Java: Http skill Added (#1712)

Added HttpSkill for Java

### Motivation and Context
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Based on the
[http_skill.py](https://github.com/microsoft/semantic-kernel/blob/main/python/semantic_kernel/core_skills/http_skill.py)

I implemented the Http Skill by using Mono of Project Reactor.
And I implemented the Test code with Mock.

### Description
<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->


### Contribution Checklist
<!-- Before submitting this PR, please make sure: -->
- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows SK Contribution Guidelines
(https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
- [ ] The code follows the .NET coding conventions
(https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions)
verified with `dotnet format`
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

java/semantickernel-core-skills/pom.xml

@@ -35,5 +35,4 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
-
 </project>

java/semantickernel-core-skills/src/main/java/com/microsoft/semantickernel/coreskills/HttpSkill.java

@@ -0,0 +1,99 @@
+// Copyright (c) Microsoft. All rights reserved.
+package com.microsoft.semantickernel.coreskills;
+
+import com.azure.core.http.HttpClient;
+import com.azure.core.http.HttpMethod;
+import com.azure.core.http.HttpRequest;
+import com.azure.core.http.HttpResponse;
+
+import reactor.core.publisher.Mono;
+
+/**
+ * A skill that provides HTTP functionality.
+ *
+ * <p>Usage:
+ *
+ * <p>Usage: kernel.importSkill(new HttpSkill(), "http");
+ *
+ * <p>Examples:
+ *
+ * <p>{{http.getAsync $url}}
+ *
+ * <p>{{http.postAsync $url}}
+ *
+ * <p>{{http.putAsync $url}}
+ *
+ * <p>{{http.deleteAsync $url}}
+ */
+public class HttpSkill {
+
+    private final HttpClient httpClient;
+
+    public HttpSkill() {
+        this.httpClient = HttpClient.createDefault();
+    }
+
+    public HttpSkill(HttpClient httpClient) {
+        this.httpClient = httpClient;
+    }
+
+    /**
+     * Sends an HTTP GET request to the specified URI and returns body as a string.
+     *
+     * @param url The URI to send the request to.
+     * @return The response body as a string.
+     */
+    public Mono<String> getAsync(String url) {
+        if (url == null || url.isEmpty()) {
+            return Mono.error(new IllegalArgumentException("url cannot be `null` or empty"));
+        }
+        HttpRequest request = new HttpRequest(HttpMethod.GET, url);
+        return httpClient.send(request).flatMap(response -> response.getBodyAsString());
+    }
+
+    /**
+     * Sends an HTTP POST request to the specified URI and returns body as a string.
+     *
+     * @param url The URI to send the request to.
+     * @param body The response body as a string.
+     * @return
+     */
+    public Mono<String> postAsync(String url, String body) {
+        if (url == null || url.isEmpty()) {
+            return Mono.error(new IllegalArgumentException("url cannot be `null` or empty"));
+        }
+        HttpRequest request = new HttpRequest(HttpMethod.POST, url);
+        request.setBody(body);
+        return httpClient.send(request).flatMap(response -> response.getBodyAsString());
+    }
+
+    /**
+     * Sends an HTTP PUT request to the specified URI and returns body as a string.
+     *
+     * @param url The URI to send the request to.
+     * @param body The response body as a string.
+     * @return
+     */
+    public Mono<String> putAsync(String url, String body) {
+        if (url == null || url.isEmpty()) {
+            return Mono.error(new IllegalArgumentException("url cannot be `null` or empty"));
+        }
+        HttpRequest request = new HttpRequest(HttpMethod.PUT, url);
+        request.setBody(body);
+        return httpClient.send(request).flatMap(response -> response.getBodyAsString());
+    }
+
+    /**
+     * Sends an HTTP DELETE request to the specified URI and returns body as a string.
+     *
+     * @param url The URI to send the request to.
+     * @return The response body as a string.
+     */
+    public Mono<HttpResponse> deleteAsync(String url) {
+        if (url == null || url.isEmpty()) {
+            return Mono.error(new IllegalArgumentException("url cannot be `null` or empty"));
+        }
+        HttpRequest request = new HttpRequest(HttpMethod.DELETE, url);
+        return httpClient.send(request).flatMap(response -> Mono.just(response));
+    }
+}

java/semantickernel-core-skills/src/test/java/com/microsoft/semantickernel/coreskills/HttpSkillTest.java

@@ -0,0 +1,72 @@
+// Copyright (c) Microsoft. All rights reserved.
+package com.microsoft.semantickernel.coreskills;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.when;
+
+import com.azure.core.http.HttpClient;
+import com.azure.core.http.HttpRequest;
+import com.azure.core.http.HttpResponse;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+public class HttpSkillTest {
+
+    private HttpSkill httpSkill;
+
+    @Mock private HttpClient httpClient;
+
+    @Mock private HttpResponse httpResponse;
+
+    @BeforeEach
+    public void setUp() {
+        MockitoAnnotations.openMocks(this);
+        httpSkill = new HttpSkill(httpClient);
+    }
+
+    @Test
+    public void testGetAsync() {
+        String url = "https://example.com";
+        String responseBody = "Response body";
+        when(httpResponse.getBodyAsString()).thenReturn(Mono.just(responseBody));
+        when(httpClient.send(any(HttpRequest.class))).thenReturn(Mono.just(httpResponse));
+        Mono<String> responseMono = httpSkill.getAsync(url);
+        StepVerifier.create(responseMono).expectNext(responseBody).verifyComplete();
+    }
+
+    @Test
+    public void testPostAsync() {
+        String url = "https://example.com";
+        String body = "{\"key\": \"value\"}";
+        String responseBody = "Response body";
+        when(httpResponse.getBodyAsString()).thenReturn(Mono.just(responseBody));
+        when(httpClient.send(any(HttpRequest.class))).thenReturn(Mono.just(httpResponse));
+        Mono<String> responseMono = httpSkill.postAsync(url, body);
+        StepVerifier.create(responseMono).expectNext(responseBody).verifyComplete();
+    }
+
+    @Test
+    public void testPutAsync() {
+        String url = "https://example.com";
+        String body = "{\"key\": \"value\"}";
+        String responseBody = "Response body";
+        when(httpResponse.getBodyAsString()).thenReturn(Mono.just(responseBody));
+        when(httpClient.send(any(HttpRequest.class))).thenReturn(Mono.just(httpResponse));
+        Mono<String> responseMono = httpSkill.putAsync(url, body);
+        StepVerifier.create(responseMono).expectNext(responseBody).verifyComplete();
+    }
+
+    @Test
+    public void testDeleteAsync() {
+        String url = "https://example.com";
+        when(httpClient.send(any(HttpRequest.class))).thenReturn(Mono.just(httpResponse));
+        Mono<HttpResponse> responseMono = httpSkill.deleteAsync(url);
+        StepVerifier.create(responseMono).expectNext(httpResponse).verifyComplete();
+    }
+}