/*
* Created on May 24, 2007
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*
* Copyright @2007-2010 the original author or authors.
*/
package org.fest.swing.lock;
import static org.fest.util.Strings.concat;
import java.util.concurrent.locks.*;
import net.jcip.annotations.GuardedBy;
import net.jcip.annotations.ThreadSafe;
import org.fest.swing.exception.ScreenLockException;
/**
* Understands a lock that each GUI test should acquire before being executed, to guarantee sequential execution of
* GUI tests and to prevent GUI tests from blocking each other.
*
* @author Yvonne Wang
* @author Alex Ruiz
*/
@ThreadSafe
public final class ScreenLock {
private final Lock lock = new ReentrantLock();
private final Condition released = lock.newCondition();
@GuardedBy("lock")
private Object owner;
@GuardedBy("lock")
private boolean acquired;
/**
* Acquires this lock. If this lock was already acquired by another object, this method will block until the lock is
* released.
* @param newOwner the new owner of the lock.
*/
public void acquire(Object newOwner) {
lock.lock();
try {
if (alreadyAcquiredBy(newOwner)) return;
while (acquired) released.await();
owner = newOwner;
acquired = true;
} catch (InterruptedException ignored) {
Thread.currentThread().interrupt();
} finally {
lock.unlock();
}
}
/**
* Releases this lock.
* @param currentOwner the current owner of the lock.
* @throws ScreenLockException if the lock has not been previously acquired.
* @throws ScreenLockException if the given owner is not the same as the current owner of the lock.
*/
public void release(Object currentOwner) {
lock.lock();
try {
if (!acquired) throw new ScreenLockException("No lock to release");
if (owner != currentOwner) throw new ScreenLockException(concat(currentOwner, " is not the lock owner"));
acquired = false;
owner = null;
released.signal();
} finally {
lock.unlock();
}
}
/**
* Indicates whether this lock was acquired by the given object.
* @param possibleOwner the given object, which could be owning the lock.
* @return <code>true</code> if the given object is owning the lock; <code>false</code> otherwise.
*/
public boolean acquiredBy(Object possibleOwner) {
lock.lock();
try {
return alreadyAcquiredBy(possibleOwner);
} finally {
lock.unlock();
}
}
private boolean alreadyAcquiredBy(Object possibleOwner) {
return acquired && owner == possibleOwner;
}
/**
* Indicates whether this lock is already acquired.
* @return <code>true</code> if the lock is already acquired; <code>false</code> otherwise.
* @see #acquiredBy(Object)
* @since 1.2
*/
public boolean acquired() {
lock.lock();
try {
return acquired;
} finally {
lock.unlock();
}
}
/**
* Returns the singleton instance of this class.
* @return the singleton instance of this class.
*/
public static ScreenLock instance() { return ScreenLockHolder.instance; }
private static class ScreenLockHolder {
static ScreenLock instance = new ScreenLock();
}
ScreenLock() {}
}