org.jgroups.util

Class Promise<T>

java.lang.Object

org.jgroups.util.Promise<T>

All Implemented Interfaces:

Condition

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

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 result. In order to block for a different result, reset() has to be called first.

Author:

Bela Ban

Field Summary

Fields

Modifier and Type	Field and Description
protected CondVar	cond
protected boolean	hasResult
protected java.util.concurrent.locks.Lock	lock
protected T	result

Constructor Summary

Constructors

Constructor and Description
Promise()

Method Summary

Modifier and Type	Method and Description
protected T	_getResultWithTimeout(long timeout) Blocks until a result is available, or timeout milliseconds have elapsed.
T	getResult()
T	getResult(long timeout) Returns the result, but never throws a TimeoutException; returns null instead.
T	getResult(long timeout, boolean reset)
T	getResultWithTimeout(long timeout) Blocks until a result is available, or timeout milliseconds have elapsed
T	getResultWithTimeout(long timeout, boolean reset)
boolean	hasResult() Checks whether result is available.
boolean	isMet() Return true if the condition is met and false otherwise
void	reset() Causes all waiting threads to return
void	reset(boolean signal)
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

Field Detail

lock

protected final java.util.concurrent.locks.Lock lock

cond

protected final CondVar cond

result

protected T result

hasResult

protected volatile boolean hasResult

Constructor Detail

Promise

public Promise()

Method Detail

isMet

public boolean isMet()

Description copied from interface: Condition

Return true if the condition is met and false otherwise

Specified by:

isMet in interface Condition

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)

getResultWithTimeout

public T getResultWithTimeout(long timeout,
                              boolean reset)
                       throws TimeoutException

Throws:

TimeoutException

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

getResult

public T getResult(long timeout,
                   boolean reset)

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

reset

public void reset(boolean signal)

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)