Java: Fix importing multiple plugin functions (#5679)

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### Contribution Checklist

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- [ ] 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)
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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/api-test/integration-tests/src/test/java/com/microsoft/semantickernel/tests/ImportingMultiplePluginsTest.java

@@ -0,0 +1,51 @@
+// Copyright (c) Microsoft. All rights reserved.
+package com.microsoft.semantickernel.tests;
+
+import com.microsoft.semantickernel.Kernel;
+import com.microsoft.semantickernel.plugin.KernelPlugin;
+import com.microsoft.semantickernel.plugin.KernelPluginFactory;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ImportingMultiplePluginsTest {
+
+    @Test
+    public void canImportMultiplePlugins() {
+        KernelPlugin summarize = KernelPluginFactory.importPluginFromResourcesDirectory(
+            "Plugins",
+            "SummarizePlugin",
+            "Summarize",
+            null,
+            String.class);
+
+        KernelPlugin topics = KernelPluginFactory.importPluginFromResourcesDirectory(
+            "Plugins",
+            "SummarizePlugin",
+            "Topics",
+            null,
+            String.class);
+
+        KernelPlugin notegen = KernelPluginFactory.importPluginFromResourcesDirectory(
+            "Plugins",
+            "SummarizePlugin",
+            "Notegen",
+            null,
+            String.class);
+
+        Kernel kernel = Kernel.builder()
+            .withPlugin(summarize)
+            .withPlugin(topics)
+            .withPlugin(notegen)
+            .build();
+
+        Assertions.assertEquals(3,
+            kernel.getPlugin("SummarizePlugin").getFunctions().size());
+        Assertions.assertEquals("Summarize",
+            kernel.getPlugin("SummarizePlugin").get("Summarize").getName());
+        Assertions.assertEquals("Topics",
+            kernel.getPlugin("SummarizePlugin").get("Topics").getName());
+        Assertions.assertEquals("Notegen",
+            kernel.getPlugin("SummarizePlugin").get("Notegen").getName());
+
+    }
+}

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

@@ -36,7 +36,17 @@ class KernelPluginCollection {
      * plugins.
      */
     KernelPluginCollection(List<KernelPlugin> plugins) {
-        plugins.forEach(plugin -> this.plugins.put(plugin.getName(), plugin));
+        plugins.forEach(plugin -> putOrMerge(plugin.getName(), plugin));
+    }
+
+    private void putOrMerge(String pluginName, KernelPlugin plugin) {
+        if (plugins.containsKey(pluginName)) {
+            plugin.getFunctions()
+                .entrySet()
+                .forEach(entry -> plugins.get(pluginName).addFunction(entry.getValue()));
+        } else {
+            plugins.put(pluginName, plugin);
+        }
     }
 
     /**

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

@@ -322,7 +322,8 @@ public class KernelPluginFactory {
                     // configuration, unable to parse {configPath}");
                 }
 
-                KernelFunction<?> plugin = getKernelFunction(promptTemplateFactory, configPath,
+                KernelFunction<?> plugin = getKernelFunction(dir.getName(), promptTemplateFactory,
+                    configPath,
                     promptPath);
 
                 plugins.put(dir.getName(), plugin);
@@ -338,6 +339,7 @@ public class KernelPluginFactory {
     }
 
     private static KernelFunction<?> getKernelFunction(
+        @Nullable String functionName,
         @Nullable PromptTemplateFactory promptTemplateFactory,
         File configPath,
         File promptPath)
@@ -350,7 +352,7 @@ public class KernelPluginFactory {
             String template = new String(Files.readAllBytes(promptPath.toPath()),
                 Charset.defaultCharset());
 
-            return getKernelFunction(promptTemplateFactory, config, template);
+            return getKernelFunction(functionName, promptTemplateFactory, config, template);
         } catch (Exception e) {
             LOGGER.error("Failed to read file " + configPath.getAbsolutePath(), e);
 
@@ -360,6 +362,7 @@ public class KernelPluginFactory {
 
     @SuppressWarnings("unchecked")
     private static <T> KernelFunction<T> getKernelFunction(
+        @Nullable String functionName,
         @Nullable PromptTemplateFactory promptTemplateFactory,
         PromptTemplateConfig config,
         String template) {
@@ -373,8 +376,12 @@ public class KernelPluginFactory {
             promptTemplate = new KernelPromptTemplateFactory().tryCreate(config);
         }
 
+        if (config.getName() != null) {
+            functionName = config.getName();
+        }
+
         return (KernelFunction<T>) new KernelFunctionFromPrompt.Builder<>()
-            .withName(config.getName())
+            .withName(functionName)
             .withDescription(config.getDescription())
             .withExecutionSettings(config.getExecutionSettings())
             .withInputParameters(config.getInputVariables())
@@ -439,7 +446,7 @@ public class KernelPluginFactory {
                 + pluginDirectoryName);
             return null;
         }
-        KernelFunction<?> function = getKernelFunction(promptTemplateFactory,
+        KernelFunction<?> function = getKernelFunction(functionName, promptTemplateFactory,
             promptTemplateConfig, template);
 
         HashMap<String, KernelFunction<?>> plugins = new HashMap<>();