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package org.glassfish.grizzly.util;
import org.glassfish.grizzly.util.conditions.DefaultConditionListener;
import org.glassfish.grizzly.util.conditions.ConditionListener;
import org.glassfish.grizzly.Grizzly;
import org.glassfish.grizzly.util.conditions.Condition;
import org.glassfish.grizzly.util.conditions.EqualCondition;
import org.glassfish.grizzly.util.conditions.NotEqualCondition;
import org.glassfish.grizzly.util.conditions.OneTimeConditionListener;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Class, which holds the state.
* Provides API for state change notification, state read/write access locking.
*
* @author Alexey Stashok
*/
public class StateHolder {
private static Logger _logger = Grizzly.logger;
private volatile E state;
private final ReentrantReadWriteLock readWriteLock;
private final boolean isLockEnabled;
private Collection> conditionListeners;
/**
* Constructs StateHolder.
* StateHolder will work in not-locking mode.
*/
public StateHolder() {
this(false);
}
/**
* Constructs StateHolder.
* @param isLockEnabled locking mode
*/
public StateHolder(boolean isLockEnabled) {
readWriteLock = new ReentrantReadWriteLock();
conditionListeners = new LinkedTransferQueue>();
this.isLockEnabled = isLockEnabled;
}
/**
* Constructs StateHolder.
* @param isLockEnabled locking mode
*/
public StateHolder(boolean isLockEnabled, E initialState) {
state = initialState;
readWriteLock = new ReentrantReadWriteLock();
conditionListeners = new LinkedTransferQueue>();
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 = state;
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();
}
this.state = state;
// downgrading lock to read
if (locked) {
readWriteLock.readLock().lock();
readWriteLock.writeLock().unlock();
}
notifyConditionListeners(state);
if (locked) {
readWriteLock.readLock().unlock();
}
}
/**
* Gets Read/Write locker, which is used by this 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;
}
/**
* 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
* StateHolder's listener set.
* @param state State, listener is interested in
* @param notificationObject Object, which will be notified. This 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 notificationObject) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
ConditionListener conditionListener = null;
if (this.state.equals(state)) {
DefaultConditionListener.notifyListenerObject(notificationObject);
} else {
conditionListener = new OneTimeConditionListener();
conditionListener.set(new EqualCondition(state), notificationObject);
conditionListeners.add(conditionListener);
}
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 StateHolder's listener set.
* @param state State, listener is interested in
* @param notificationObject Object, which will be notified. This 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 notificationObject) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
ConditionListener conditionListener = null;
if (!this.state.equals(state)) {
DefaultConditionListener.notifyListenerObject(notificationObject);
} else {
conditionListener = new OneTimeConditionListener();
conditionListener.set(new NotEqualCondition(state), notificationObject);
conditionListeners.add(conditionListener);
}
if (isLockEnabledLocal) {
getStateLocker().writeLock().unlock();
}
return conditionListener;
}
/**
* Register listener, which will be notified, when state will match the condition.
* Once listener will be notified - it will be removed from this
* StateHolder's listener set.
* @param condition Condition, the listener is interested in
* @param notificationObject Object, which will be notified. This StateHolder
* implementation works with Runnable, Callable, CountDownLatch, Object
* listeners
* @return ConditionListener, 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 ConditionListener notifyWhenConditionMatchState(Condition condition, Object notificationObject) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
ConditionListener conditionListener = null;
if (condition.check(state)) {
DefaultConditionListener.notifyListenerObject(notificationObject);
} else {
conditionListener = new OneTimeConditionListener();
conditionListener.set(condition, notificationObject);
conditionListeners.add(conditionListener);
}
if (isLockEnabledLocal) {
getStateLocker().writeLock().unlock();
}
return conditionListener;
}
/**
* Add new ConditionListener to listen this StateHolder's
* state changes.
*
* @param conditionListener
*/
public void addConditionListener(ConditionListener conditionListener) {
boolean isLockEnabledLocal = isLockEnabled;
if (isLockEnabledLocal) {
getStateLocker().writeLock().lock();
}
if (conditionListener.checkConditionAndNotify(state)) {
if (conditionListener.isKeepAlive()) {
conditionListeners.add(conditionListener);
}
} else {
conditionListeners.add(conditionListener);
}
if (isLockEnabledLocal) {
getStateLocker().writeLock().unlock();
}
}
public void removeConditionListener(ConditionListener conditionListener) {
if (conditionListener == null) return;
conditionListeners.remove(conditionListener);
}
protected void notifyConditionListeners(E state) {
Iterator> it = conditionListeners.iterator();
while(it.hasNext()) {
ConditionListener listener = it.next();
try {
if (listener.checkConditionAndNotify(state) &&
!listener.isKeepAlive()) {
it.remove();
}
} catch(Exception e) {
_logger.log(Level.WARNING, "Error calling ConditionListener", e);
}
}
}
}