Add a blog post about the A2A Java SDK 0.3.0.Beta1 release

_posts/2025-09-18-quarkus-a2a-java-0-3-0-beta-release.adoc

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+---
+layout: post
+title: 'A2A Java SDK: Support for the REST Transport is Now Here'
+date: 2025-09-18
+tags: ai a2a
+synopsis: 'Today, we released A2A Java SDK 0.3.0.Beta1 which adds support for the HTTP+JSON/REST transport.'
+author: fjuma
+---
+
+Today, we've released A2A Java SDK 0.3.0.Beta1 which introduces support for the HTTP+JSON/REST transport.
+
+Our last https://quarkus.io/blog/quarkus-a2a-java-0-3-0-alpha-release/[blog post] covered what's new in the 0.3.0 version of the A2A Java SDK. In this post, we'll focus on how to make use of the new HTTP+JSON/REST transport for both A2A server agents and clients.
+
+== Configuring an A2A Server Agent to Support the REST Transport
+
+To enable your A2A server agent to support communication using HTTP+JSON/REST, add the following dependency:
+
+[NOTE]
+====
+The `io.github.a2asdk` `groupId` is temporary and will likely change for future releases. Keep an eye on the `a2a-java` https://github.com/a2aproject/a2a-java/blob/main/README.md[README] for up-to-date documentation.
+====
+
+[source,xml]
+----
+<dependency>
+    <groupId>io.github.a2asdk</groupId>
+    <artifactId>a2a-java-sdk-reference-rest</artifactId> <1>
+</dependency>
+----
+
+<1> `a2a-java-sdk-reference-rest` provides access to the core classes that make up the A2A specification and provides the HTTP endpoints that implement the A2A protocol using the HTTP+JSON/REST transport.
+
+After adding this dependency, simply update your agent card to declare support for this new transport:
+
+[source,java]
+----
+@Produces
+@PublicAgentCard
+public AgentCard agentCard() {
+    return new AgentCard.Builder()
+             .url(YOUR_HTTP_JSON_URL) <1>
+             .preferredTransport(TransportProtocol.HTTP_JSON.asString()) <2>
+             .additionalInterfaces(List.of(
+                     new AgentInterface(TransportProtocol.HTTP_JSON.asString(),
+                                        YOUR_HTTP_JSON_URL)
+                     ... <3>
+             ))
+             ...
+             .build();
+}
+----
+
+<1> This is the primary URL for your A2A server agent. This should be the URL for your preferred transport (e.g., `http://localhost:8080`).
+<2> Your A2A server agent's preferred transport, HTTP+JSON/REST in this example.
+<3> The `additionalInterfaces` can optionally contain an entry for the preferred transport. Any other transports you'd like to support (e.g., `TransportProtocol.JSONRPC.asString()` or `TransportProtocol.GRPC.asString()`) can be specified here too.
+
+For more details on configuring your A2A server agent to support multiple transports, refer to our previous https://quarkus.io/blog/quarkus-a2a-java-0-3-0-alpha-release/[blog post].
+
+== Configuring an A2A Client to Support the REST Transport
+
+To get your A2A client to communicate using the HTTP+JSON/REST transport, you'll need to add a couple
+dependencies.
+
+First, add the `a2a-java-sdk-client` dependency to your project. This will provide access to a `Builder` that you can use to create your A2A `Client`.
+
+[source,xml]
+----
+<dependency>
+    <groupId>io.github.a2asdk</groupId>
+    <artifactId>a2a-java-sdk-client</artifactId> <1>
+</dependency>
+----
+
+Next, add the specific dependency for the HTTP+JSON/REST transport:
+
+[source,xml]
+----
+<dependency>
+    <groupId>io.github.a2asdk</groupId>
+    <artifactId>a2a-java-sdk-client-transport-rest</artifactId>
+</dependency>
+----
+
+You can now use `Client.builder()` to create a `Client` that supports the HTTP+JSON/REST transport using the `withTransport` method as shown below:
+
+[source,java]
+----
+// Create the client using the builder
+Client client = Client
+        .builder(agentCard)
+        .withTransport(RestTransport.class, new RestTransportConfig()) <1>
+        ....
+        .build();
+----
+<1> This specifies that our client can support the HTTP+JSON/REST transport. At least one transport must be configured using the `withTransport` method.
+
+For a deep dive into creating clients with the `Client.Builder`, check out this https://quarkus.io/blog/quarkus-a2a-java-0-3-0-alpha-release/[post].
+
+== Conclusion
+
+With the release of A2A Java SDK 0.3.0.Beta1, building flexible, interoperable multi-agent systems just got easier with the new support for the HTTP+JSON/REST transport.
+
+=== Further Reading
+
+* https://quarkus.io/blog/quarkus-a2a-java-0-3-0-alpha-release/[Getting Started with Quarkus and A2A Java SDK 0.3.0]
+* https://github.com/a2aproject/a2a-samples/tree/main/samples/java/agents[A2A Java SDK Samples]
+* https://github.com/a2aproject/a2a-java/blob/main/README.md[A2A Java SDK Documentation]
+* https://a2a-protocol.org/latest/specification/[A2A Specification]
+
+