org.jgroups.util
Class Promise<T>

java.lang.Object
  org.jgroups.util.Promise<T>

public class Promise<T>
extends java.lang.Object

Allows a thread to submit an asynchronous request and to wait for the result. The caller may choose to check for the result at a later time, or immediately and it may block or not. Both the caller and responder have to know the promise.

When the result is available, hasResult() will always return true and getResult() will return the same result. In order to block for a different result, reset() has to be called first.

Author:

Bela Ban

Constructor Summary

Promise()

Method Summary

protected T	_getResultWithTimeout(long timeout) Blocks until a result is available, or timeout milliseconds have elapsed.
java.util.concurrent.locks.Condition	getCond()
java.util.concurrent.locks.Lock	getLock()
T	getResult()
T	getResult(long timeout) Returns the result, but never throws a TimeoutException; returns null instead.
T	getResultWithTimeout(long timeout) Blocks until a result is available, or timeout milliseconds have elapsed
boolean	hasResult() Checks whether result is available.
void	reset() Causes all waiting threads to return
void	setResult(T obj) Sets the result and notifies any threads waiting for it
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Promise

public Promise()

Method Detail

getLock

public java.util.concurrent.locks.Lock getLock()

getCond

public java.util.concurrent.locks.Condition getCond()

getResultWithTimeout

public T getResultWithTimeout(long timeout)
                       throws TimeoutException

Blocks until a result is available, or timeout milliseconds have elapsed

Parameters:

timeout - in ms

Returns:

An object

Throws:

TimeoutException - If a timeout occurred (implies that timeout > 0)

getResult

public T getResult()

getResult

public T getResult(long timeout)

Returns the result, but never throws a TimeoutException; returns null instead.

Parameters:

timeout - in ms

Returns:

T

hasResult

public boolean hasResult()

Checks whether result is available. Does not block.

setResult

public void setResult(T obj)

Sets the result and notifies any threads waiting for it

reset

public void reset()

Causes all waiting threads to return

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

_getResultWithTimeout

protected T _getResultWithTimeout(long timeout)
                           throws TimeoutException

Blocks until a result is available, or timeout milliseconds have elapsed. Needs to be called with lock held

Parameters:

timeout - in ms

Returns:

An object

Throws:

TimeoutException - If a timeout occurred (implies that timeout > 0)