[Fix #1087] A2A implementation by fjtirado · Pull Request #1469 · serverlessworkflow/sdk-java

fjtirado · 2026-06-17T16:24:09Z

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Pull request overview

Adds initial A2A call support to the Serverless Workflow Java implementation (Fix #1087), introducing a new impl-a2a executor module and a basic “hello world” workflow + integration test to validate end-to-end execution via a mocked A2A endpoint.

Changes:

Introduces new serverlessworkflow-impl-a2a module with an A2A task executor and request dispatchers (message send/stream + task operations).
Registers the A2A callable task builder via Java SPI so the implementation can discover the executor at runtime.
Adds an integration test + sample workflow to validate A2A message/send behavior.

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Copilot reviewed 20 out of 20 changed files in this pull request and generated 5 comments.

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File	Description
impl/test/src/test/resources/workflows-samples/a2a/a2a-hello-world.yaml	Adds a sample workflow exercising `call: a2a` with `message/send`.
impl/test/src/test/java/io/serverlessworkflow/impl/test/A2ADefinitionTest.java	Adds an integration-style test using `MockWebServer` to validate A2A execution.
impl/test/pom.xml	Pulls in the new `serverlessworkflow-impl-a2a` module for tests.
impl/pom.xml	Adds the new `a2a` module + dependency management for the A2A SDK and Gson.
impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowError.java	Refactors stacktrace capture into a reusable `getStackTrace(...)` helper.
impl/a2a/src/main/resources/META-INF/services/io.serverlessworkflow.impl.executors.CallableTaskBuilder	Registers `A2AExecutorBuilder` via SPI.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/MessageStreamConsumer.java	Implements streaming event handling for message/task updates.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/MessageSendConsumer.java	Implements non-stream message/task event handling.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/MessageDispatcher.java	Builds/sends A2A messages and returns a future for the workflow result.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/MessageConsumerFactory.java	Centralizes consumer creation and exception handling hookup.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/MessageConsumer.java	Base consumer abstraction returning a `CompletableFuture<WorkflowModel>`.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/ListTaskParamsDispatcher.java	Implements A2A `tasks/list` dispatch and model conversion.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/GetTaskParamsDispatcher.java	Implements A2A `tasks/get` dispatch and model conversion.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/CancelTaskParamsDispatcher.java	Implements A2A `tasks/cancel` dispatch and model conversion.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AUtils.java	Adds parameter extraction/coercion helpers + conversions to `WorkflowModel`.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2ARequestDispatcher.java	Introduces the dispatcher functional interface used by the executor.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AExecutorBuilder.java	Wires `CallA2A` tasks to dispatcher implementations and endpoint resolution.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AExecutor.java	Creates the A2A SDK client and executes the selected dispatcher.
impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AExceptionHandler.java	Maps thrown errors into `WorkflowException` + `WorkflowError` details.
impl/a2a/pom.xml	Adds the Maven module definition for `serverlessworkflow-impl-a2a`.

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Copilot reviewed 20 out of 20 changed files in this pull request and generated 7 comments.

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Copilot reviewed 20 out of 20 changed files in this pull request and generated 5 comments.

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Copilot reviewed 23 out of 23 changed files in this pull request and generated 5 comments.

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Copilot reviewed 23 out of 23 changed files in this pull request and generated 1 comment.

fjtirado · 2026-06-24T17:46:43Z

+          case AGENT_GET_AUTHENTICATED_EXTENDED_CARD,
+              TASKS_PUSH_NOTIFICATION_CONFIG_DELETE,
+              TASKS_PUSH_NOTIFICATION_CONFIG_GET,
+              TASKS_PUSH_NOTIFICATION_CONFIG_LIST,
+              TASKS_PUSH_NOTIFICATION_CONFIG_SET,
+              TASKS_RESUBSCRIBE ->


Since these operations are not really frequent, they will be adressed with a separate issue #1485

fjtirado · 2026-06-24T17:48:50Z

+            <dependency>
+              <groupId>com.google.code.gson</groupId>
+              <artifactId>gson</artifactId>
+              <version>${version.com.google.code.gson}</version>


yes, the a2a SDK is using Gson, google gRPC is also using gson and here we are aligning the two versions to the latest one.

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Signed-off-by: fjtirado <ftirados@ibm.com>

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ricardozanini

Looks solid, but for this use case, shouldn't we implement integration tests with real models?

ricardozanini · 2026-06-24T20:04:36Z

+              try {
+                return dispatcher.apply(
+                    agentCard,
+                    Client.builder(agentCard)


How do we replace this client with a framework's infra?

ricardozanini · 2026-06-24T21:02:19Z

+                optionalParam(parameters, "pageToken", String.class),
+                optionalParam(parameters, "historyLength", Integer.class),
+                optionalParam(parameters, "statusTimestampAfter", Instant.class),
+                optionalParam(parameters, "includeArtifacts", Boolean.class),


In the next iteration, I'd transform all these strings into consts in a A2AConsts style-class to align with their spec.

fjtirado force-pushed the Fix_#1087 branch 9 times, most recently from 85ef704 to baa443a Compare June 22, 2026 11:36

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Comment thread impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AUtils.java

fjtirado force-pushed the Fix_#1087 branch from 0632605 to fba15bf Compare June 24, 2026 16:54

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Comment thread impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AExecutorBuilder.java Outdated

fjtirado force-pushed the Fix_#1087 branch from a10c925 to b29afe1 Compare June 24, 2026 17:36

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Comment thread impl/a2a/src/main/java/io/serverlessworkflow/impl/executors/a2a/A2AUtils.java

[Fix serverlessworkflow#1087] A2A implementation

8758e02

Signed-off-by: fjtirado <ftirados@ibm.com>

fjtirado force-pushed the Fix_#1087 branch from b29afe1 to 8758e02 Compare June 24, 2026 17:54

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fjtirado commented Jun 17, 2026

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fjtirado Jun 24, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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fjtirado Jun 24, 2026 •

edited

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