Package javax.ws.rs.container

Interface AsyncResponse

  • public interface AsyncResponse
    An injectable and asynchronous response that provides means for asynchronous server side response processing.

    A new instance of AsyncResponse may be injected into a resource or sub-resource method parameter using the @Suspended annotation.

    Each asynchronous response instance is bound to the running request and can be used to asynchronously provide the request processing result or otherwise manipulate the suspended client connection. The available operations include:
    • updating suspended state data (time-out value, response ...)
    • resuming the suspended request processing
    • canceling the suspended request processing

    Following example demonstrates the use of the AsyncResponse for asynchronous HTTP request processing: 

     @Path("/messages/next")
 public class MessagingResource {
     private static final BlockingQueue<AsyncResponse> suspended =
             new ArrayBlockingQueue<AsyncResponse>(5);

     @GET
     public void readMessage(@Suspended AsyncResponse ar) throws InterruptedException {
         suspended.put(ar);
     }

     @POST
     public String postMessage(final String message) throws InterruptedException {
         final AsyncResponse ar = suspended.take();
         ar.resume(message); // resumes the processing of one GET request
         return "Message sent";
     }
 }

    If the asynchronous response was suspended with a positive timeout value, and has not been explicitly resumed before the timeout has expired, the processing will be resumed once the specified timeout threshold is reached, provided a positive timeout value was set on the response.

    By default a timed-out asynchronous response is resumed with a WebApplicationException that has HTTP 503 (Service unavailable) error response status code set. This default behavior may be overridden by setting a custom time-out handler.

    Since:
    2.0
    Author:
    Marek Potociar

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static long NO_TIMEOUT
      Constant specifying no suspend timeout value.

    • Method Summary

      Modifier and Type Method Description
      boolean cancel()
      Cancel the suspended request processing.
      boolean cancel​(int retryAfter)
      Cancel the suspended request processing.
      boolean cancel​(Date retryAfter)
      Cancel the suspended request processing.
      boolean isCancelled()
      Check if the asynchronous response instance has been cancelled.
      boolean isDone()
      Check if the processing of a request this asynchronous response instance belongs to has finished.
      boolean isSuspended()
      Check if the asynchronous response instance is in a suspended state.
      Collection<Class<?>> register​(Class<?> callback)
      Register an asynchronous processing lifecycle callback class to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
      Map<Class<?>,​Collection<Class<?>>> register​(Class<?> callback, Class<?>... callbacks)
      Register asynchronous processing lifecycle callback classes to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
      Collection<Class<?>> register​(Object callback)
      Register an asynchronous processing lifecycle callback instance to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
      Map<Class<?>,​Collection<Class<?>>> register​(Object callback, Object... callbacks)
      Register an asynchronous processing lifecycle callback instances to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
      boolean resume​(Object response)
      Resume the suspended request processing using the provided response data.
      boolean resume​(Throwable response)
      Resume the suspended request processing using the provided throwable.
      boolean setTimeout​(long time, TimeUnit unit)
      Set/update the suspend timeout.
      void setTimeoutHandler​(TimeoutHandler handler)
      Set/replace a time-out handler for the suspended asynchronous response.

    • Field Detail

      • NO_TIMEOUT

        static final long NO_TIMEOUT
        Constant specifying no suspend timeout value.
        See Also:
        Constant Field Values

    • Method Detail

      • resume

        boolean resume​(Object response)
        Resume the suspended request processing using the provided response data. The provided response data can be of any Java type that can be returned from a Resource method.

        The asynchronous response must be still in a suspended state for this method to succeed.

        By executing this method, the request is guaranteed to complete either successfully or with an error. The data processing by the runtime follows the same path as it would for the response data returned synchronously by a resource, except that unmapped exceptions are not re-thrown by the runtime to be handled by a hosting I/O container. Instead, any unmapped exceptions are propagated to the hosting I/O container via a container-specific callback mechanism. Depending on the container implementation, propagated unmapped exceptions typically result in an error status being sent to the client and/or the connection being closed.

        Parameters:
        response - data to be sent back in response to the suspended request.
        Returns:
        true if the request processing has been resumed, returns false in case the request processing is not suspended and could not be resumed.
        See Also:
        resume(Throwable)

      • resume

        boolean resume​(Throwable response)
        Resume the suspended request processing using the provided throwable. For the provided throwable same rules apply as for an exception thrown by a Resource method.

        By executing this method, the request is guaranteed to complete either successfully or with an error. The throwable processing by the runtime follows the same path as it would for the response data returned synchronously by a resource, except that unmapped exceptions are not re-thrown by the runtime to be handled by a hosting I/O container. Instead, any unmapped exceptions are propagated to the hosting I/O container via a container-specific callback mechanism. Depending on the container implementation, propagated unmapped exceptions typically result in an error status being sent to the client and/or the connection being closed.

        Parameters:
        response - an exception to be raised in response to the suspended request.
        Returns:
        true if the response has been resumed, returns false in case the response is not suspended and could not be resumed.
        See Also:
        resume(Object)

      • cancel

        boolean cancel()
        Cancel the suspended request processing.

        When a request processing is cancelled using this method, the API implementation MUST indicate to the client that the request processing has been cancelled by sending back a HTTP 503 (Service unavailable) error response.

        Invoking a cancel(...) method multiple times to cancel request processing has the same effect as canceling the request processing only once. Invoking a cancel(...) method on an asynchronous response instance that has already been cancelled or resumed has no effect and the method call is ignored while returning true, in case the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a resume(...) method) or resumed due to a time-out, method returns false.

        Returns:
        true if the request processing has been cancelled, returns false in case the request processing is not suspended and could not be cancelled and is not cancelled already.
        See Also:
        cancel(int), cancel(java.util.Date)

      • cancel

        boolean cancel​(int retryAfter)
        Cancel the suspended request processing.

        When a request processing is cancelled using this method, the API implementation MUST indicate to the client that the request processing has been cancelled by sending back a HTTP 503 (Service unavailable) error response with a Retry-After header set to the value provided by the method parameter.

        Invoking a cancel(...) method multiple times to cancel request processing has the same effect as canceling the request processing only once. Invoking a cancel(...) method on an asynchronous response instance that has already been cancelled or resumed has no effect and the method call is ignored while returning true, in case the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a resume(...) method) or resumed due to a time-out, method returns false.

        Parameters:
        retryAfter - a decimal integer number of seconds after the response is sent to the client that indicates how long the service is expected to be unavailable to the requesting client.
        Returns:
        true if the request processing has been cancelled, returns false in case the request processing is not suspended and could not be cancelled and is not cancelled already.
        See Also:
        cancel(), cancel(java.util.Date)

      • cancel

        boolean cancel​(Date retryAfter)
        Cancel the suspended request processing.

        When a request processing is cancelled using this method, the API implementation MUST indicate to the client that the request processing has been cancelled by sending back a HTTP 503 (Service unavailable) error response with a Retry-After header set to the value provided by the method parameter.

        Invoking a cancel(...) method multiple times to cancel request processing has the same effect as canceling the request processing only once. Invoking a cancel(...) method on an asynchronous response instance that has already been cancelled or resumed has no effect and the method call is ignored while returning true, in case the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a resume(...) method) or resumed due to a time-out, method returns false.

        Parameters:
        retryAfter - a date that indicates how long the service is expected to be unavailable to the requesting client.
        Returns:
        true if the request processing has been cancelled, returns false in case the request processing is not suspended and could not be cancelled and is not cancelled already.
        See Also:
        cancel(), cancel(int)

      • isSuspended

        boolean isSuspended()
        Check if the asynchronous response instance is in a suspended state. Method returns true if this asynchronous response is still suspended and has not finished processing yet (either by resuming or canceling the response).
        Returns:
        true if this asynchronous response is in a suspend state, false otherwise.
        See Also:
        isCancelled(), isDone()

      • isCancelled

        boolean isCancelled()
        Check if the asynchronous response instance has been cancelled. Method returns true if this asynchronous response has been canceled before completion.
        Returns:
        true if this task was canceled before completion.
        See Also:
        isSuspended(), isDone()

      • isDone

        boolean isDone()
        Check if the processing of a request this asynchronous response instance belongs to has finished. Method returns true if the processing of a request this asynchronous response is bound to is finished.

        The request processing may be finished due to a normal termination, a suspend timeout, or cancellation -- in all of these cases, this method will return true.

        Returns:
        true if this execution context has finished processing.
        See Also:
        isSuspended(), isCancelled()

      • setTimeout

        boolean setTimeout​(long time,
                   TimeUnit unit)
        Set/update the suspend timeout.

        The new suspend timeout values override any timeout value previously specified. The asynchronous response must be still in a suspended state for this method to succeed.

        Parameters:
        time - suspend timeout value in the give time unit. Value lower or equal to 0 causes the context to suspend indefinitely.
        unit - suspend timeout value time unit.
        Returns:
        true if the suspend time out has been set, returns false in case the request processing is not in the suspended state.

      • setTimeoutHandler

        void setTimeoutHandler​(TimeoutHandler handler)
        Set/replace a time-out handler for the suspended asynchronous response.

        The time-out handler will be invoked when the suspend period of this asynchronous response times out. The job of the time-out handler is to resolve the time-out situation by either

        • resuming the suspended response
        • cancelling the suspended response
        • extending the suspend period by setting a new suspend time-out

        Note that in case the response is suspended indefinitely, the time-out handler may never be invoked.

        Parameters:
        handler - response time-out handler.

      • register

        Collection<Class<?>> register​(Class<?> callback)
        Register an asynchronous processing lifecycle callback class to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
        Parameters:
        callback - callback class.
        Returns:
        collection of registered callback interfaces. If the callback class does not implement any recognized callback interfaces, the returned collection will be empty.
        Throws:
        NullPointerException - in case the callback class is null.

      • register

        Map<Class<?>,​Collection<Class<?>>> register​(Class<?> callback,
                                                  Class<?>... callbacks)
        Register asynchronous processing lifecycle callback classes to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
        Parameters:
        callback - callback class.
        callbacks - additional callback classes.
        Returns:
        map of registered classes and the callback interfaces registered for each class. If a callback class does not implement any recognized callback interfaces, the associated collection of registered interfaces for the class will be empty.
        Throws:
        NullPointerException - in case any of the callback classes is null.

      • register

        Collection<Class<?>> register​(Object callback)
        Register an asynchronous processing lifecycle callback instance to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
        Parameters:
        callback - callback instance implementing one or more of the recognized callback interfaces.
        Returns:
        collection of registered callback interfaces. If the callback class does not implement any recognized callback interfaces, the returned collection will be empty.
        Throws:
        NullPointerException - in case the callback instance is null.

      • register

        Map<Class<?>,​Collection<Class<?>>> register​(Object callback,
                                                  Object... callbacks)
        Register an asynchronous processing lifecycle callback instances to receive lifecycle events for the asynchronous response based on the implemented callback interfaces.
        Parameters:
        callback - callback instance.
        callbacks - additional callback instances.
        Returns:
        map of registered classes and the callback interfaces registered for each class. If a callback class does not implement any recognized callback interfaces, the associated collection of registered interfaces for the class will be empty.
        Throws:
        NullPointerException - in case any of the callback instances is null.