dblogger.java

这是一款应用程序与数据库联接

/* ===========================================================
 * JDBMonitor : a flexiable JDBC Monitor for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2006-2006, by yang zhongke
 *
 * Project Info:  http://www.cownew.com
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
 * USA.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ---------------
 * DBLogger.java
 * ---------------
 * (C) Copyright 2006-2006, by yang zhongke
 *
 * Original Author:  yang zhongke;
 *
 * Changes
 * -------
 *
 */
package com.cownew.JDBMonitor.common;

import java.sql.SQLException;

/**
 * the Class receive the SQLInfos ,
 * the LogConsumer is in another Thread,it dispatch the these SQLInfos to the DBListeners
 * @author yang zhongke
 */
public class DBLogger
{
	private static final int SHUTDOWNSLEEPMSECOND = 1000;
	private static IChannel channel;
	private static IDBListener[] dbListeners;
	
	private static DBLogger instance;
	
	private DBLogger(DBListenerInfo[] dbListenerInfos) throws LoggerException, SQLException
	{
		// instante the DBListener class 
		dbListeners = new IDBListener[dbListenerInfos.length];		
		for(int i=0,n=dbListenerInfos.length;i<n;i++)
		{
			DBListenerInfo info = dbListenerInfos[i];
			IDBListener lis;
			try
			{
				lis = (IDBListener) info.getListenerClass().newInstance();
			} catch (InstantiationException e)
			{
				throw LoggerUtils.toLoggerException(e);
			} catch (IllegalAccessException e)
			{
				throw LoggerUtils.toLoggerException(e);
			}
			lis.init(info.getArguments());
			dbListeners[i] = lis;
		}
	}
	
	/**
	 * get the single instance of DBLogger
	 * @param dbListenerInfos
	 * @return
	 * @throws LoggerException
	 * @throws SQLException
	 */
	public static synchronized DBLogger getLogger(DBListenerInfo[] dbListenerInfos) 
	throws LoggerException, SQLException
	{
		if(instance==null)
		{
			instance = new DBLogger(dbListenerInfos);
		}
		return instance;
	}
	
	/**
	 * log the SQLInfo,put it to the channel
	 * @param info
	 * @throws LoggerException
	 */
	public synchronized void logSQL(SQLInfo info) throws LoggerException
	{
		try
		{
			channel.offer(info);
		} catch (InterruptedException e)
		{
			throw LoggerUtils.toLoggerException(e);
		}
	}
	
	/**
	 * the dispatcher of SQLInfos,it dispatchs SQLInfos to the listeners
	 * @author yang zhongke
	 */
	static class LogConsumer implements Runnable
	{
		public void run()
		{
			try
			{
				startConsumer();
			} catch (InterruptedException e)
			{
				throw CommonUtils.toRuntimeException(e);
			} catch (LoggerException e)
			{
				throw CommonUtils.toRuntimeException(e);
			}
		}
		
		private void startConsumer() throws LoggerException, InterruptedException
		{
			for (;;)
			{
				SQLInfo info = (SQLInfo) channel.take();
				for (int i = 0, n = dbListeners.length; i < n; i++)
				{
					dbListeners[i].logSql(info);
				}

			}
		}
		
	}
	
	static
	{
		channel = new BlockedChannel();
		
		//add hook to the JVM,when JVM will shutDown
		//the hook will be executed
		Runtime.getRuntime().addShutdownHook(new Thread(){
			public void run()
			{
				//once JVM will shutDown,this hook will pause the shutingdown
				//until all the SQLInfo be dispatched
				while (!channel.isEmpty())
				{
					try
					{
						Thread.sleep(SHUTDOWNSLEEPMSECOND);
					} catch (Exception e)
					{
						throw CommonUtils.toRuntimeException(e);
					}
				}
			}
		});		
		
		//start the SQLInfo consumer thread
		Thread consumerThread = new Thread(new LogConsumer());
		consumerThread.setDaemon(true);
		consumerThread.start();
	}

}