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*
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*
* Copyright 2007-2008 Sun Microsystems, Inc. All rights reserved.
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* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
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* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
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package com.sun.grizzly.util;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Level;
/**
* Class, which holds the state.
* Provides API for state change notification, state read/write access locking.
*
* @author Alexey Stashok
*/
public class StateHolder {
private AtomicReference stateRef;
private ReentrantReadWriteLock readWriteLock;
private volatile boolean isLockEnabled;
private Map, Object> conditionListeners;
/**
* Constructs {@link StateHolder}.
* StateHolder will work in not-locking mode.
*/
public StateHolder() {
this(false);
}
/**
* Constructs {@link StateHolder}.
* @param isLockEnabled locking mode
*/
public StateHolder(boolean isLockEnabled) {
stateRef = new AtomicReference();
readWriteLock = new ReentrantReadWriteLock();
conditionListeners = new ConcurrentHashMap, Object>();
this.isLockEnabled = isLockEnabled;
}
/**
* Gets current state
* Current StateHolder locking mode will be used
* @return state
*/
public E getState() {
return getState(isLockEnabled);
}
/**
* Gets current state
* @param locked if true, get will be invoked in locking mode, false - non-locked
* @return state
*/
public E getState(boolean locked) {
if (locked) {
readWriteLock.readLock().lock();
}
E retState = stateRef.get();
if (locked) {
readWriteLock.readLock().unlock();
}
return retState;
}
/**
* Sets current state
* Current StateHolder locking mode will be used
* @param state
*/
public void setState(E state) {
setState(state, isLockEnabled);
}
/**
* Sets current state
* @param state
* @param locked if true, set will be invoked in locking mode, false - non-locking
*/
public void setState(E state, boolean locked) {
if (locked) {
readWriteLock.writeLock().lock();
}
stateRef.set(state);
// downgrading lock to read
if (locked) {
readWriteLock.readLock().lock();
readWriteLock.writeLock().unlock();
}
checkConditionListeners(state);
if (locked) {
readWriteLock.readLock().unlock();
}
}
/**
* Gets Read/Write locker, which is used by this {@link StateHolder}
* @return locker
*/
public ReentrantReadWriteLock getStateLocker() {
return readWriteLock;
}
/**
* Gets current locking mode
* @return true, if mode is set to locking, false otherwise
*/
public boolean isLockEnabled() {
return isLockEnabled;
}
/**
* Setss current locking mode
* @param isLockEnabled true, if mode will be set to locking, false otherwise
*/
public void setLockEnabled(boolean isLockEnabled) {
this.isLockEnabled = isLockEnabled;
}
/**
* Register listener, which will be notified, when state will be equal to passed
* one. Once listener will be notified - it will be removed from this
* {@link StateHolder}'s listener set.
* @param state State, listener is interested in
* @param listener Object, which will be notified. This {@link StateHolder}
* implementation works with Runnable, Callable, CountDownLatch, Object
* listeners
* @return ConditionListener, if current state is not equal to required
* and listener was registered, null if current state is equal to required.
* In both cases listener will be notified
*/
public ConditionListener notifyWhenStateIsEqual(E state, Object listener) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
ConditionListener conditionListener = null;
if (stateRef.get().equals(state)) {
EventListener.notifyListener(listener);
} else {
conditionListener = new EqualConditionListener();
EventListener eventListener = new EventListener();
eventListener.set(listener);
conditionListener.set(state, eventListener);
conditionListeners.put(conditionListener, this);
}
if (isLockEnabledLocal) {
getStateLocker().writeLock().unlock();
}
return conditionListener;
}
/**
* Register listener, which will be notified, when state will become not equal
* to passed one. Once listener will be notified - it will be removed from
* this {@link StateHolder}'s listener set.
* @param state State, listener is interested in
* @param listener Object, which will be notified. This {@link StateHolder}
* implementation works with Runnable, Callable, CountDownLatch, Object
* listeners
* @return ConditionListener, if current state is equal to required
* and listener was registered, null if current state is not equal to required.
* In both cases listener will be notified
*/
public ConditionListener notifyWhenStateIsNotEqual(E state, Object listener) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
ConditionListener conditionListener = null;
if (!stateRef.get().equals(state)) {
EventListener.notifyListener(listener);
} else {
conditionListener = new NotEqualConditionListener();
EventListener eventListener = new EventListener();
eventListener.set(listener);
conditionListener.set(state, eventListener);
conditionListeners.put(conditionListener, this);
}
if (isLockEnabledLocal) {
getStateLocker().writeLock().unlock();
}
return conditionListener;
}
/**
* Register custom condition listener, which will be notified, when listener's
* condition will become true. Once listener will be notified - it will be
* removed from this {@link StateHolder}'s listener set.
* @param conditionListener contains both condition and listener, which will be
* called, when condition become true
*/
public void notifyWhenConditionMatchState(ConditionListener conditionListener) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
E currentState = getState();
if (conditionListener.check(currentState)) {
conditionListener.notifyListener();
} else {
conditionListeners.put(conditionListener, this);
}
if (isLockEnabledLocal) {
getStateLocker().writeLock().unlock();
}
}
public void removeConditionListener(ConditionListener conditionListener) {
if (conditionListener == null) return;
conditionListeners.remove(conditionListener);
}
protected void checkConditionListeners(E state) {
Iterator> it = conditionListeners.keySet().iterator();
while(it.hasNext()) {
ConditionListener listener = it.next();
try {
if (listener.check(state)) {
it.remove();
listener.notifyListener();
}
} catch(Exception e) {
LoggerUtils.getLogger().log(Level.WARNING, "Error calling ConditionListener", e);
}
}
}
/**
* Common ConditionListener class, which could be used with StateHolder, to
* register custom conditions.
*
* On each state change - condition will be checked, if it's true - Condition's
* listener will be notified.
*/
public static abstract class ConditionListener {
public E state;
public EventListener listener;
protected void set(E state, EventListener listener) {
this.state = state;
this.listener = listener;
}
public void notifyListener() {
listener.notifyEvent();
}
public abstract boolean check(E state);
}
/**
* Equal ConditionListener implementation
* @param E state class
*/
public static class EqualConditionListener extends ConditionListener {
public boolean check(E state) {
return state.equals(this.state);
}
}
/**
* Not equal ConditionListener implementation
* @param E state class
*/
public static class NotEqualConditionListener extends ConditionListener {
public boolean check(E state) {
return !state.equals(this.state);
}
}
/**
* EventListener class, which is a part of
* EventConditionListener, and implements notificatation logic,
* when condition becomes true.
*/
public static class EventListener {
public Object notificationObject;
public void set(Object notificationObject) {
this.notificationObject = notificationObject;
}
public void notifyEvent() {
notifyListener(notificationObject);
}
protected static void notifyListener(Object listener) {
if (listener instanceof CountDownLatch) {
((CountDownLatch) listener).countDown();
} else if (listener instanceof Callable) {
try {
((Callable) listener).call();
} catch(Exception e) {
throw new RuntimeException(e);
}
} else if (listener instanceof Runnable) {
((Runnable) listener).run();
} else {
synchronized(listener) {
listener.notify();
}
}
}
}
}
