org.mycore.util.concurrent.MCRReadWriteGuard Maven / Gradle / Ivy
/*
* This file is part of *** M y C o R e ***
* See http://www.mycore.de/ for details.
*
* MyCoRe is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* MyCoRe is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with MyCoRe. If not, see .
*/
package org.mycore.util.concurrent;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.Supplier;
/**
* A MCRReadWriteGuard acts like a {@link ReadWriteLock} but automatically wraps read and write operations accordingly.
* @author Thomas Scheffler (yagee)
*/
public class MCRReadWriteGuard {
private Lock readLock;
private Lock writeLock;
public MCRReadWriteGuard() {
this(new ReentrantReadWriteLock());
}
public MCRReadWriteGuard(ReadWriteLock readWriteLock) {
readLock = readWriteLock.readLock();
writeLock = readWriteLock.writeLock();
}
/**
* Executes the read operation while the read lock is locked.
* This is a sharable lock. Many reader
can be executed simultaneously
* when no write operation is running.
* @param reader a read operation that should be guarded.
* @return result of {@link Supplier#get()}
*/
public T read(Supplier reader) {
readLock.lock();
try {
return reader.get();
} finally {
readLock.unlock();
}
}
/**
* Executes the write operation while the write lock is locked.
* This is an exclusive lock. So no other read or write operation
* can be executed while operation
is running.
* @param operation
*/
public void write(Runnable operation) {
writeLock.lock();
try {
operation.run();
} finally {
writeLock.unlock();
}
}
public T lazyLoad(Supplier check, Runnable operation, Supplier reader) {
readLock.lock();
boolean holdsReadLock = true;
try {
if (check.get()) {
holdsReadLock = false;
readLock.unlock();
write(operation);
}
} finally {
if (holdsReadLock) {
readLock.unlock();
}
}
return reader.get();
}
}