LocalLockManager.java :  » Database-JDBC-Connection-Pool » HA-JDBC » net » sf » hajdbc » local » Java Open Source

/*
 * HA-JDBC: High-Availability JDBC
 * Copyright (c) 2004-2007 Paul Ferraro
 * 
 * This library is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by the 
 * Free Software Foundation; either version 2.1 of the License, or (at your 
 * option) any later version.
 * 
 * This library 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 Lesser General Public License 
 * for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, 
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 * 
 * Contact: ferraro@users.sourceforge.net
 */
package net.sf.hajdbc.local;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;

import net.sf.hajdbc.LockManager;
import net.sf.hajdbc.util.concurrent.SemaphoreReadWriteLock;

/**
 * @author Paul Ferraro
 */
public class LocalLockManager implements LockManager
{
  private Map<String, ReadWriteLock> lockMap = new HashMap<String, ReadWriteLock>();

  /**
   * @see net.sf.hajdbc.LockManager#readLock(java.lang.String)
   */
  @Override
  public Lock readLock(String object)
  {
    Lock lock = this.getReadWriteLock(null).readLock();
    
    return (object == null) ? lock : new GlobalLock(lock, this.getReadWriteLock(object).readLock());
  }
  
  /**
   * @see net.sf.hajdbc.LockManager#writeLock(java.lang.String)
   */
  @Override
  public Lock writeLock(String object)
  {
    ReadWriteLock readWriteLock = this.getReadWriteLock(null);
    
    return (object == null) ? readWriteLock.writeLock() : new GlobalLock(readWriteLock.readLock(), this.getReadWriteLock(object).writeLock());
  }
  
  private synchronized ReadWriteLock getReadWriteLock(String object)
  {
    ReadWriteLock lock = this.lockMap.get(object);
    
    if (lock == null)
    {
      lock = new SemaphoreReadWriteLock();
      
      this.lockMap.put(object, lock);
    }
    
    return lock;
  }
  
  private static class GlobalLock implements Lock
  {
    private Lock globalLock;
    private Lock lock;
    
    GlobalLock(Lock globalLock, Lock lock)
    {
      this.globalLock = globalLock;
      this.lock = lock;
    }
    
    @Override
    public void lock()
    {
      this.globalLock.lock();
      this.lock.lock();
    }

    @Override
    public void lockInterruptibly() throws InterruptedException
    {
      this.globalLock.lockInterruptibly();
      
      try
      {
        this.lock.lockInterruptibly();
      }
      catch (InterruptedException e)
      {
        this.globalLock.unlock();
        throw e;
      }
    }

    @Override
    public boolean tryLock()
    {
      if (this.globalLock.tryLock())
      {
        if (this.lock.tryLock())
        {
          return true;
        }

        this.globalLock.unlock();
      }

      return false;
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException
    {
      if (this.globalLock.tryLock(time, unit))
      {
        if (this.lock.tryLock(time, unit))
        {
          return true;
        }

        this.globalLock.unlock();
      }

      return false;
    }

    @Override
    public void unlock()
    {
      this.lock.unlock();
      this.globalLock.unlock();
    }

    @Override
    public Condition newCondition()
    {
      throw new UnsupportedOperationException();
    }
  }

  /**
   * @see net.sf.hajdbc.LockManager#start()
   */
  @Override
  public void start() throws Exception
  {
    // Do nothing
  }

  /**
   * @see net.sf.hajdbc.LockManager#stop()
   */
  @Override
  public void stop()
  {
    // Do nothing
  }
}