I am using the Aries JAX-RS Whiteboard implementation that is using CXF internally.
I realized a behavior that does not match my expectation, so I checked the JAX-RS specification and IMHO the current behavior is wrong.
I opened an issue for Aires JAX-RS Whiteboard and have been told that it should be filled for CXF.
I could copy the whole initial description of the other issue to this one or link it (https://issues.apache.org/jira/browse/ARIES-1968)... I assume that all information should be added to the issue for the specific project, so I copy it:
The JAX-RS Specification 2.1 contains the chapter 9 for "Server-Sent Events".
The chapter 9.5 "Pipeline Processing" declares:
For compatibility purposes, implementations MUST initiate processing of an SSE response when either the first message is sent or when the resource method returns, whichever happens first. The initial SSE response, which may only include the HTTP headers, is processed using the standard JAX-RS pipeline as described in Appendix C. Each subsequent SSE event may include a different payload and thus require the use of a specific message body writer. Note that since this use case differs slightly from the normal JAX-RS pipeline, implementations SHOULD NOT call entity interceptors on each individual event (1).
So, the initial SSE response is processes using the standard JAX-RS pipeline (Appendix C).
Appendix C indicates that in front of the method invocation the "Container Request Chain" is handled and after the method invocation the "Container Response Chain" is handled.
The container response chain is currently not handled for the first response!
It is also not handled for the other reponses, but this is expected.
I checked v1.0.5, v1.0.6 and v1.0.7 all seems to be broken for me.
On a GET request to "http://127.0.0.1:8080/rest/foo/normal" is see (on the server console):
On a GET request to "http://127.0.0.1:8080/rest/foo/sse" is see (on the server console):
As the normal processing pipeline must be applied for the first SSE reponse I would expect "simple response filter" is shown once, too.
In my application there is a ContainerResponseFilter to allow (configurable) CORS. If it is enabled, the headers that allow the cross-origin access are added.
This needs to be added to the initial header (first response) of the SSE connection, too.