pooledconnectionmgr.java

本人课程设计时做的一个用struts框架实现的基于cmmi2的项目管理系统的原型。还有部分功能尚未实现

	*/
	private void close(PooledConnection pooledCon)
	{
		if (pooledCon != null)
		{
			//System.out.println( "关闭连接:"+pooledCon.getTimeTagID() );
			if (pooledCon.con != null)
			{
				try
				{		    
					// Close the connection
					pooledCon.con.close();
				}
				catch (Exception ex)
				{
					// Ignore any exceptions during close
				}
				
				// Clear the connection object reference
				pooledCon.con = null;
			}
		}
	}
	
	/**
	* <p>Creates the initial connection pool. A timer thread
	* is also created so that connection timeouts can be
	* handled.
	*
	* @return true if the pool was created
	*/
	private void createPool() throws Exception
	{
		// Sanity check our properties
		if (JDBCDriver == null)
		{
			//System.out.println( "JDBCDriver 未初始化" );
			throw new Exception("JDBCDriver property not found");
		}
		if (JDBCConnectionURL == null)
		{
			//System.out.println( "JDBCConnectionURL 未初始化" );
			throw new Exception("JDBCConnectionURL property not found");
		}
		if (connectionPoolSize < 0)
		{
			//System.out.println( "ConnectionPoolSize 未初始化" );
			throw new Exception("ConnectionPoolSize property not found");
		}
		if (connectionPoolSize == 0)
		{
			//System.out.println( "ConnectionPoolSize 非法" );
			throw new Exception("ConnectionPoolSize invalid");
		}
		if (connectionPoolMax < connectionPoolSize)
		{
			//System.out.println( "最大连接数非法，将被忽略" );
			connectionPoolMax = -1;
		}
		if (connectionTimeout < 0)
		{
			// Set the default to 30 minutes
			connectionTimeout = 30;
		}
		
		//System.out.println("JDBCDriver = " + JDBCDriver);
		//System.out.println("JDBCConnectionURL = " + JDBCConnectionURL);
		//System.out.println("ConnectionPoolSize = " + connectionPoolSize);
		//System.out.println("ConnectionPoolMax = " + connectionPoolMax);
		//System.out.println("ConnectionUseCount = " + connectionUseCount);
		//System.out.println("ConnectionTimeout = " + connectionTimeout +" seconds");
		
		// Attempt to create a new instance of the specified
		// JDBC driver. Well behaved drivers will register
		// themselves with the JDBC DriverManager when they
		// are instantiated
		//System.out.println("Registering " + JDBCDriver);
		java.sql.Driver d = (java.sql.Driver)
		Class.forName(JDBCDriver).newInstance();
		// Create the vector for the pool
		pool = new java.util.Vector();
		
		// Bring the pool to the minimum size
		fillPool(connectionPoolSize);
	}
		
	/**
	* <p>Adds a new connection to the pool
	*
	* @return Index of the new pool entry, or -1 if an
	* error has occurred
	*/
	private int addConnection() throws Exception
	{
		int index = -1;
		
		try
		{
			// Calculate the new size of the pool
			int size = pool.size() + 1;
			
			// Create a new entry
			fillPool(size);
			
			// Set the index pointer to the new connection if one
			// was created
			if (size == pool.size())
			{
				index = size - 1;
			}
		}
		catch (Exception ex)
		{
			throw new Exception(ex);
		}
		return index;
	}
	
	/**
	* <p>Brings the pool to the given size
	* @throws Exception
	*/
	private synchronized void fillPool(int size) throws Exception
	{
		//System.out.println( "填充连接池开始" );
		while (pool.size() < size)
		{
			PooledConnection pc = new PooledConnection();  
			pc.con = DriverManager.getConnection( JDBCConnectionURL,
			                                      userName,
			                                      passWord);
			// Do some sanity checking on the first connection in
			// the pool
			if (pool.size() == 0)
			{
			
				// Get the maximum number of simultaneous connections
				// as reported by the JDBC driver
				java.sql.DatabaseMetaData md = pc.con.getMetaData();
				maxConnections = md.getMaxConnections();
			}
			
			// Give a warning if the size of the pool will exceed
			// the maximum number of connections allowed by the
			// JDBC driver
			if ((maxConnections > 0) &&
			    (size > maxConnections))
			{
				//System.out.println("警告: 连接池已达到安全的上限 " + maxConnections);
			}
			
			// Clear the in use flag
			pc.inUse = false;
			
			// Set the last access time
			touch(pc);
			pool.addElement(pc);
			//System.out.println( "增加连接:"+pc.getTimeTagID() );
		}
		//System.out.println( "填充连接池结束   当前池的大小="+pool.size() );
	}
	
	/**
	* <p>Find the given connection in the pool
	*
	* @return Index into the pool, or -1 if not found
	*/
	private int find(java.sql.Connection con)
	{
		int index = -1;
		
		// Find the matching Connection in the pool
		if ((con != null) &&(pool != null))
		{
			for (int i = 0; i < pool.size(); i++)
			{
				PooledConnection pc = (PooledConnection)pool.elementAt(i);
				if (pc.con == con)
				{
					index = i;
					break;
				}
			}
		}
		return index;
	}
	
	/**
	* <p>Called by the timer each time a clock cycle expires.
	* This gives us the opportunity to timeout connections
	*/
	public synchronized void TimerEvent(Object object)
	{
		//System.out.println( "定时检查开始" );
		// No pool means no work
		if (pool == null)
		{
			//System.out.println("The pool is empty!!!");
			return;
		}
		
		// Get the current time in milliseconds
		long now = System.currentTimeMillis();
		
		// Check for any expired connections and remove them
		for (int i = pool.size() - 1; i >= 0; i--)
		{
			PooledConnection pc = (PooledConnection)pool.elementAt(i);
			
			// If the connection is not in use and it has not been
			// used recently, remove it
			if (!pc.inUse)
			{
				if ((connectionTimeout > 0) &&(pc.lastAccess +(connectionTimeout * 1000) < now))
				{
					//System.out.println( "连接超时，即将关闭:"+pc.getTimeTagID() );
					removeFromPool(i);
				}
			}
		}
		
		// Remove any connections that are no longer open
		for (int i = pool.size() - 1; i >= 0; i--)
		{
			PooledConnection pc = (PooledConnection)pool.elementAt(i);
			try
			{
				// If the connection is closed, remove it from the pool
				if (pc.con.isClosed())
				{
					//System.out.println("连接异常关闭:"+pc.getTimeTagID());
					removeFromPool(i);
				}
			}
			catch (Exception ex)
			{
			}
		}
		
		// Now ensure that the pool is still at it's minimum size
		try
		{
			if (pool != null)
			{
				if (pool.size() < connectionPoolSize)
				{
					fillPool(connectionPoolSize);
				}
			}
		}
		catch (Exception ex)
		{
			ex.printStackTrace();
		}
		//System.out.println( "定时检查结束" );
	}
	
	/**
	* <p>Sets the last access time for the given PooledConnection
	*/
	private void touch(PooledConnection pc)
	{
		if (pc != null)
		{
			pc.lastAccess = System.currentTimeMillis();
		}
	}
	
	/*
	* <p>System.out.println the given string
	*    At present the log infromation has been printed in the console.
	*
	private void System.out.println(String s)
	{
		//logFile.writeLog( s );
		System.out.println(s);
	}
	
	public static void main(String[] args)
	{
		try
		{
			PooledConnectionMgr pool = PooledConnectionMgr.getInstance();
			pool.setJDBCDriver( "org.gjt.mm.mysql.Driver" );
			pool.setJDBCConnectionURL( "jdbc:mysql://192.168.15.150:3306/CMMI2PM" );
			pool.setConnectionPoolSize( 5 );
			pool.setConnectionPoolMax( 10 );
			pool.setConnectionUseCount( 8 );
			pool.setConnectionTimeout( 30 );
			
			pool.initialize(30);
		
			Connection con= pool.getConnection();
			Statement s = con.createStatement();
			ResultSet rs = s.executeQuery("SELECT * FROM user ");
			System.out.println("ID\tusername\tfull_name\tpassword");
			while(rs.next())
			{
				System.out.println(rs.getString(1)+"\t"+rs.getString(2)+"\t\t"+rs.getString(3)+"\t"+rs.getString(4));
			}
			System.out.println("--------end--------");
			s.close();
			pool.printPool();
			pool.close( con );
			
			pool.destroy();
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}
	*/
	public java.sql.Connection getConnection() throws Exception
	{
		java.util.Date d = new java.util.Date();
		java.sql.Connection con = null;
		long enterTime = (long) d.getTime();
		while( con==null )
		{
			long curTime = (long) d.getTime();
			if( curTime-enterTime > waitTimeOut*1000 )
			{
				throw new Exception("系统忙,请稍后重试!");
			}
			con = getValidConnection();
			if( con == null)
			{
				synchronized( d )
				{
					try
					{
						wait(20);
					}
					catch( InterruptedException e ){}    	     
				}
			}		   
		}
		return con;
	}
	
}