Sample implementation in Java

[melvinjlobos]

Hi, Do you plan to have a sample implementation in Java? Thanks!

[Kevin1466]

Maybe it should hava a Java SDK before a Java sample.

[myh66]

mark

[vishalmysore]

https://github.com/vishalmysore/a2ajava

[sing1ee]

added to A2A Directory

[vishalmysore]

Thanks a lot

[melvinjlobos]

Thanks @vishalmysore !

[msaleme]

Update: Published a full AIUC-1 crosswalk mapping all 209 tests (including the A2A and x402 harnesses) to the new AI agent certification standard.

AIUC-1 requires quarterly third-party adversarial testing. The A2A-specific tests (Agent Card spoofing, task lifecycle hijacking, push notification abuse, cross-session leakage) map to B001 (adversarial robustness) and D003/D004 (tool call security). Relevant for anyone deploying A2A agents in enterprise environments where AIUC-1 certification may be on the procurement checklist.

[kinthaiofficial]

A Java A2A implementation would be valuable for enterprise environments where Java is the dominant backend language — and the JVM ecosystem has some properties that are interesting for agent systems.

A few things worth considering in the Java implementation design:

Project Loom virtual threads — A2A agents need to handle many concurrent task streams. With virtual threads (Java 21+), you can have thousands of concurrent agent task handlers without the thread pool overhead. This maps naturally to the A2A model where each task has its own execution lifecycle.

Type-safe A2A messages — Java's type system is stronger than most dynamic languages. Using records or sealed classes for A2A message types (TaskStatus, TaskRequest, AgentCard) with Jackson serialization gives you compile-time correctness guarantees that catch protocol implementation errors early.

Agent capability manifest as a Java interface — define a Java interface A2AAgent { AgentCard getCapabilities(); CompletableFuture<TaskResult> executeTask(TaskRequest request); } that any A2A-compatible agent implements. This makes the protocol boundary explicit and testable.

Cost propagation in the call stack — Java's thread-local or scoped values (JEP 429) can carry delegation context and budget through the call stack without requiring explicit parameter passing. Each executeTask call carries the originating budget ceiling.

Spring integration — most Java enterprise services are Spring-based. A Spring Boot auto-configuration for A2A server/client would dramatically lower adoption friction.

We'd be interested in comparing notes on the delegation and budget propagation design if you're working on the Java SDK: https://blog.kinthai.ai/221-agents-multi-agent-coordination-lessons covers our approach.

Is this a community-driven implementation or is Google planning an official Java SDK?