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package org.glassfish.grizzly.utils;
import java.util.Collection;
import org.glassfish.grizzly.CompletionHandler;
import org.glassfish.grizzly.Grizzly;
import org.glassfish.grizzly.impl.FutureImpl;
import org.glassfish.grizzly.impl.ReadyFutureImpl;
import org.glassfish.grizzly.impl.SafeFutureImpl;
import org.glassfish.grizzly.utils.conditions.Condition;
import java.util.Iterator;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Future;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.glassfish.grizzly.localization.LogMessages;
/**
* Class, which holds the state.
* Provides API for state change notification, state read/write access locking.
*
* @author Alexey Stashok
*/
public final class StateHolder<E> {
private static final Logger _logger = Grizzly.logger(StateHolder.class);
private volatile E state;
private final ReentrantReadWriteLock readWriteLock;
private final Collection<ConditionElement<E>> conditionListeners;
/**
* Constructs <code>StateHolder</code>.
*/
public StateHolder() {
this(null);
}
/**
* Constructs <code>StateHolder</code>.
*/
public StateHolder(E initialState) {
state = initialState;
readWriteLock = new ReentrantReadWriteLock();
conditionListeners = new ConcurrentLinkedQueue<ConditionElement<E>>();
}
/**
* Gets current state
* Current StateHolder locking mode will be used
* @return state
*/
public E getState() {
return state;
}
/**
* Sets current state
* Current StateHolder locking mode will be used
* @param state
*/
public void setState(E state) {
readWriteLock.writeLock().lock();
try {
this.state = state;
// downgrading lock to read
readWriteLock.readLock().lock();
readWriteLock.writeLock().unlock();
notifyConditionListeners();
} finally {
readWriteLock.readLock().unlock();
}
}
/**
* Gets Read/Write locker, which is used by this <code>StateHolder</code>
* @return locker
*/
public ReentrantReadWriteLock getStateLocker() {
return readWriteLock;
}
/**
* 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
* <code>StateHolder</code>'s listener set.
* @param state State, listener is interested in
* @param completionHandler that will be notified. This <code>StateHolder</code>
* implementation works with Runnable, Callable, CountDownLatch, Object
* listeners
* @return <code>ConditionListener</code>, 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 Future<E> notifyWhenStateIsEqual(final E state,
final CompletionHandler<E> completionHandler) {
return notifyWhenConditionMatchState(new Condition() {
@Override
public boolean check() {
return state == StateHolder.this.state;
}
}, completionHandler);
}
/**
* 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 <code>StateHolder</code>'s listener set.
* @param state State, listener is interested in
* @param completionHandler that will be notified. This <code>StateHolder</code>
* implementation works with Runnable, Callable, CountDownLatch, Object
* listeners
* @return <code>ConditionListener</code>, 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 Future<E> notifyWhenStateIsNotEqual(final E state,
final CompletionHandler<E> completionHandler) {
return notifyWhenConditionMatchState(new Condition() {
@Override
public boolean check() {
return state != StateHolder.this.state;
}
}, completionHandler);
}
/**
* Register listener, which will be notified, when state will match the condition.
* Once listener will be notified - it will be removed from this
* <code>StateHolder</code>'s listener set.
* @param condition Condition, the listener is interested in
* @param completionHandler that will be notified. This <code>StateHolder</code>
* implementation works with Runnable, Callable, CountDownLatch, Object
* listeners
* @return <code>ConditionListener</code>, if current state doesn't match the condition
* and listener was registered, null if current state matches the condition.
* In both cases listener will be notified
*/
public Future<E> notifyWhenConditionMatchState(Condition condition,
CompletionHandler<E> completionHandler) {
Future<E> resultFuture;
readWriteLock.readLock().lock();
try {
if (condition.check()) {
if (completionHandler != null) {
completionHandler.completed(state);
}
resultFuture = ReadyFutureImpl.create(state);
} else {
final FutureImpl<E> future = SafeFutureImpl.create();
final ConditionElement<E> elem =
new ConditionElement<E>(condition, future, completionHandler);
conditionListeners.add(elem);
resultFuture = future;
}
} finally {
readWriteLock.readLock().unlock();
}
return resultFuture;
}
protected void notifyConditionListeners() {
Iterator<ConditionElement<E>> it = conditionListeners.iterator();
while(it.hasNext()) {
ConditionElement<E> element = it.next();
try {
if (element.condition.check()) {
it.remove();
if (element.completionHandler != null) {
element.completionHandler.completed(state);
}
element.future.result(state);
}
} catch(Exception e) {
_logger.log(Level.WARNING,
LogMessages.WARNING_GRIZZLY_STATE_HOLDER_CALLING_CONDITIONLISTENER_EXCEPTION(),
e);
}
}
}
protected static final class ConditionElement<E> {
private final Condition condition;
private final FutureImpl<E> future;
private final CompletionHandler<E> completionHandler;
public ConditionElement(Condition condition, FutureImpl<E> future,
CompletionHandler<E> completionHandler) {
this.condition = condition;
this.future = future;
this.completionHandler = completionHandler;
}
public CompletionHandler<E> getCompletionHandler() {
return completionHandler;
}
public Condition getCondition() {
return condition;
}
public FutureImpl<E> getFuture() {
return future;
}
}
}