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Spring Causes SseEmitter Cannot redirect after response has been posted

For a simple controller with this way:

@RequestMapping(method = RequestMethod.GET, value = "{id}/update")
public ResponseEntity<SseEmitter>  update() throws IOException {
    final SseEmitter  sseEmitter = new SseEmitter();

    return ResponseEntity.ok(sseEmitter);
}

I tried this too:

@RequestMapping(method = RequestMethod.GET, value = "{id}/update")
public SseEmitter  update() throws IOException {
    final SseEmitter  sseEmitter = new SseEmitter();

    return sseEmitter;
}

But both Tomcat 8.0.21 methods throw the above exception 30 seconds after the request is issued. What's going on under the hood?

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2 answers


This could be the default asynchronous timeout of your servlet container. You can change the default with Spring:



@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
        configurer.setDefaultTimeout(1000000);
    }

}
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You can set a timeout for the SseEmitter in your constructor:

final SseEmitter sseEmitter = new SseEmitter(60000L); // Timeout in millis


The client will automatically connect, but by default it will wait 2-3 seconds. You can override this when sending messages:

// Instruct the client to reconnect after 500ms
emitter.send(SseEmitter.event().reconnectTime(500).data(message));
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