org.wildfly.security.auth.realm.IdentitySharedExclusiveLock Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source.
* Copyright 2016 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* 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.
*/
package org.wildfly.security.auth.realm;
/**
* A simple shared/exclusive lock for a realm identity.
*
* @author Farah Juma
*/
public class IdentitySharedExclusiveLock {
private int sharedHoldCount;
private boolean isExclusiveLocked;
private int exclusiveRequests;
/**
* Acquire the exclusive lock. An invocation of this method will block until the lock can be acquired.
*
* @return a lock object representing the newly acquired lock
*/
public synchronized IdentityLock lockExclusive() {
boolean interrupted = false;
try {
exclusiveRequests++;
while ((sharedHoldCount > 0) || isExclusiveLocked) {
try {
wait();
} catch (InterruptedException e) {
interrupted = true;
}
}
isExclusiveLocked = true;
exclusiveRequests--;
return new IdentityLock(true);
} finally {
if (interrupted) {
Thread.currentThread().interrupt();
}
}
}
/**
* Acquire a shared lock. An invocation of this method will block until the lock can be acquired.
*
* @return a lock object representing the newly acquired lock
*/
public synchronized IdentityLock lockShared() {
boolean interrupted = false;
try {
while (isExclusiveLocked || (exclusiveRequests > 0)) {
try {
wait();
} catch (InterruptedException e) {
interrupted = true;
}
}
sharedHoldCount++;
return new IdentityLock(false);
} finally {
if (interrupted) {
Thread.currentThread().interrupt();
}
}
}
private synchronized void release(IdentityLock identityLock) {
if (identityLock.isExclusive()) {
isExclusiveLocked = false;
notifyAll();
} else {
if (--sharedHoldCount == 0) {
notifyAll();
}
}
}
/**
* Class that represents a lock on a realm identity. A lock object is created each time a lock is
* acquired on a realm identity via {@link IdentitySharedExclusiveLock#lockExclusive()} or
* {@link IdentitySharedExclusiveLock#lockShared()}.
*/
public class IdentityLock implements AutoCloseable {
private final boolean exclusive;
private volatile boolean valid = true;
/**
* Construct a new instance.
*
* @param exclusive {@code true} if this lock is exclusive, {@code false} if this lock is shared
*/
public IdentityLock(final boolean exclusive) {
this.exclusive = exclusive;
}
/**
* Release this lock. Invoking this method has no effect if this lock is invalid.
*/
public synchronized void release() {
if (valid) {
IdentitySharedExclusiveLock.this.release(this);
valid = false;
}
}
@Override
public void close() {
release();
}
/**
* Determine whether this lock is exclusive or shared.
*
* @return {@code true} if this lock is exclusive, {@code false} if this lock is shared
*/
public boolean isExclusive() {
return exclusive;
}
/**
* Determine whether this lock is valid. A lock starts out valid and becomes invalid when it
* is released via {@link #release()} or {@link #close()}.
*
* @return {@code true} if this lock is valid, {@code false} otherwise
*/
public boolean isValid() {
return valid;
}
}
}