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Merge pull request #118 from fjuma/spec
Add details about the A2A server implementation to the README and update the project version to 0.2.3-SNAPSHOT
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‎README.md‎

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# Java A2A SDK (WIP)
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# A2A Java SDK
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This project (currently WIP) will provide a Java SDK implementation of Google's [Agent2Agent protocol (A2A)](https://google.github.io/A2A/).
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<html>
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<h3 align="center">A Java library that helps run agentic applications as A2AServers following Google's <a href="https://google-a2a.github.io/A2A">Agent2Agent (A2A) Protocol</a>.</h3>
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</html>
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## Specification
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## Installation
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The majority of the classes required by the specification can currently be found in the [src/main/java/io/a2a/spec](https://github.com/fjuma/a2a-java-sdk/tree/main/src/main/java/io/a2a/spec) directory.
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You can build the A2A Java SDK using `mvn`:
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```bash
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mvn clean install
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```
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## Examples
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You can find an example of how to use the A2A Java SDK [here](https://github.com/fjuma/a2a-samples/tree/java-sdk-example/samples/multi_language/python_and_java_multiagent/weather_agent).
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More examples will be added soon.
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## A2A Server
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The A2A Java SDK provides a Java server implementation of the [Agent2Agent (A2A) Protocol](https://google-a2a.github.io/A2A). To run your agentic Java application as an A2A server, simply follow the steps below.
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- [Add the A2A Java SDK Core Maven dependency to your project](#1-add-the-a2a-java-sdk-core-maven-dependency-to-your-project)
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- [Add a class that creates an A2A Agent Card](#2-add-a-class-that-creates-an-a2a-agent-card)
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- [Add a class that creates an A2A Agent Executor](#3-add-a-class-that-creates-an-a2a-agent-executor)
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- [Add an A2A Java SDK Server Maven dependency to your project](#4-add-an-a2a-java-sdk-server-maven-dependency-to-your-project)
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### 1. Add the A2A Java SDK Core Maven dependency to your project
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> **Note**: The A2A Java SDK isn't available yet in Maven Central but will be soon. For now, be
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> sure to check out the latest tag (you can see the tags [here](https://github.com/fjuma/a2a-java-sdk/tags)), build from the tag, and reference that version below. For example, if the latest tag is `0.2.3`, you can use the following dependency.
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```xml
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<dependency>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-core</artifactId>
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<version>0.2.3</version>
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</dependency>
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```
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### 2. Add a class that creates an A2A Agent Card
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```java
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import io.a2a.spec.AgentCapabilities;
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import io.a2a.spec.AgentCard;
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import io.a2a.spec.AgentSkill;
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import io.a2a.spec.PublicAgentCard;
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...
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@ApplicationScoped
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public class WeatherAgentCardProducer {
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@Produces
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@PublicAgentCard
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public AgentCard agentCard() {
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return new AgentCard.Builder()
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.name("Weather Agent")
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.description("Helps with weather")
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.url("http://localhost:10001")
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.version("1.0.0")
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.capabilities(new AgentCapabilities.Builder()
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.streaming(true)
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.pushNotifications(false)
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.stateTransitionHistory(false)
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.build())
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.defaultInputModes(Collections.singletonList("text"))
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.defaultOutputModes(Collections.singletonList("text"))
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.skills(Collections.singletonList(new AgentSkill.Builder()
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.id("weather_search")
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.name("Search weather")
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.description("Helps with weather in city, or states")
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.tags(Collections.singletonList("weather"))
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.examples(List.of("weather in LA, CA"))
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.build()))
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.build();
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}
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}
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```
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### 3. Add a class that creates an A2A Agent Executor
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```java
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import io.a2a.server.agentexecution.AgentExecutor;
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import io.a2a.server.agentexecution.RequestContext;
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import io.a2a.server.events.EventQueue;
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import io.a2a.server.tasks.TaskUpdater;
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import io.a2a.spec.JSONRPCError;
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import io.a2a.spec.Message;
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import io.a2a.spec.Part;
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import io.a2a.spec.Task;
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import io.a2a.spec.TaskNotCancelableError;
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import io.a2a.spec.TaskState;
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import io.a2a.spec.TextPart;
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...
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@ApplicationScoped
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public class WeatherAgentExecutorProducer {
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@Inject
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WeatherAgent weatherAgent;
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@Produces
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public AgentExecutor agentExecutor() {
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return new WeatherAgentExecutor(weatherAgent);
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}
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private static class WeatherAgentExecutor implements AgentExecutor {
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private final WeatherAgent weatherAgent;
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public WeatherAgentExecutor(WeatherAgent weatherAgent) {
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this.weatherAgent = weatherAgent;
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}
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@Override
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public void execute(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
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TaskUpdater updater = new TaskUpdater(context, eventQueue);
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// mark the task as submitted and start working on it
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if (context.getTask() == null) {
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updater.submit();
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}
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updater.startWork();
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// extract the text from the message
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String userMessage = extractTextFromMessage(context.getMessage());
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// call the weather agent with the user's message
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String response = weatherAgent.chat(userMessage);
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// create the response part
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TextPart responsePart = new TextPart(response, null);
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List<Part<?>> parts = List.of(responsePart);
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// add the response as an artifact and complete the task
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updater.addArtifact(parts, null, null, null);
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updater.complete();
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}
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private String extractTextFromMessage(Message message) {
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StringBuilder textBuilder = new StringBuilder();
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if (message.getParts() != null) {
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for (Part part : message.getParts()) {
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if (part instanceof TextPart textPart) {
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textBuilder.append(textPart.getText());
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}
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}
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}
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return textBuilder.toString();
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}
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@Override
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public void cancel(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
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Task task = context.getTask();
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if (task.getStatus().state() == TaskState.CANCELED) {
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// task already cancelled
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throw new TaskNotCancelableError();
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}
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if (task.getStatus().state() == TaskState.COMPLETED) {
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// task already completed
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throw new TaskNotCancelableError();
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}
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// cancel the task
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TaskUpdater updater = new TaskUpdater(context, eventQueue);
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updater.cancel();
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}
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}
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}
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```
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### 4. Add an A2A Java SDK Server Maven dependency to your project
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> **Note**: The A2A Java SDK isn't available yet in Maven Central but will be soon. For now, be
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> sure to check out the latest tag (you can see the tags [here](https://github.com/fjuma/a2a-java-sdk/tags)), build from the tag, and reference that version below. For example, if the latest tag is `0.2.3`, you can use the following dependency.
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Adding a dependency on an A2A Java SDK Server will allow you to run your agentic Java application as an A2A server.
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The A2A Java SDK provides two A2A server endpoint implementations, one based on Jakarta REST (`a2a-java-sdk-server-jakarta`) and one based on Quarkus Reactive Routes (`a2a-java-sdk-server-quarkus`). You can choose the one that best fits your application.
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Add **one** of the following dependencies to your project:
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```xml
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<dependency>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-server-jakarta</artifactId>
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<version>${io.a2a.sdk.version}</version>
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</dependency>
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```
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OR
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```xml
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<dependency>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-server-quarkus</artifactId>
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<version>${io.a2a.sdk.version}</version>
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</dependency>
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```
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## Client
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‎core/pom.xml‎

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<parent>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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</parent>
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<artifactId>a2a-java-sdk-core</artifactId>
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‎examples/pom.xml‎

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<parent>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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</parent>
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<artifactId>a2a-java-sdk-examples</artifactId>

‎examples/src/main/java/io/a2a/examples/helloworld/client/HelloWorldRunner.java‎

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///usr/bin/env jbang "$0" "$@" ; exit $?
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//REPOS file://~/.m2/repository/
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//DEPS io.a2a.sdk:a2a-java-sdk:1.0.0-SNAPSHOT
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//DEPS io.a2a.sdk:a2a-java-sdk:0.2.3-SNAPSHOT
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//SOURCES HelloWorldClient.java
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/**

‎pom.xml‎

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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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<packaging>pom</packaging>
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‎sdk-jakarta/pom.xml‎

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<parent>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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</parent>
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<artifactId>a2a-java-sdk-server-jakarta</artifactId>
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‎sdk-quarkus/pom.xml‎

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<parent>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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</parent>
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<artifactId>a2a-java-sdk-server-quarkus</artifactId>
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‎tck/pom.xml‎

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<parent>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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</parent>
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<artifactId>a2a-tck-server</artifactId>

‎tests/server-common/pom.xml‎

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<parent>
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<groupId>io.a2a.sdk</groupId>
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<artifactId>a2a-java-sdk-parent</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<version>0.2.3-SNAPSHOT</version>
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<relativePath>../../pom.xml</relativePath>
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</parent>
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<artifactId>a2a-java-sdk-tests-server-common</artifactId>

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