A2A Java SDK

![A2A Logo](https://raw.githubusercontent.com/google-a2a/A2A/refs/heads/main/docs/assets/a2a-logo-black.svg)

A Java library that helps run agentic applications as A2A servers following the Agent2Agent (A2A) Protocol.

A multi-module Maven library providing client and server support for A2A agent communication over JSON-RPC, gRPC, and REST transports.

Documentation

Full documentation is available at a2aproject.github.io/a2a-java.

Server Guide — Run your agentic Java application as an A2A server
Client Guide — Communicate with any A2A-compliant agent
Javadoc — Java API reference
Community Articles — Tutorials, blog posts, and videos
Announcements — Release announcements and project news
Contributing — Developer guide for contributing

Quick Start

Requires Java 17+.

Add the A2A Java SDK reference server for JSON-RPC to your Maven project:


    org.a2aproject.sdk
    a2a-java-sdk-reference-jsonrpc
     
    ${org.a2aproject.sdk.version}

See the Server Guide for full setup instructions.

Build

mvn clean install

Regeneration of gRPC files

We copy https://github.com/a2aproject/A2A/blob/main/specification/grpc/a2a.proto to the spec-grpc/ project, and adjust the java_package option to be as follows:

option java_package = "org.a2aproject.sdk.grpc";

Then build the spec-grpc module with mvn clean install -Dskip.protobuf.generate=false to regenerate the gRPC classes in the org.a2aproject.sdk.grpc package.

Examples

Hello World Server — Java A2A server with a Python client
Hello World Client — Java A2A client with a Python server
a2a-samples — More agent examples

Server Integrations

Community contributed integrations with various Java runtimes:

Quarkus — This project contains the reference implementations for JSON-RPC, gRPC, and HTTP+JSON (REST) transports.
Jakarta EE — a2a-jakarta works with any runtime supporting the Jakarta EE Web Profile.

To contribute an integration, see CONTRIBUTING_INTEGRATIONS.md.

Extras

See the extras folder for optional add-ons (OpenTelemetry, JPA-backed task store, Kafka-based replicated queue manager, Vert.x and Android HTTP clients).

License

This project is licensed under the terms of the Apache 2.0 License.

Contributing

See CONTRIBUTING.md for contribution guidelines.