org.wildfly.security.auth.realm.IdentitySharedExclusiveLock Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
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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;
}
}
}