You can build the A2A Java SDK using mvn:
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 = "io.a2a.grpc";
Then build the spec-grpc module with mvn clean install -Pproto-compile to regenerate the gRPC classes in the io.a2a.grpc package.
You can find an example of how to use the A2A Java SDK in the a2a-samples repository.
More examples will be added soon.
The A2A Java SDK provides a Java server implementation of the Agent2Agent (A2A) Protocol. To run your agentic Java application as an A2A server, simply follow the steps below.
Adding a dependency on an A2A Java SDK Server will provide access to the core classes that make up the A2A specification and allow you to run your agentic Java application as an A2A server agent.
The A2A Java SDK provides a reference A2A server implementation based on Quarkus for use with our tests and examples. However, the project is designed in such a way that it is trivial to integrate with various Java runtimes.
Server Integrations contains a list of community contributed integrations of the server with various runtimes. You might be able to use one of these for your target runtime, or you can use them as inspiration to create your own.
To use the reference implementation with the JSONRPC protocol add the following dependency to your project:
⚠️ The
io.github.a2asdkgroupIdbelow is temporary and will likely change for future releases.
<dependency>
<groupId>io.github.a2asdk</groupId>
<artifactId>a2a-java-sdk-reference-jsonrpc</artifactId>
<!-- Use a released version from https://github.com/a2aproject/a2a-java/releases -->
<version>${io.a2a.sdk.version}</version>
</dependency>
To use the reference implementation with the gRPC protocol add the following dependency to your project:
⚠️ The
io.github.a2asdkgroupIdbelow is temporary and will likely change for future releases.
<dependency>
<groupId>io.github.a2asdk</groupId>
<artifactId>a2a-java-sdk-reference-grpc</artifactId>
<!-- Use a released version from https://github.com/a2aproject/a2a-java/releases -->
<version>${io.a2a.sdk.version}</version>
</dependency> 2. Add a class that creates an A2A Agent Card
import io.a2a.server.PublicAgentCard;
import io.a2a.spec.AgentCapabilities;
import io.a2a.spec.AgentCard;
import io.a2a.spec.AgentSkill;
...
@ApplicationScoped
public class WeatherAgentCardProducer {
@Produces
@PublicAgentCard
public AgentCard agentCard() {
return new AgentCard.Builder()
.name("Weather Agent")
.description("Helps with weather")
.url("http://localhost:10001")
.version("1.0.0")
.capabilities(new AgentCapabilities.Builder()
.streaming(true)
.pushNotifications(false)
.stateTransitionHistory(false)
.build())
.defaultInputModes(Collections.singletonList("text"))
.defaultOutputModes(Collections.singletonList("text"))
.skills(Collections.singletonList(new AgentSkill.Builder()
.id("weather_search")
.name("Search weather")
.description("Helps with weather in city, or states")
.tags(Collections.singletonList("weather"))
.examples(List.of("weather in LA, CA"))
.build()))
.protocolVersion("0.2.5")
.build();
}
} 3. Add a class that creates an A2A Agent Executor
import io.a2a.server.agentexecution.AgentExecutor;
import io.a2a.server.agentexecution.RequestContext;
import io.a2a.server.events.EventQueue;
import io.a2a.server.tasks.TaskUpdater;
import io.a2a.spec.JSONRPCError;
import io.a2a.spec.Message;
import io.a2a.spec.Part;
import io.a2a.spec.Task;
import io.a2a.spec.TaskNotCancelableError;
import io.a2a.spec.TaskState;
import io.a2a.spec.TextPart;
...
@ApplicationScoped
public class WeatherAgentExecutorProducer {
@Inject
WeatherAgent weatherAgent;
@Produces
public AgentExecutor agentExecutor() {
return new WeatherAgentExecutor(weatherAgent);
}
private static class WeatherAgentExecutor implements AgentExecutor {
private final WeatherAgent weatherAgent;
public WeatherAgentExecutor(WeatherAgent weatherAgent) {
this.weatherAgent = weatherAgent;
}
@Override
public void execute(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
TaskUpdater updater = new TaskUpdater(context, eventQueue);
// mark the task as submitted and start working on it
if (context.getTask() == null) {
updater.submit();
}
updater.startWork();
// extract the text from the message
String userMessage = extractTextFromMessage(context.getMessage());
// call the weather agent with the user's message
String response = weatherAgent.chat(userMessage);
// create the response part
TextPart responsePart = new TextPart(response, null);
List<Part<?>> parts = List.of(responsePart);
// add the response as an artifact and complete the task
updater.addArtifact(parts, null, null, null);
updater.complete();
}
@Override
public void cancel(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
Task task = context.getTask();
if (task.getStatus().state() == TaskState.CANCELED) {
// task already cancelled
throw new TaskNotCancelableError();
}
if (task.getStatus().state() == TaskState.COMPLETED) {
// task already completed
throw new TaskNotCancelableError();
}
// cancel the task
TaskUpdater updater = new TaskUpdater(context, eventQueue);
updater.cancel();
}
private String extractTextFromMessage(Message message) {
StringBuilder textBuilder = new StringBuilder();
if (message.getParts() != null) {
for (Part part : message.getParts()) {
if (part instanceof TextPart textPart) {
textBuilder.append(textPart.getText());
}
}
}
return textBuilder.toString();
}
}
}
The A2A Java SDK provides a Java client implementation of the Agent2Agent (A2A) Protocol, allowing communication with A2A servers. To make use of the Java A2AClient, simply add the following dependency:
⚠️ The
io.github.a2asdkgroupIdbelow is temporary and will likely change for future releases.
<dependency>
<groupId>io.github.a2asdk</groupId>
<artifactId>a2a-java-sdk-client</artifactId>
<!-- Use a released version from https://github.com/a2aproject/a2a-java/releases -->
<version>${io.a2a.sdk.version}</version>
</dependency>
// Create an A2AClient (the URL specified is the server agent's URL, be sure to replace it with the actual URL of the A2A server you want to connect to)
A2AClient client = new A2AClient("http://localhost:1234"); Send a message to the A2A server agent
// Send a text message to the A2A server agent
Message message = A2A.toUserMessage("tell me a joke"); // the message ID will be automatically generated for you
MessageSendParams params = new MessageSendParams.Builder()
.message(message)
.build();
SendMessageResponse response = client.sendMessage(params);
Note that A2A#toUserMessage will automatically generate a message ID for you when creating the Message if you don't specify it. You can also explicitly specify a message ID like this:
Message message = A2A.toUserMessage("tell me a joke", "message-1234"); // messageId is message-1234 Get the current state of a task
// Retrieve the task with id "task-1234"
GetTaskResponse response = client.getTask("task-1234");
// You can also specify the maximum number of items of history for the task
// to include in the response
GetTaskResponse response = client.getTask(new TaskQueryParams("task-1234", 10));
// Cancel the task we previously submitted with id "task-1234"
CancelTaskResponse response = client.cancelTask("task-1234");
// You can also specify additional properties using a map
Map<String, Object> metadata = ...
CancelTaskResponse response = client.cancelTask(new TaskIdParams("task-1234", metadata)); Get a push notification configuration for a task
// Get task push notification configuration
GetTaskPushNotificationConfigResponse response = client.getTaskPushNotificationConfig("task-1234");
// The push notification configuration ID can also be optionally specified
GetTaskPushNotificationConfigResponse response = client.getTaskPushNotificationConfig("task-1234", "config-4567");
// Additional properties can be specified using a map
Map<String, Object> metadata = ...
GetTaskPushNotificationConfigResponse response = client.getTaskPushNotificationConfig(new GetTaskPushNotificationConfigParams("task-1234", "config-1234", metadata)); Set a push notification configuration for a task
// Set task push notification configuration
PushNotificationConfig pushNotificationConfig = new PushNotificationConfig.Builder()
.url("https://example.com/callback")
.authenticationInfo(new AuthenticationInfo(Collections.singletonList("jwt"), null))
.build();
SetTaskPushNotificationResponse response = client.setTaskPushNotificationConfig("task-1234", pushNotificationConfig); List the push notification configurations for a task
ListTaskPushNotificationConfigResponse response = client.listTaskPushNotificationConfig("task-1234");
// Additional properties can be specified using a map
Map<String, Object> metadata = ...
ListTaskPushNotificationConfigResponse response = client.listTaskPushNotificationConfig(new ListTaskPushNotificationConfigParams("task-123", metadata)); Delete a push notification configuration for a task
DeleteTaskPushNotificationConfigResponse response = client.deleteTaskPushNotificationConfig("task-1234", "config-4567");
// Additional properties can be specified using a map
Map<String, Object> metadata = ...
DeleteTaskPushNotificationConfigResponse response = client.deleteTaskPushNotificationConfig(new DeleteTaskPushNotificationConfigParams("task-1234", "config-4567", metadata));
// Send a text message to the remote agent
Message message = A2A.toUserMessage("tell me some jokes"); // the message ID will be automatically generated for you
MessageSendParams params = new MessageSendParams.Builder()
.message(message)
.build();
// Create a handler that will be invoked for Task, Message, TaskStatusUpdateEvent, and TaskArtifactUpdateEvent
Consumer<StreamingEventKind> eventHandler = event -> {...};
// Create a handler that will be invoked if an error is received
Consumer<JSONRPCError> errorHandler = error -> {...};
// Create a handler that will be invoked in the event of a failure
Runnable failureHandler = () -> {...};
// Send the streaming message to the remote agent
client.sendStreamingMessage(params, eventHandler, errorHandler, failureHandler);
// Create a handler that will be invoked for Task, Message, TaskStatusUpdateEvent, and TaskArtifactUpdateEvent
Consumer<StreamingEventKind> eventHandler = event -> {...};
// Create a handler that will be invoked if an error is received
Consumer<JSONRPCError> errorHandler = error -> {...};
// Create a handler that will be invoked in the event of a failure
Runnable failureHandler = () -> {...};
// Resubscribe to an ongoing task with id "task-1234"
TaskIdParams taskIdParams = new TaskIdParams("task-1234");
client.resubscribeToTask("request-1234", taskIdParams, eventHandler, errorHandler, failureHandler); Retrieve details about the server agent that this client agent is communicating with
AgentCard serverAgentCard = client.getAgentCard();
An agent card can also be retrieved using the A2A#getAgentCard method:
// http://localhost:1234 is the base URL for the agent whose card we want to retrieve
AgentCard agentCard = A2A.getAgentCard("http://localhost:1234"); Hello World Client Example
A complete example of a Java A2A client communicating with a Python A2A server is available in the examples/helloworld/client directory. This example demonstrates:
The example includes detailed instructions on how to run the Python A2A server and how to run the Java A2A client using JBang.
Check out the example's README for more information.
Hello World Server ExampleA complete example of a Python A2A client communicating with a Java A2A server is available in the examples/helloworld/server directory. This example demonstrates:
AgentCard producerAgentExecutor producerCheck out the example's README for more information.
See COMMUNITY_ARTICLES.md for a list of community articles and videos.
This project is licensed under the terms of the Apache 2.0 License.
See CONTRIBUTING.md for contribution guidelines.
The following list contains community contributed integrations with various Java Runtimes.
To contribute an integration, please see CONTRIBUTING_INTEGRATIONS.md.
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4