ResponseBodyEmitter skips same messages during initialization [SPR-13223]

[spring-projects-issues]

Tomasz Nurkiewicz opened SPR-13223 and commented

When the same message is sent via ResponseBodyEmitter before initialization, subsequent messages are dropped because uses ResponseBodyEmitter#initHandlerCache map keys to store events.

Problematic code (using SseEmitter):

@RequestMapping("/sse")
public SseEmitter sse() throws IOException, InterruptedException {
	final SseEmitter emitter = new SseEmitter();
	emitter.send("A");
	emitter.send("B");
	emitter.send("C");
	emitter.complete();
	return emitter;
}

The response is:

data:A

BC

while it should be:

data:A

data:B

data:C

The reason is that both data: and \n\n are dropped as duplicates. Pull request with test case and fix comes shortly.

---

Affects: 4.2 RC2

Issue Links:

• SseEmitter is not thread safe [SPR-13224] #17815 SseEmitter is not thread safe

Referenced from: commits bdb6348

[spring-projects-issues]

Tomasz Nurkiewicz commented

PR: #837

[spring-projects-issues]

Juergen Hoeller commented

Implemented together with #17815, using a common struct for a value with media type both in ResponseBodyEmitter and in SseEventBuilder, and using common synchronization for all affected operations - including the option to manually synchronize on the emitter, for aggregating multiple values just like SseEmitter does by default now.

Juergen