Class ResponseBodyEmitter

java.lang.Object
org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter
Direct Known Subclasses:
SseEmitter
public class ResponseBodyEmitter extends Object
A controller method return value type for asynchronous request processing where one or more objects are written to the response.

While DeferredResult is used to produce a single result, a ResponseBodyEmitter can be used to send multiple objects where each object is written with a compatible HttpMessageConverter.

Supported as a return type on its own as well as within a ResponseEntity. 

@RequestMapping(value="/stream", method=RequestMethod.GET)
public ResponseBodyEmitter handle() {
           ResponseBodyEmitter emitter = new ResponseBodyEmitter();
           // Pass the emitter to another component...
           return emitter;
}

// in another thread
emitter.send(foo1);

// and again
emitter.send(foo2);

// and done
emitter.complete();
Since:
4.2
Author:
Rossen Stoyanchev, Juergen Hoeller, Brian Clozel, Taeik Lim

  • Field Details

    • writeLock

      protected final Lock writeLock
      Guards access to write operations on the response.

  • Constructor Details

    • ResponseBodyEmitter

      public ResponseBodyEmitter()
      Create a new ResponseBodyEmitter instance.

    • ResponseBodyEmitter

      public ResponseBodyEmitter(Long timeout)
      Create a ResponseBodyEmitter with a custom timeout value.

      By default not set in which case the default configured in the MVC Java Config or the MVC namespace is used, or if that's not set, then the timeout depends on the default of the underlying server.

      Parameters:
      timeout - the timeout value in milliseconds

  • Method Details

    • getTimeout

      public @Nullable Long getTimeout()
      Return the configured timeout value, if any.

    • extendResponse

      protected void extendResponse(ServerHttpResponse outputMessage)
      Invoked after the response is updated with the status code and headers, if the ResponseBodyEmitter is wrapped in a ResponseEntity, but before the response is committed, i.e. before the response body has been written to.

      The default implementation is empty.

    • send

      public void send(Object object) throws IOException
      Write the given object to the response.

      If any exception occurs a dispatch is made back to the app server where Spring MVC will pass the exception through its exception handling mechanism.

      Note: if the send fails with an IOException, you do not need to call completeWithError(Throwable) in order to clean up. Instead the Servlet container creates a notification that results in a dispatch where Spring MVC invokes exception resolvers and completes processing.

      Parameters:
      object - the object to write
      Throws:
      IOException - raised when an I/O error occurs
      IllegalStateException - wraps any other errors

    • send

      public void send(Object object, @Nullable MediaType mediaType) throws IOException
      Overloaded variant of send(Object) that also accepts a MediaType hint for how to serialize the given Object.
      Parameters:
      object - the object to write
      mediaType - a MediaType hint for selecting an HttpMessageConverter
      Throws:
      IOException - raised when an I/O error occurs
      IllegalStateException - wraps any other errors

    • send

      public void send(Set<ResponseBodyEmitter.DataWithMediaType> items) throws IOException
      Write a set of data and MediaType pairs in a batch.

      Compared to send(Object, MediaType), this batches the write operations and flushes to the network at the end.

      Parameters:
      items - the object and media type pairs to write
      Throws:
      IOException - raised when an I/O error occurs
      IllegalStateException - wraps any other errors
      Since:
      6.0.12

    • complete

      public void complete()
      Complete request processing by performing a dispatch into the servlet container, where Spring MVC is invoked once more, and completes the request processing lifecycle.

      Note: this method should be called by the application to complete request processing. It should not be used after container related events such as an error while sending.

    • completeWithError

      public void completeWithError(Throwable ex)
      Complete request processing with an error.

      A dispatch is made into the app server where Spring MVC will pass the exception through its exception handling mechanism. Note however that at this stage of request processing, the response is committed and the response status can no longer be changed.

      Note: this method should be called by the application to complete request processing with an error. It should not be used after container related events such as an error while sending.

    • onTimeout

      public void onTimeout(Runnable callback)
      Register code to invoke when the async request times out. This method is called from a container thread when an async request times out.

      As of 6.2, one can register multiple callbacks for this event.

    • onError

      public void onError(Consumer<Throwable> callback)
      Register code to invoke for an error during async request processing. This method is called from a container thread when an error occurred while processing an async request.

      As of 6.2, one can register multiple callbacks for this event.

      Since:
      5.0

    • onCompletion

      public void onCompletion(Runnable callback)
      Register code to invoke when the async request completes. This method is called from a container thread when an async request completed for any reason including timeout and network error. This method is useful for detecting that a ResponseBodyEmitter instance is no longer usable.

      As of 6.2, one can register multiple callbacks for this event.

    • toString

      public String toString()
      Overrides:
      toString in class Object