feat: Add pluggable A2AHttpClient with Vert.x implementation

boms/extras/pom.xml

@@ -34,6 +34,11 @@
                 <artifactId>a2a-java-extras-common</artifactId>
                 <version>${project.version}</version>
             </dependency>
+            <dependency>
+                <groupId>${project.groupId}</groupId>
+                <artifactId>a2a-java-sdk-http-client-vertx</artifactId>
+                <version>${project.version}</version>
+            </dependency>
             <dependency>
                 <groupId>${project.groupId}</groupId>
                 <artifactId>a2a-java-extras-task-store-database-jpa</artifactId>

boms/extras/src/it/extras-usage-test/pom.xml

@@ -44,6 +44,10 @@
             <groupId>io.github.a2asdk</groupId>
             <artifactId>a2a-java-extras-common</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.github.a2asdk</groupId>
+            <artifactId>a2a-java-sdk-http-client-vertx</artifactId>
+        </dependency>
         <dependency>
             <groupId>io.github.a2asdk</groupId>
             <artifactId>a2a-java-extras-task-store-database-jpa</artifactId>

client/base/pom.xml

@@ -22,6 +22,11 @@
             <groupId>${project.groupId}</groupId>
             <artifactId>a2a-java-sdk-http-client</artifactId>
         </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-http-client-vertx</artifactId>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>${project.groupId}</groupId>
             <artifactId>a2a-java-sdk-client-transport-spi</artifactId>

client/base/src/main/java/io/a2a/A2A.java

@@ -6,7 +6,7 @@
 
 import io.a2a.client.http.A2ACardResolver;
 import io.a2a.client.http.A2AHttpClient;
-import io.a2a.client.http.JdkA2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.spec.A2AClientError;
 import io.a2a.spec.A2AClientJSONError;
 import io.a2a.spec.AgentCard;
@@ -286,7 +286,7 @@ private static Message toMessage(List<Part<?>> parts, Message.Role role, String
      * @see AgentCard
      */
     public static AgentCard getAgentCard(String agentUrl) throws A2AClientError, A2AClientJSONError {
-        return getAgentCard(new JdkA2AHttpClient(), agentUrl);
+        return getAgentCard(A2AHttpClientFactory.create(), agentUrl);
     }
 
     /**
@@ -357,7 +357,7 @@ public static AgentCard getAgentCard(A2AHttpClient httpClient, String agentUrl)
      * @throws io.a2a.spec.A2AClientJSONError if the response body cannot be decoded as JSON or validated against the AgentCard schema
      */
     public static AgentCard getAgentCard(String agentUrl, String relativeCardPath, Map<String, String> authHeaders) throws A2AClientError, A2AClientJSONError {
-        return getAgentCard(new JdkA2AHttpClient(), agentUrl, relativeCardPath, authHeaders);
+        return getAgentCard(A2AHttpClientFactory.create(), agentUrl, relativeCardPath, authHeaders);
     }
 
     /**

client/base/src/test/java/io/a2a/client/ClientBuilderTest.java

@@ -6,7 +6,7 @@
 import java.util.List;
 
 import io.a2a.client.config.ClientConfig;
-import io.a2a.client.http.JdkA2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.transport.grpc.GrpcTransport;
 import io.a2a.client.transport.grpc.GrpcTransportConfigBuilder;
 import io.a2a.client.transport.jsonrpc.JSONRPCTransport;
@@ -89,7 +89,7 @@ public void shouldCreateClient_differentConfigurations() throws A2AClientExcepti
         Client client = Client
                 .builder(card)
                 .withTransport(JSONRPCTransport.class, new JSONRPCTransportConfigBuilder())
-                .withTransport(JSONRPCTransport.class, new JSONRPCTransportConfig(new JdkA2AHttpClient()))
+                .withTransport(JSONRPCTransport.class, new JSONRPCTransportConfig(A2AHttpClientFactory.create()))
                 .build();
 
         Assertions.assertNotNull(client);

client/transport/jsonrpc/src/main/java/io/a2a/client/transport/jsonrpc/JSONRPCTransport.java

@@ -23,8 +23,8 @@
 import com.google.protobuf.MessageOrBuilder;
 import io.a2a.client.http.A2ACardResolver;
 import io.a2a.client.http.A2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.http.A2AHttpResponse;
-import io.a2a.client.http.JdkA2AHttpClient;
 import io.a2a.client.transport.jsonrpc.sse.SSEEventListener;
 import io.a2a.client.transport.spi.ClientTransport;
 import io.a2a.client.transport.spi.interceptors.ClientCallContext;
@@ -84,7 +84,7 @@ public JSONRPCTransport(AgentCard agentCard) {
 
     public JSONRPCTransport(@Nullable A2AHttpClient httpClient, @Nullable AgentCard agentCard,
                             AgentInterface agentInterface, @Nullable List<ClientCallInterceptor> interceptors) {
-        this.httpClient = httpClient == null ? new JdkA2AHttpClient() : httpClient;
+        this.httpClient = httpClient == null ? A2AHttpClientFactory.create() : httpClient;
         this.agentCard = agentCard;
         this.agentInterface = agentInterface;
         this.interceptors = interceptors;

client/transport/jsonrpc/src/main/java/io/a2a/client/transport/jsonrpc/JSONRPCTransportConfigBuilder.java

@@ -1,7 +1,7 @@
 package io.a2a.client.transport.jsonrpc;
 
 import io.a2a.client.http.A2AHttpClient;
-import io.a2a.client.http.JdkA2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.transport.spi.ClientTransportConfigBuilder;
 import org.jspecify.annotations.Nullable;
 
@@ -11,7 +11,7 @@
  * This builder provides a fluent API for configuring the JSON-RPC transport protocol.
  * All configuration options are optional - if not specified, sensible defaults are used:
  * <ul>
- *   <li><b>HTTP client:</b> {@link JdkA2AHttpClient} (JDK's built-in HTTP client)</li>
+ *   <li><b>HTTP client:</b> Auto-selected via {@link A2AHttpClientFactory} (prefers Vert.x, falls back to JDK)</li>
  *   <li><b>Interceptors:</b> None</li>
  * </ul>
  * <p>
@@ -78,7 +78,7 @@ public class JSONRPCTransportConfigBuilder extends ClientTransportConfigBuilder<
      *   <li>Custom header handling</li>
      * </ul>
      * <p>
-     * If not specified, the default {@link JdkA2AHttpClient} is used.
+     * If not specified, a client is auto-selected via {@link A2AHttpClientFactory}.
      * <p>
      * Example:
      * <pre>{@code
@@ -101,16 +101,16 @@ public JSONRPCTransportConfigBuilder httpClient(A2AHttpClient httpClient) {
     /**
      * Build the JSON-RPC transport configuration.
      * <p>
-     * If no HTTP client was configured, the default {@link JdkA2AHttpClient} is used.
+     * If no HTTP client was configured, one is auto-selected via {@link A2AHttpClientFactory}.
      * Any configured interceptors are transferred to the configuration.
      *
      * @return the configured JSON-RPC transport configuration
      */
     @Override
     public JSONRPCTransportConfig build() {
-        // No HTTP client provided, fallback to the default one (JDK-based implementation)
+        // No HTTP client provided, use factory to get best available implementation
         if (httpClient == null) {
-            httpClient = new JdkA2AHttpClient();
+            httpClient = A2AHttpClientFactory.create();
         }
 
         JSONRPCTransportConfig config = new JSONRPCTransportConfig(httpClient);

client/transport/jsonrpc/src/main/java/io/a2a/client/transport/jsonrpc/JSONRPCTransportProvider.java

@@ -1,6 +1,6 @@
 package io.a2a.client.transport.jsonrpc;
 
-import io.a2a.client.http.JdkA2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.transport.spi.ClientTransportProvider;
 import io.a2a.spec.A2AClientException;
 import io.a2a.spec.AgentCard;
@@ -14,7 +14,7 @@ public class JSONRPCTransportProvider implements ClientTransportProvider<JSONRPC
     public JSONRPCTransport create(@Nullable JSONRPCTransportConfig clientTransportConfig, AgentCard agentCard, AgentInterface agentInterface) throws A2AClientException {
         JSONRPCTransportConfig currentClientTransportConfig = clientTransportConfig;
         if (currentClientTransportConfig == null) {
-            currentClientTransportConfig = new JSONRPCTransportConfig(new JdkA2AHttpClient());
+            currentClientTransportConfig = new JSONRPCTransportConfig(A2AHttpClientFactory.create());
         }
         return new JSONRPCTransport(currentClientTransportConfig.getHttpClient(), agentCard, agentInterface, currentClientTransportConfig.getInterceptors());
     }

client/transport/rest/src/main/java/io/a2a/client/transport/rest/RestTransport.java

@@ -29,8 +29,8 @@
 import com.google.protobuf.util.JsonFormat;
 import io.a2a.client.http.A2ACardResolver;
 import io.a2a.client.http.A2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.http.A2AHttpResponse;
-import io.a2a.client.http.JdkA2AHttpClient;
 import io.a2a.client.transport.rest.sse.RestSSEEventListener;
 import io.a2a.client.transport.spi.ClientTransport;
 import io.a2a.client.transport.spi.interceptors.ClientCallContext;
@@ -74,7 +74,7 @@ public RestTransport(AgentCard agentCard) {
 
     public RestTransport(@Nullable A2AHttpClient httpClient, AgentCard agentCard,
             AgentInterface agentInterface, @Nullable List<ClientCallInterceptor> interceptors) {
-        this.httpClient = httpClient == null ? new JdkA2AHttpClient() : httpClient;
+        this.httpClient = httpClient == null ? A2AHttpClientFactory.create() : httpClient;
         this.agentCard = agentCard;
         this.agentInterface = agentInterface;
         this.interceptors = interceptors;

client/transport/rest/src/main/java/io/a2a/client/transport/rest/RestTransportConfigBuilder.java

@@ -1,7 +1,7 @@
 package io.a2a.client.transport.rest;
 
 import io.a2a.client.http.A2AHttpClient;
-import io.a2a.client.http.JdkA2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.transport.spi.ClientTransportConfigBuilder;
 import org.jspecify.annotations.Nullable;
 
@@ -11,7 +11,7 @@
  * This builder provides a fluent API for configuring the REST transport protocol.
  * All configuration options are optional - if not specified, sensible defaults are used:
  * <ul>
- *   <li><b>HTTP client:</b> {@link JdkA2AHttpClient} (JDK's built-in HTTP client)</li>
+ *   <li><b>HTTP client:</b> Auto-selected via {@link A2AHttpClientFactory} (prefers Vert.x, falls back to JDK)</li>
  *   <li><b>Interceptors:</b> None</li>
  * </ul>
  * <p>
@@ -78,7 +78,7 @@ public class RestTransportConfigBuilder extends ClientTransportConfigBuilder<Res
      *   <li>Custom header handling</li>
      * </ul>
      * <p>
-     * If not specified, the default {@link JdkA2AHttpClient} is used.
+     * If not specified, a client is auto-selected via {@link A2AHttpClientFactory}.
      * <p>
      * Example:
      * <pre>{@code
@@ -101,16 +101,16 @@ public RestTransportConfigBuilder httpClient(A2AHttpClient httpClient) {
     /**
      * Build the REST transport configuration.
      * <p>
-     * If no HTTP client was configured, the default {@link JdkA2AHttpClient} is used.
+     * If no HTTP client was configured, one is auto-selected via {@link A2AHttpClientFactory}.
      * Any configured interceptors are transferred to the configuration.
      *
      * @return the configured REST transport configuration
      */
     @Override
     public RestTransportConfig build() {
-        // No HTTP client provided, fallback to the default one (JDK-based implementation)
+        // No HTTP client provided, use factory to get best available implementation
         if (httpClient == null) {
-            httpClient = new JdkA2AHttpClient();
+            httpClient = A2AHttpClientFactory.create();
         }
 
         RestTransportConfig config = new RestTransportConfig(httpClient);

client/transport/rest/src/main/java/io/a2a/client/transport/rest/RestTransportProvider.java

@@ -1,6 +1,6 @@
 package io.a2a.client.transport.rest;
 
-import io.a2a.client.http.JdkA2AHttpClient;
+import io.a2a.client.http.A2AHttpClientFactory;
 import io.a2a.client.transport.spi.ClientTransportProvider;
 import io.a2a.spec.A2AClientException;
 import io.a2a.spec.AgentCard;
@@ -18,9 +18,9 @@ public String getTransportProtocol() {
     public RestTransport create(RestTransportConfig clientTransportConfig, AgentCard agentCard, AgentInterface agentInterface) throws A2AClientException {
         RestTransportConfig transportConfig = clientTransportConfig;
          if (transportConfig == null) {
-            transportConfig = new RestTransportConfig(new JdkA2AHttpClient());
+            transportConfig = new RestTransportConfig(A2AHttpClientFactory.create());
         }
-        return new RestTransport(clientTransportConfig.getHttpClient(), agentCard, agentInterface, transportConfig.getInterceptors());
+        return new RestTransport(transportConfig.getHttpClient(), agentCard, agentInterface, transportConfig.getInterceptors());
     }
 
     @Override

extras/http-client-vertx/pom.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>io.github.a2asdk</groupId>
+        <artifactId>a2a-java-sdk-parent</artifactId>
+        <version>1.0.0.Alpha1-SNAPSHOT</version>
+        <relativePath>../../pom.xml</relativePath>
+    </parent>
+    <artifactId>a2a-java-sdk-http-client-vertx</artifactId>
+
+    <packaging>jar</packaging>
+
+    <name>Java SDK A2A HTTP Client - Vert.x Implementation</name>
+    <description>Vert.x implementation for A2A HTTP Client</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-http-client</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.vertx</groupId>
+            <artifactId>vertx-web-client</artifactId>
+            <scope>provided</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mock-server</groupId>
+            <artifactId>mockserver-netty</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>