feat(http-client): add Android support and implement SPI for A2AHttpClient

README.md

@@ -394,7 +394,7 @@ Different transport protocols can be configured with specific settings using spe
 
 ##### JSON-RPC Transport Configuration
 
-For the JSON-RPC transport, to use the default `JdkA2AHttpClient`, provide a `JSONRPCTransportConfig` created with its default constructor.
+For the JSON-RPC transport, to use the default HTTP client (resolved automatically by `A2AHttpClientFactory`), provide a `JSONRPCTransportConfig` created with its default constructor.
 
 To use a custom HTTP client implementation, simply create a `JSONRPCTransportConfig` as follows:
 
@@ -441,7 +441,7 @@ Client client = Client
 
 ##### HTTP+JSON/REST Transport Configuration
 
-For the HTTP+JSON/REST transport, if you'd like to use the default `JdkA2AHttpClient`, provide a `RestTransportConfig` created with its default constructor.
+For the HTTP+JSON/REST transport, to use the default HTTP client (resolved automatically by `A2AHttpClientFactory`), provide a `RestTransportConfig` created with its default constructor.
 
 To use a custom HTTP client implementation, simply create a `RestTransportConfig` as follows:
 

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

@@ -3,11 +3,10 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.UUID;
 
 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;
@@ -139,7 +138,7 @@ private static Message toMessage(List<Part<?>> parts, Message.Role role, String
      * @throws A2AClientJSONError If the response body cannot be decoded as JSON or validated against the AgentCard schema
      */
     public static AgentCard getAgentCard(String agentUrl) throws A2AClientError, A2AClientJSONError {
-        return getAgentCard(new JdkA2AHttpClient(), agentUrl);
+        return getAgentCard(A2AHttpClientFactory.create(), agentUrl);
     }
 
     /**
@@ -167,7 +166,7 @@ public static AgentCard getAgentCard(A2AHttpClient httpClient, String agentUrl)
      * @throws 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/transport/jsonrpc/src/main/java/io/a2a/client/transport/jsonrpc/JSONRPCTransport.java

@@ -14,8 +14,8 @@
 import io.a2a.client.transport.spi.interceptors.ClientCallInterceptor;
 import io.a2a.client.transport.spi.interceptors.PayloadAndHeaders;
 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.spi.ClientTransport;
 import io.a2a.spec.A2AClientError;
 import io.a2a.spec.A2AClientException;
@@ -84,7 +84,7 @@ public JSONRPCTransport(AgentCard agentCard) {
 
     public JSONRPCTransport(A2AHttpClient httpClient, AgentCard agentCard,
                             String agentUrl, List<ClientCallInterceptor> interceptors) {
-        this.httpClient = httpClient == null ? new JdkA2AHttpClient() : httpClient;
+        this.httpClient = httpClient == null ? A2AHttpClientFactory.create() : httpClient;
         this.agentCard = agentCard;
         this.agentUrl = agentUrl;
         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;
 
 public class JSONRPCTransportConfigBuilder extends ClientTransportConfigBuilder<JSONRPCTransportConfig, JSONRPCTransportConfigBuilder> {
@@ -18,7 +18,7 @@ public JSONRPCTransportConfigBuilder httpClient(A2AHttpClient httpClient) {
     public JSONRPCTransportConfig build() {
         // No HTTP client provided, fallback to the default one (JDK-based 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;
@@ -11,7 +11,7 @@ public class JSONRPCTransportProvider implements ClientTransportProvider<JSONRPC
     @Override
     public JSONRPCTransport create(JSONRPCTransportConfig clientTransportConfig, AgentCard agentCard, String agentUrl) throws A2AClientException {
         if (clientTransportConfig == null) {
-            clientTransportConfig = new JSONRPCTransportConfig(new JdkA2AHttpClient());
+            clientTransportConfig = new JSONRPCTransportConfig(A2AHttpClientFactory.create());
         }
 
         return new JSONRPCTransport(clientTransportConfig.getHttpClient(), agentCard, agentUrl, clientTransportConfig.getInterceptors());

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

@@ -8,8 +8,8 @@
 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;
@@ -63,7 +63,7 @@ public RestTransport(AgentCard agentCard) {
 
     public RestTransport(@Nullable A2AHttpClient httpClient, AgentCard agentCard,
             String agentUrl, @Nullable List<ClientCallInterceptor> interceptors) {
-        this.httpClient = httpClient == null ? new JdkA2AHttpClient() : httpClient;
+        this.httpClient = httpClient == null ? A2AHttpClientFactory.create() : httpClient;
         this.agentCard = agentCard;
         this.agentUrl = agentUrl.endsWith("/") ? agentUrl.substring(0, agentUrl.length() - 1) : agentUrl;
         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;
 
@@ -16,9 +16,8 @@ public RestTransportConfigBuilder httpClient(A2AHttpClient httpClient) {
 
     @Override
     public RestTransportConfig build() {
-        // No HTTP client provided, fallback to the default one (JDK-based 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;
@@ -17,9 +17,9 @@ public String getTransportProtocol() {
     public RestTransport create(RestTransportConfig clientTransportConfig, AgentCard agentCard, String agentUrl) throws A2AClientException {
         RestTransportConfig transportConfig = clientTransportConfig;
          if (transportConfig == null) {
-            transportConfig = new RestTransportConfig(new JdkA2AHttpClient());
+            transportConfig = new RestTransportConfig(A2AHttpClientFactory.create());
         }
-        return new RestTransport(clientTransportConfig.getHttpClient(), agentCard, agentUrl, transportConfig.getInterceptors());
+        return new RestTransport(transportConfig.getHttpClient(), agentCard, agentUrl, transportConfig.getInterceptors());
     }
 
     @Override

extras/http-client-android/pom.xml

@@ -0,0 +1,48 @@
+<?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>0.3.4.Beta1-SNAPSHOT</version>
+        <relativePath>../../pom.xml</relativePath>
+    </parent>
+    <artifactId>a2a-java-sdk-http-client-android</artifactId>
+    <packaging>jar</packaging>
+
+    <name>Java SDK A2A HTTP Client: Android</name>
+    <description>Java SDK for the Agent2Agent Protocol (A2A) - Android HTTP Client</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-http-client</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-spec</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-http-client</artifactId>
+            <type>test-jar</type>
+            <scope>test</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>