DeferredResult (Spring Framework 4.0.4.RELEASE API)

java.lang.Object
- org.springframework.web.context.request.async.DeferredResult<T>

```
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, Rob Winch

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static interface DeferredResult.DeferredResultHandler
Handles a DeferredResult value when set.

Nested Classes
Modifier and Type	Class and Description
`static interface`	`DeferredResult.DeferredResultHandler` Handles a DeferredResult value when set.

Constructor Summary

Constructors
Constructor and Description
`DeferredResult()` Create a DeferredResult.
`DeferredResult(long timeout)` Create a DeferredResult with a timeout value.
`DeferredResult(Long timeout, Object timeoutResult)` Create a DeferredResult with a timeout value and a default result to use in case of timeout.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Object`	`getResult()`
`boolean`	`hasResult()`
`boolean`	`isSetOrExpired()` Return `true` if this DeferredResult is no longer usable either because it was previously set or because the underlying request expired.
`void`	`onCompletion(Runnable callback)` Register code to invoke when the async request completes.
`void`	`onTimeout(Runnable callback)` Register code to invoke when the async request times out.
`boolean`	`setErrorResult(Object result)` Set an error value for the `DeferredResult` and handle it.
`boolean`	`setResult(T result)` Set the value for the DeferredResult and handle it.
`void`	`setResultHandler(DeferredResult.DeferredResultHandler resultHandler)` Provide a handler to use to handle the result value.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DeferredResult
```
public DeferredResult()
```
    Create a DeferredResult.
  - DeferredResult
```
public DeferredResult(long timeout)
```
    Create a DeferredResult with a timeout value.
    
    Parameters:
    
    timeout - timeout value in milliseconds
  - DeferredResult
```
public DeferredResult(Long timeout,
                      Object timeoutResult)
```
    Create a DeferredResult with a timeout value and a default result to use in case of timeout.
    
    Parameters:
    
    timeout - timeout value in milliseconds; ignored if null
    
    timeoutResult - the result to use
- Method Detail
  - 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()
```
    Returns:
    
    true if the DeferredResult has been set.
  - getResult
```
public Object getResult()
```
    Returns:
    
    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.
  - 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 set. It may invoke setResult or setErrorResult to resume processing.
  - 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 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:
    
    DeferredResultProcessingInterceptor
  - setResult
```
public boolean setResult(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:
    
    isSetOrExpired()
  - 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:
    
    isSetOrExpired()

Class DeferredResult<T>

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DeferredResult

DeferredResult

DeferredResult

Method Detail

isSetOrExpired

hasResult

getResult

onTimeout

onCompletion

setResultHandler

setResult

setErrorResult