }
+
     public List<KernelParameterMetadata> getKernelParametersMetadata() {
         if (inputVariables == null) {
             return Collections.emptyList();
@@ -134,98 +158,16 @@ public class PromptTemplateConfig {
     }
 
     public void addInputVariable(InputVariable inputVariable) {
-        if (inputVariables == null) {
-            inputVariables = new ArrayList<>();
-        }
         inputVariables.add(inputVariable);
     }
 
-
-    public static class ExecutionSettingsModel {
-
-        @JsonProperty("model_id")
-        private String modelId;
-
-        @JsonProperty("model_id_pattern")
-        private String modelIdPattern;
-
-        @JsonProperty("service_id")
-        private String serviceId;
-
-        @JsonProperty("temperature")
-        private String temperature;
-
-        @JsonProperty("additional_properties")
-        private final Map<String, Object> additionalProperties;
-
-        public Object get(String propertyName) {
-            return additionalProperties.get(propertyName);
-        }
-
-        public void set(String propertyName, Object value) {
-            additionalProperties.put(propertyName, value);
-        }
-
-        public ExecutionSettingsModel() {
-            this.additionalProperties = new HashMap<>();
-        }
-
-        public ExecutionSettingsModel(
-            String modelId,
-            String modelIdPattern,
-            String serviceId,
-            String temperature,
-            Map<String, Object> additionalProperties) {
-            this.modelId = modelId;
-            this.modelIdPattern = modelIdPattern;
-            this.serviceId = serviceId;
-            this.temperature = temperature;
-            this.additionalProperties = additionalProperties;
-        }
-
-        public String getModelId() {
-            return modelId;
-        }
-
-        public void setModelId(String modelId) {
-            this.modelId = modelId;
-        }
-
-        public String getModelIdPattern() {
-            return modelIdPattern;
-        }
-
-        public void setModelIdPattern(String modelIdPattern) {
-            this.modelIdPattern = modelIdPattern;
-        }
-
-        public String getServiceId() {
-            return serviceId;
-        }
-
-        public void setServiceId(String serviceId) {
-            this.serviceId = serviceId;
-        }
-
-        public String getTemperature() {
-            return temperature;
-        }
-
-        public void setTemperature(String temperature) {
-            this.temperature = temperature;
-        }
-
-        public Map<String, Object> getAdditionalProperties() {
-            return additionalProperties;
-        }
-    }
-
     public String getName() {
         return name;
     }
 
-    public void setName(String name) {
+    public PromptTemplateConfig setName(String name) {
         this.name = name;
+        return this;
     }
 
     public String getTemplate() {
@@ -253,11 +195,11 @@ public class PromptTemplateConfig {
     }
 
     public List<InputVariable> getInputVariables() {
-        return inputVariables;
+        return Collections.unmodifiableList(inputVariables);
     }
 
     public void setInputVariables(List<InputVariable> inputVariables) {
-        this.inputVariables = inputVariables;
+        this.inputVariables = new ArrayList<>(inputVariables);
     }
 
     public OutputVariable getOutputVariable() {
@@ -269,11 +211,12 @@ public class PromptTemplateConfig {
     }
 
     public Map<String, PromptExecutionSettings> getExecutionSettings() {
-        return executionSettings;
+        return Collections.unmodifiableMap(executionSettings);
     }
 
+
     public void setExecutionSettings(Map<String, PromptExecutionSettings> executionSettings) {
-        this.executionSettings = executionSettings;
+        this.executionSettings = new HashMap<>(executionSettings);
     }
 
     public static PromptTemplateConfig parseFromJson(String json) throws SKException {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/services/AIServiceSelection.java

@@ -7,32 +7,37 @@ import com.microsoft.semantickernel.orchestration.PromptExecutionSettings;
 /**
  * The result of an AI service selection.
  */
-public class AIServiceSelection {
+public class AIServiceSelection<T extends AIService> {
 
-    private final AIService service;
+    private final T service;
     private final PromptExecutionSettings settings;
 
     /**
      * Creates a new AI service selection.
-     * @param service The selected AI service.
-     * @param settings The settings associated with the selected service. This may be null even if a service is selected..
+     *
+     * @param service  The selected AI service.
+     * @param settings The settings associated with the selected service. This may be null even if a
+     *                 service is selected..
      */
-    public AIServiceSelection(AIService service, PromptExecutionSettings settings) {
+    public AIServiceSelection(T service, PromptExecutionSettings settings) {
         this.service = service;
         this.settings = settings;
     }
 
     /**
      * Gets the selected AI service.
+     *
      * @return The selected AI service.
      */
-    public AIService getService() {
+    public T getService() {
         return service;
     }
 
     /**
      * Gets the settings associated with the selected service.
-     * @return The settings associated with the selected service. This may be null even if a service is selected.
+     *
+     * @return The settings associated with the selected service. This may be null even if a service
+     * is selected.
      */
     public PromptExecutionSettings getSettings() {
         return settings;

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/services/AIServiceSelector.java

@@ -26,8 +26,8 @@ public interface AIServiceSelector {
      * @return
      */
     @Nullable
-    AIServiceSelection trySelectAIService(
-        Class<? extends AIService> serviceType,
+    <T extends AIService> AIServiceSelection<T> trySelectAIService(
+        Class<T> serviceType,
         @Nullable
         KernelFunction function,
 

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/services/BaseAIServiceSelector.java

@@ -20,20 +20,20 @@ public abstract class BaseAIServiceSelector implements AIServiceSelector {
 
     @Override
     @Nullable
-    public AIServiceSelection trySelectAIService(
-        Class<? extends AIService> serviceType,
-
+    public <T extends AIService> AIServiceSelection<T> trySelectAIService(
+        Class<T> serviceType,
         @Nullable
         KernelFunction function,
 
         @Nullable
-        KernelArguments arguments) {
+        KernelArguments arguments
+    ) {
         return trySelectAIService(serviceType, function, arguments, services);
     }
 
     @Nullable
-    public abstract AIServiceSelection trySelectAIService(
-        Class<? extends AIService> serviceType,
+    public abstract <T extends AIService> AIServiceSelection<T> trySelectAIService(
+        Class<T> serviceType,
 
         @Nullable
         KernelFunction function,

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/services/OrderedAIServiceSelector.java

@@ -29,8 +29,8 @@ public class OrderedAIServiceSelector extends BaseAIServiceSelector {
     }
 
     @Nullable
-    public AIServiceSelection trySelectAIService(
-        Class<? extends AIService> serviceType,
+    public <T extends AIService> AIServiceSelection<T> trySelectAIService(
+        Class<T> serviceType,
         @Nullable
         KernelFunction function,
         @Nullable
@@ -108,10 +108,9 @@ public class OrderedAIServiceSelector extends BaseAIServiceSelector {
         PromptExecutionSettings settings;
 
         if (executionSettings.containsKey(PromptExecutionSettings.DEFAULT_SERVICE_ID)) {
-            executionSettings.get(PromptExecutionSettings.DEFAULT_SERVICE_ID);
             settings = executionSettings.get(PromptExecutionSettings.DEFAULT_SERVICE_ID);
         } else {
-            settings = executionSettings.values().stream().findFirst().orElseGet(null);
+            settings = executionSettings.values().stream().findFirst().orElseGet(() -> null);
         }
 
         if (service != null) {

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/templateengine/handlebars/HandlebarsPromptTemplate.java

@@ -1,21 +1,9 @@
 // Copyright (c) Microsoft. All rights reserved.
 package com.microsoft.semantickernel.templateengine.handlebars;
 
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map.Entry;
-import java.util.Optional;
-import java.util.Set;
-
-import javax.annotation.Nullable;
-
 import com.github.jknack.handlebars.Context;
 import com.github.jknack.handlebars.Handlebars;
+import com.github.jknack.handlebars.Options;
 import com.github.jknack.handlebars.ValueResolver;
 import com.microsoft.semantickernel.Kernel;
 import com.microsoft.semantickernel.chatcompletion.ChatHistory;
@@ -28,21 +16,28 @@ import com.microsoft.semantickernel.plugin.KernelPlugin;
 import com.microsoft.semantickernel.plugin.KernelPluginCollection;
 import com.microsoft.semantickernel.semanticfunctions.PromptTemplate;
 import com.microsoft.semantickernel.semanticfunctions.PromptTemplateConfig;
-
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map.Entry;
+import java.util.Optional;
+import java.util.Set;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import reactor.core.publisher.Mono;
 
 public class HandlebarsPromptTemplate implements PromptTemplate {
 
-    @Nullable
-    private PromptTemplateConfig promptTemplate;
-
-    public HandlebarsPromptTemplate() {
-        this(null);
-    }
+    private final PromptTemplateConfig promptTemplate;
 
     public HandlebarsPromptTemplate(
-        @Nullable PromptTemplateConfig promptTemplate) {
-        this.promptTemplate = promptTemplate;
+        @Nonnull PromptTemplateConfig promptTemplate) {
+        this.promptTemplate = new PromptTemplateConfig(promptTemplate);
     }
 
 
@@ -93,7 +88,7 @@ public class HandlebarsPromptTemplate implements PromptTemplate {
 
         @Override
         public Object resolve(Object context, String name) {
-            if (context instanceof KernelPluginCollection) {    
+            if (context instanceof KernelPluginCollection) {
                 return context;
             }
             if (context instanceof KernelFunction) {
@@ -109,7 +104,7 @@ public class HandlebarsPromptTemplate implements PromptTemplate {
 
         @Override
         public Object resolve(Object context) {
-            if (context instanceof KernelPluginCollection) {    
+            if (context instanceof KernelPluginCollection) {
                 return ((KernelPluginCollection) context).iterator();
             }
             return UNRESOLVED;
@@ -163,98 +158,99 @@ public class HandlebarsPromptTemplate implements PromptTemplate {
         private final String template;
         private final Handlebars handlebars;
 
+
+        @SuppressFBWarnings("CT_CONSTRUCTOR_THROW")// Think this is a false positive
         public HandleBarsPromptTemplateHandler(Kernel kernel, String template) {
             this.kernel = kernel;
             this.template = template;
             this.handlebars = new Handlebars();
-            this.handlebars.registerHelper(
-                "message",
-                (context, options) -> {
-                        String role = options.hash("role");
-                        String content = (String) options.fn(context);
+            this.handlebars
+                .registerHelper("message", HandleBarsPromptTemplateHandler::handleMessage)
+                .registerHelper("each", HandleBarsPromptTemplateHandler::handleEach)
+                .registerHelper("functions", (context, options) -> handleFunctions(kernel, options))
+                .registerHelper("function",
+                    (context, options) -> handleFunction((KernelFunction) context));
+            // TODO: 1.0 Add more helpers
+        }
 
-                        if (context instanceof Optional) {
-                            ChatMessageContent message = ((Optional<ChatMessageContent>) context).orElse(null);
-                            if (message != null) {
-                                if (role == null || role.isEmpty()) {
-                                    role = message.getAuthorRole().name();
-                                }
-                                content = message.getContent();
-                            }
-                        }
+        private static Handlebars.SafeString handleFunction(KernelFunction context) {
+            KernelFunction function = context;
+            String pluginName = function.getSkillName();
+            String functionName = function.getName();
+            String description = function.getDescription();
+            StringBuilder sb = new StringBuilder(
+                String.format(
+                    "<function pluginName=\"%s\" name=\"%s\" description=\"%s\">",
+                    pluginName, functionName, description));
+            List<KernelParameterMetadata> parameters = function.getMetadata().getParameters();
+            parameters.forEach(p -> {
+                sb.append(String.format(
+                    "<parameter name=\"%s\" description=\"%s\" defaultValue=\"%s\" isRequired=\"%s\" type=\"%s\"/>",
+                    p.getName(), p.getDescription(), p.getDefaultValue(), p.isRequired(),
+                    p.getType()));
+            });
+            sb.append("</function>");
+            return new Handlebars.SafeString(sb.toString());
+        }
 
-                        if (role != null && !role.isEmpty()) {
-                            return new Handlebars.SafeString(
-                                String.format(
-                                    "<message role=\"%s\">%s</message>",
-                                    role.toLowerCase(Locale.ROOT), content));
-                        }
-                        return "";
+        private static Handlebars.SafeString handleFunctions(Kernel kernel, Options options)
+            throws IOException {
+            StringBuilder sb = new StringBuilder("<functions>");
+            KernelPluginCollection plugins = kernel.getPlugins();
+            sb.append(options.fn(plugins));
+            sb.append("</functions>");
+
+            return new Handlebars.SafeString(sb.toString());
+        }
+
+        private static CharSequence handleEach(Object context, Options options)
+            throws IOException {
+            if (context instanceof ChatHistory) {
+                StringBuilder sb = new StringBuilder("<messages>");
+                for (ChatMessageContent message : (ChatHistory) context) {
+                    sb.append(options.fn(message));
+                }
+                sb.append("</messages>");
+                return new Handlebars.SafeString(sb.toString());
+            }
+            if (context instanceof KernelPluginCollection) {
+                StringBuilder sb = new StringBuilder();
+                Iterator<KernelPlugin> plugins = ((KernelPluginCollection) context).iterator();
+                while (plugins.hasNext()) {
+                    KernelPlugin plugin = plugins.next();
+                    Iterator<KernelFunction> functions = plugin.iterator();
+                    while (functions.hasNext()) {
+                        KernelFunction function = functions.next();
+                        sb.append(options.fn(function));
                     }
-                )
+                }
+                return new Handlebars.SafeString(sb.toString());
+            }
+            return "";
+        }
 
-                .registerHelper(
-                "each",
-                    (context, options) -> {
-                        if (context instanceof ChatHistory) {
-                            StringBuilder sb = new StringBuilder("<messages>");
-                            for(ChatMessageContent message : (ChatHistory) context) {
-                                sb.append(options.fn(message));
-                            }
-                            sb.append("</messages>");
-                            return new Handlebars.SafeString(sb.toString());
-                        }
-                        if (context instanceof KernelPluginCollection) {
-                            StringBuilder sb = new StringBuilder();
-                            Iterator<KernelPlugin> plugins = ((KernelPluginCollection) context).iterator();
-                            while (plugins.hasNext()) {
-                                KernelPlugin plugin = plugins.next();
-                                Iterator<KernelFunction> functions = plugin.iterator();
-                                while (functions.hasNext()) {
-                                    KernelFunction function = functions.next();
-                                    sb.append(options.fn(function));
-                                }
-                            }
-                            return new Handlebars.SafeString(sb.toString());
-                        }
-                        return "";
-                    }
-                )
+        private static CharSequence handleMessage(Object context, Options options)
+            throws IOException {
+            String role = options.hash("role");
+            String content = (String) options.fn(context);
 
-                .registerHelper(
-                "functions",
-                    (context, options) -> {
-                        StringBuilder sb = new StringBuilder("<functions>");
-                        KernelPluginCollection plugins = kernel.getPlugins();
-                        sb.append(options.fn(plugins));
-                        sb.append("</functions>");
-                        
-                        return new Handlebars.SafeString(sb.toString());
+            if (context instanceof Optional) {
+                ChatMessageContent message = ((Optional<ChatMessageContent>) context).orElse(null);
+                if (message != null) {
+                    if (role == null || role.isEmpty()) {
+                        role = message.getAuthorRole().name();
                     }
-                )
+                    content = message.getContent();
+                }
+            }
 
-                .registerHelper(
-                "function",
-                    (context, options) -> {
-                        KernelFunction function = (KernelFunction) context;
-                        String pluginName = function.getSkillName();
-                        String functionName = function.getName();
-                        String description = function.getDescription();
-                        StringBuilder sb = new StringBuilder(
-                            String.format(
-                                "<function pluginName=\"%s\" name=\"%s\" description=\"%s\">",
-                                pluginName, functionName, description));
-                        List<KernelParameterMetadata> parameters = function.getMetadata().getParameters();
-                        parameters.forEach(p -> {
-                            sb.append(String.format(
-                                "<parameter name=\"%s\" description=\"%s\" defaultValue=\"%s\" isRequired=\"%s\" type=\"%s\"/>",
-                                p.getName(), p.getDescription(), p.getDefaultValue(), p.isRequired(), p.getType()));
-                        });
-                        sb.append("</function>");
-                        return new Handlebars.SafeString(sb.toString());
-                    }
-                );
-                // TODO: 1.0 Add more helpers
+            if (role != null && !role.isEmpty()) {
+                return new Handlebars.SafeString(
+                    String.format(
+                        "<message role=\"%s\">%s</message>",
+                        role.toLowerCase(Locale.ROOT), content));
+            }
+            return "";
         }
 
 

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/templateengine/semantickernel/DefaultPromptTemplate.java

@@ -19,6 +19,7 @@ import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -28,16 +29,11 @@ import reactor.core.publisher.Mono;
 /// </summary>
 public class DefaultPromptTemplate implements PromptTemplate {
 
-    @Nullable
-    private PromptTemplateConfig promptTemplate;
-
-    public DefaultPromptTemplate() {
-        this(null);
-    }
+    private final PromptTemplateConfig promptTemplate;
 
     public DefaultPromptTemplate(
-        @Nullable PromptTemplateConfig promptTemplate) {
-        this.promptTemplate = promptTemplate;
+        @Nonnull PromptTemplateConfig promptTemplate) {
+        this.promptTemplate = new PromptTemplateConfig(promptTemplate);
     }
 
     /// <summary>

java/semantickernel-api/src/main/java/com/microsoft/semantickernel/templateengine/semantickernel/blocks/CodeBlock.java

@@ -11,6 +11,7 @@ import com.microsoft.semantickernel.orchestration.contextvariables.DefaultKernel
 import com.microsoft.semantickernel.orchestration.FunctionResult;
 import com.microsoft.semantickernel.orchestration.contextvariables.KernelArguments;
 import com.microsoft.semantickernel.templateengine.semantickernel.TemplateException;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -123,7 +124,9 @@ public final class CodeBlock extends Block implements CodeRendering {
             arguments = this.enrichFunctionArguments(kernel, fBlock,
                 arguments ==
                     null ? new DefaultKernelArguments()
-                    : new DefaultKernelArguments(arguments, new HashMap<>()));
+                    : new DefaultKernelArguments(
+                        arguments,
+                        new HashMap<>()));
         }
 
         return kernel

java/spotbugs-exclude.xml

@@ -1,119 +1,4 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <FindBugsFilter>
 
-  <!-- NullMemory.getInstance() may expose internal representation by returning NullMemory.DEFAULT, but NullMemory has no internal representation. -->
-  <Match>
-    <Class name="com.microsoft.semantickernel.memory.NullMemory"/>
-    <Method name="getInstance"/>
-    <Bug pattern="MS_EXPOSE_REP"/>
-  </Match>
-
-  <!-- DefaultSemanticTextMemory(MemoryStore, EmbeddingGeneration) may expose internal representation by storing an externally mutable object into DefaultSemanticTextMemory._storage  -->
-  <!-- TODO: This should be a temporary exclusion pending a proper fix, if possible. -->
-  <Match>
-    <Class name="com.microsoft.semantickernel.memory.DefaultSemanticTextMemory"/>
-    <Field name="_storage"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-  
-  <Match>
-    <Class name="com.microsoft.semantickernel.Kernel$Builder"/>
-    <Method name="withMemoryStore"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.Kernel$Builder"/>
-    <Method name="withMemory"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.DefaultKernel"/>
-    <Field name="memoryStore"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.DefaultKernel"/>
-    <Method name="getMemory"/>
-    <Bug pattern="EI_EXPOSE_REP"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.DefaultKernel"/>
-    <Field name="memory"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.DefaultKernel"/>
-    <Method name="registerMemory"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.ai.embeddings.Embedding"/>
-    <Method name="getVector"/>
-    <Bug pattern="EI_EXPOSE_REP"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.memory.DefaultSemanticTextMemory$Builder"/>
-    <Method name="withStorage"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.skilldefinition.DefaultSkillCollection"/>
-    <Method name="getSkillCollection"/>
-    <Bug pattern="EI_EXPOSE_REP"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.jdbc.JDBCConnector"/>
-    <Method name="&lt;init&gt;"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.jdbc.JDBCMemoryStore"/>
-    <Method name="&lt;init&gt;"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.jdbc.JDBCMemoryStore$Builder"/>
-    <Method name="withConnection"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.sqlite.SQLiteMemoryStore$Builder"/>
-    <Method name="withConnection"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.postgresql.PostgreSQLMemoryStore$Builder"/>
-    <Method name="withConnection"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.mysql.MySQLMemoryStore$Builder"/>
-    <Method name="withConnection"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.azurecognitivesearch.AzureCognitiveSearchMemoryRecord"/>
-    <Bug pattern="EI_EXPOSE_REP"/>
-  </Match>
-  
-  <Match>
-    <Class name="com.microsoft.semantickernel.connectors.memory.azurecognitivesearch.AzureCognitiveSearchMemoryStore"/>
-    <Bug pattern="EI_EXPOSE_REP2"/>
-  </Match>
-
 </FindBugsFilter>