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Posted to dev@eventmesh.apache.org by "Lyin-OTTF (via GitHub)" <gi...@apache.org> on 2026/10/20 13:23:04 UTC

[PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Lyin-OTTF opened a new pull request, #5430:
URL: https://github.com/apache/eventmesh/pull/5430

   Fixes #5226.
   
   The client/server examples in `docs/a2a-protocol/` call `new A2AProtocolTransportObject(...)`, but that type is not part of the public SDK: in the code it only exists as the private inner class `SimpleA2AProtocolTransportObject` inside `EnhancedA2AProtocolAdaptor`, so the snippet cannot compile as written.
   
   This PR replaces the examples with the path used by the shipped example `eventmesh-examples/src/main/java/org/apache/eventmesh/a2a/demo/mcp/McpCaller.java` and by section 5.1.3 of `docs/feature/a2a.md`:
   
   - client: wrap the JSON-RPC payload in a CloudEvent whose type is `org.apache.eventmesh.a2a.tools.call.req` and which carries the `protocol=A2A` extension, then `producer.publish(event)`;
   - server: publish the JSON-RPC response the same way with type `org.apache.eventmesh.a2a.common.response`, and document the ingress mapping the adaptor performs (`mcptype=response`, `collaborationid=<request id>`, per `EnhancedA2AProtocolAdaptor`).
   
   Also fixes the broken Java string concatenation in the Chinese server example and adds a note that `A2AProtocolTransportObject` is an internal adaptor type.


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Re: [PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Posted by "Lyin-OTTF (via GitHub)" <gi...@apache.org>.

Lyin-OTTF commented on PR #5430:
URL: https://github.com/apache/eventmesh/pull/5430#issuecomment-6306921818

   develop has the same problem: docs/feature/a2a.md lines 754 and 779 still call `new A2AProtocolTransportObject(mcpRequest)` / `(mcpResponse)`, which is the private inner class `SimpleA2AProtocolTransportObject` in `EnhancedA2AProtocolAdaptor` and cannot compile as written. The a2a-protocol/ directory only exists on master, so this PR fixes the master copy.
   
   I can either retarget this PR to develop and fix docs/feature/a2a.md there instead, or keep this one for master and open a second PR against develop for a2a.md. Which do you prefer?
   
   I'll also go through the Copilot suggestions on the missing `mcptype` extensions and `getDataContentType()` in the builders — will push a follow-up commit once I've verified them against McpCaller.


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Re: [PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Posted by "qqeasonchen (via GitHub)" <gi...@apache.org>.

qqeasonchen commented on PR #5430:
URL: https://github.com/apache/eventmesh/pull/5430#issuecomment-6305846593

   @Lyin-OTTF what about develop branch?


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Re: [PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Posted by "Lyin-OTTF (via GitHub)" <gi...@apache.org>.

Lyin-OTTF commented on PR #5430:
URL: https://github.com/apache/eventmesh/pull/5430#issuecomment-6308814032

Pushed a follow-up commit for both Copilot threads (82253de).

Both points check out against the code:

- `McpProvider.handleCallback` dispatches on the `mcptype` extension, and `mcptype`, `a2amethod`, `targetagent` and `collaborationid` are only filled in by `EnhancedA2AProtocolAdaptor` while it converts JSON-RPC to a CloudEvent. Code that publishes the CloudEvent itself never goes through that conversion, so it has to set them. The examples now do, on both the request and the response side.
- `CloudEventProducer.buildCommonPostParam` calls `EventFormatProvider.resolveFormat(cloudEvent.getDataContentType())` and throws when that returns null. The examples now set `application/cloudevents+json`, the same value as `ExampleConstants.CLOUDEVENT_CONTENT_TYPE` used by `McpCaller`, and the subject carries the topic on both builders.

The sentence claiming the adaptor adds `mcptype=response` and `collaborationid` on ingress only holds for the JSON-RPC path, so I replaced it with a note that direct publishers have to set these extensions themselves.

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Re: [PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Posted by "Copilot (via GitHub)" <gi...@apache.org>.

Copilot commented on code in PR #5430:
URL: https://github.com/apache/eventmesh/pull/5430#discussion_r4332243302


##########
docs/a2a-protocol/README_EN.md:
##########
@@ -111,21 +111,63 @@ To support the MCP Request/Response model within an event-driven architecture, A
 ### 1. Initiate Call (Client)
 
 ```java
-// 1. Construct MCP Request JSON
-String mcpRequest = "{" +
-    "\"jsonrpc\": \"2.0\"," +
-    "\"method\": \"tools/call\"," +
-    "\"params\": { \"name\": \"weather\", \"_agentId\": \"weather-agent\" }," +
-    "\"id\": \"req-001\"" +
-    "}";
-
-// 2. Send via EventMesh SDK
-eventMeshProducer.publish(new A2AProtocolTransportObject(mcpRequest));
+// 1. Construct the MCP request payload (JSON-RPC 2.0)
+Map<String, Object> params = new HashMap<>();
+params.put("name", "weather");
+params.put("_agentId", "weather-agent"); // routing hint
+
+Map<String, Object> request = new HashMap<>();
+request.put("jsonrpc", "2.0");
+request.put("method", "tools/call");
+request.put("params", params);
+request.put("id", "req-001");
+
+// 2. Wrap it as a CloudEvent. The "org.apache.eventmesh.a2a." type prefix
+//    together with the protocol=A2A extension triggers the A2A adaptor.

Review Comment:
   The HTTP SDK selects CloudEvents ingress through its transport header, not A2A ingress through these event attributes. That path deserializes the CloudEvent without converting its JSON-RPC data. Consequently the request lacks `mcptype=request` (so `McpProvider.handleCallback` ignores it), and the server response does not acquire the `mcptype` or `collaborationid` promised below. In both READMEs, explicitly set the request extensions `mcptype=request`, `a2amethod=tools/call`, and `targetagent=weather-agent`, and the response extensions `mcptype=response` and `collaborationid=<request id>`. Correct both explanations to distinguish direct CloudEvent publication from raw JSON-RPC conversion by `EnhancedA2AProtocolAdaptor`.



##########
docs/a2a-protocol/README_EN.md:
##########
@@ -111,21 +111,63 @@ To support the MCP Request/Response model within an event-driven architecture, A
 ### 1. Initiate Call (Client)
 
 ```java
-// 1. Construct MCP Request JSON
-String mcpRequest = "{" +
-    "\"jsonrpc\": \"2.0\"," +
-    "\"method\": \"tools/call\"," +
-    "\"params\": { \"name\": \"weather\", \"_agentId\": \"weather-agent\" }," +
-    "\"id\": \"req-001\"" +
-    "}";
-
-// 2. Send via EventMesh SDK
-eventMeshProducer.publish(new A2AProtocolTransportObject(mcpRequest));
+// 1. Construct the MCP request payload (JSON-RPC 2.0)
+Map<String, Object> params = new HashMap<>();
+params.put("name", "weather");
+params.put("_agentId", "weather-agent"); // routing hint
+
+Map<String, Object> request = new HashMap<>();
+request.put("jsonrpc", "2.0");
+request.put("method", "tools/call");
+request.put("params", params);
+request.put("id", "req-001");
+
+// 2. Wrap it as a CloudEvent. The "org.apache.eventmesh.a2a." type prefix
+//    together with the protocol=A2A extension triggers the A2A adaptor.
+CloudEvent event = CloudEventBuilder.v1()
+    .withId("req-001")
+    .withSource(URI.create("mcp-client"))
+    .withType("org.apache.eventmesh.a2a.tools.call.req")

Review Comment:
   Both client and server builders in both READMEs omit fields required by the HTTP SDK used in `McpCaller`. `CloudEventProducer.buildCommonPostParam` selects its serializer from `getDataContentType()`, so publication fails when it is unset. The runtime also rejects a missing `subject`; `type` does not select the destination topic. Add `application/cloudevents+json` and the subscribed topic to all four builders. The suggestion fixes this client builder; use the client's subscribed response topic for the server builders.



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Re: [PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Posted by "Lyin-OTTF (via GitHub)" <gi...@apache.org>.

Lyin-OTTF commented on PR #5430:
URL: https://github.com/apache/eventmesh/pull/5430#issuecomment-6320892398

   The three workflows (Continuous Integration, License Check, Code Scanning) report "No jobs were run" on this PR and on #5431. None of them has path filters in `.github/workflows` (ci.yml triggers on `pull_request` for all branches), so this looks like the first-time-contributor approval gate rather than a skipped run.
   
   Could someone with write access approve the runs? Everything else is in place here: three approvals, and the Copilot findings are addressed in 82253de.


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Re: [PR] [ISSUE #5226] Fix A2A usage guide: replace non-public A2AProtocolTransportObject with CloudEvent publish (eventmesh)

Posted by "Lyin-OTTF (via GitHub)" <gi...@apache.org>.

Lyin-OTTF commented on PR #5430:
URL: https://github.com/apache/eventmesh/pull/5430#issuecomment-6344363676

   Thanks for the approvals. One heads-up: the workflows still have not run on this PR. The Actions runs are waiting on first-contributor approval, so there is no CI result to merge against yet. Could someone approve the workflow runs when convenient? The change is docs-only (two files under docs/a2a-protocol/), so I do not expect it to affect any build.


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