Package org.springframework.web.servlet.mvc.method.annotation

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

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ResponseBodyEmitter.DataWithMediaType	A simple holder of data to be written along with a MediaType hint for selecting a message converter to write with.

Constructor Summary

Constructors

Constructor	Description
ResponseBodyEmitter()	Create a new ResponseBodyEmitter instance.
ResponseBodyEmitter(Long timeout)	Create a ResponseBodyEmitter with a custom timeout value.

Method Summary

Modifier and Type	Method	Description
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.
void	completeWithError(Throwable ex)	Complete request processing with an error.
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.
Long	getTimeout()	Return the configured timeout value, if any.
void	onCompletion(Runnable callback)	Register code to invoke when the async request completes.
void	onError(Consumer<Throwable> callback)	Register code to invoke for an error during async request processing.
void	onTimeout(Runnable callback)	Register code to invoke when the async request times out.
void	send(Object object)	Write the given object to the response.
void	send(Object object, MediaType mediaType)	Overloaded variant of send(Object) that also accepts a MediaType hint for how to serialize the given Object.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

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

@Nullable
public 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

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.

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.

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.

toString

public String toString()

Overrides:

toString in class Object