Class DeferredResult<T>

java.lang.Object
org.springframework.web.context.request.async.DeferredResult<T>
Type Parameters:
T - the result type
public class DeferredResult<T> extends Object
DeferredResult provides an alternative to using a Callable for asynchronous request processing. While a Callable is executed concurrently on behalf of the application, with a DeferredResult the application can produce the result from a thread of its choice.

Subclasses can extend this class to easily associate additional data or behavior with the DeferredResult. For example, one might want to associate the user used to create the DeferredResult by extending the class and adding an additional property for the user. In this way, the user could easily be accessed later without the need to use a data structure to do the mapping.

An example of associating additional behavior to this class might be realized by extending the class to implement an additional interface. For example, one might want to implement Comparable so that when the DeferredResult is added to a PriorityQueue it is handled in the correct order.

Since:
3.2
Author:
Rossen Stoyanchev, Juergen Hoeller, Rob Winch, Sam Brannen

  • Constructor Details

    • DeferredResult

      public DeferredResult()
      Create a DeferredResult.

    • DeferredResult

      public DeferredResult(@Nullable Long timeoutValue)
      Create a DeferredResult 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:
      timeoutValue - timeout value in milliseconds

    • DeferredResult

      public DeferredResult(@Nullable Long timeoutValue, Object timeoutResult)
      Create a DeferredResult with a timeout value and a default result to use in case of timeout.
      Parameters:
      timeoutValue - timeout value in milliseconds (ignored if null)
      timeoutResult - the result to use

    • DeferredResult

      public DeferredResult(@Nullable Long timeoutValue, Supplier<?> timeoutResult)
      Variant of DeferredResult(Long, Object) that accepts a dynamic fallback value based on a Supplier.
      Parameters:
      timeoutValue - timeout value in milliseconds (ignored if null)
      timeoutResult - the result supplier to use
      Since:
      5.1.1

  • Method Details

    • isSetOrExpired

      public final boolean isSetOrExpired()
      Return true if this DeferredResult is no longer usable either because it was previously set or because the underlying request expired.

      The result may have been set with a call to setResult(Object), or setErrorResult(Object), or as a result of a timeout, if a timeout result was provided to the constructor. The request may also expire due to a timeout or network error.

    • hasResult

      public boolean hasResult()
      Return true if the DeferredResult has been set.
      Since:
      4.0

    • getResult

      public @Nullable Object getResult()
      Return the result, or null if the result wasn't set. Since the result can also be null, it is recommended to use hasResult() first to check if there is a result prior to calling this method.
      Since:
      4.0

    • 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 before the DeferredResult has been populated. It may invoke setResult or setErrorResult to resume processing.

    • onError

      public void onError(Consumer<Throwable> callback)
      Register code to invoke when an error occurred during the async request.

      This method is called from a container thread when an error occurs while processing an async request before the DeferredResult has been populated. It may invoke setResult or setErrorResult to resume processing.

      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 is useful for detecting that a DeferredResult instance is no longer usable.

    • setResultHandler

      public final void setResultHandler(DeferredResult.DeferredResultHandler resultHandler)
      Provide a handler to use to handle the result value.
      Parameters:
      resultHandler - the handler
      See Also:

    • setResult

      public boolean setResult(@Nullable T result)
      Set the value for the DeferredResult and handle it.
      Parameters:
      result - the value to set
      Returns:
      true if the result was set and passed on for handling; false if the result was already set or the async request expired
      See Also:

    • setErrorResult

      public boolean setErrorResult(Object result)
      Set an error value for the DeferredResult and handle it. The value may be an Exception or Throwable in which case it will be processed as if a handler raised the exception.
      Parameters:
      result - the error result value
      Returns:
      true if the result was set to the error value and passed on for handling; false if the result was already set or the async request expired
      See Also: