int executeSQL(String sql) throws SQLException
{
	Connection conn = getConnection();	//通过某种方式获取数据库连接
	PreparedStatement ps = null;
	int res = 0;
	try{
		ps = conn.prepareStatement(sql);
		res = ps.executeUpdate();
}finally{
try{
ps.close();
}catch(Exception e){}
try{
	conn.close();//
}catch(Exception e){}
}
return res;
}

public interface InvocationHandler

InvocationHandler is the interface implemented by the invocation handler of a proxy instance. 

Each proxy instance has an associated invocation handler. 
When a method is invoked on a proxy instance, 
the method invocation is encoded and dispatched to the invoke method of its invocation handler.

public class ConnectionParam implements Serializable
{
	private String driver;				//数据库驱动程序
	private String url;					//数据连接的URL
	private String user;					//数据库用户名
	private String password;				//数据库密码
	private int minConnection = 0;		//初始化连接数
	private int maxConnection = 50;		//最大连接数
	private long timeoutValue = 600000;//连接的最大空闲时间
	private long waitTime = 30000;		//取连接的时候如果没有可用连接最大的等待时间

/**
 * 连接池类厂，该类常用来保存多个数据源名称合数据库连接池对应的哈希
 * @author liusoft
 */
public class ConnectionFactory
{
	//该哈希表用来保存数据源名和连接池对象的关系表
	static Hashtable connectionPools = null;
	static{
		connectionPools = new Hashtable(2,0.75F);
	} 
	/**
	 * 从连接池工厂中获取指定名称对应的连接池对象
	 * @param dataSource	连接池对象对应的名称
	 * @return DataSource	返回名称对应的连接池对象
	 * @throws NameNotFoundException	无法找到指定的连接池
	 */
	public static DataSource lookup(String dataSource) 
		throws NameNotFoundException
	{
		Object ds = null;
		ds = connectionPools.get(dataSource);
		if(ds == null || !(ds instanceof DataSource))
			throw new NameNotFoundException(dataSource);
		return (DataSource)ds;
	}

	/**
	 * 将指定的名字和数据库连接配置绑定在一起并初始化数据库连接池
	 * @param name		对应连接池的名称
	 * @param param	连接池的配置参数，具体请见类ConnectionParam
	 * @return DataSource	如果绑定成功后返回连接池对象
	 * @throws NameAlreadyBoundException	一定名字name已经绑定则抛出该异常
	 * @throws ClassNotFoundException		无法找到连接池的配置中的驱动程序类
	 * @throws IllegalAccessException		连接池配置中的驱动程序类有误
	 * @throws InstantiationException		无法实例化驱动程序类
	 * @throws SQLException				无法正常连接指定的数据库
	 */
	public static DataSource bind(String name, ConnectionParam param)
		throws NameAlreadyBoundException,ClassNotFoundException,
				IllegalAccessException,InstantiationException,SQLException
	{
		DataSourceImpl source = null;
		try{
			lookup(name);
			throw new NameAlreadyBoundException(name);
		}catch(NameNotFoundException e){
			source = new DataSourceImpl(param);
			source.initConnection();
			connectionPools.put(name, source);
		}
		return source;
	}
	/**
	 * 重新绑定数据库连接池
	 * @param name		对应连接池的名称
	 * @param param	连接池的配置参数，具体请见类ConnectionParam
	 * @return DataSource	如果绑定成功后返回连接池对象
	 * @throws NameAlreadyBoundException	一定名字name已经绑定则抛出该异常
	 * @throws ClassNotFoundException		无法找到连接池的配置中的驱动程序类
	 * @throws IllegalAccessException		连接池配置中的驱动程序类有误
	 * @throws InstantiationException		无法实例化驱动程序类
	 * @throws SQLException				无法正常连接指定的数据库
	 */
	public static DataSource rebind(String name, ConnectionParam param)
		throws NameAlreadyBoundException,ClassNotFoundException,
				IllegalAccessException,InstantiationException,SQLException
	{
		try{
			unbind(name);
		}catch(Exception e){}
		return bind(name, param);
	}
	/**
	 * 删除一个数据库连接池对象
	 * @param name
	 * @throws NameNotFoundException
	 */
	public static void unbind(String name) throws NameNotFoundException
	{
		DataSource dataSource = lookup(name);
		if(dataSource instanceof DataSourceImpl){
			DataSourceImpl dsi = (DataSourceImpl)dataSource;
			try{
				dsi.stop();
				dsi.close();
			}catch(Exception e){
			}finally{
				dsi = null;
			}
		}
		connectionPools.remove(name);
	}
	
}

	String name = "pool";
	String driver = " sun.jdbc.odbc.JdbcOdbcDriver ";
	String url = "jdbc:odbc:datasource";
	ConnectionParam param = new ConnectionParam(driver,url,null,null);
	param.setMinConnection(1);
	param.setMaxConnection(5);
	param.setTimeoutValue(20000);
	ConnectionFactory.bind(name, param);
	System.out.println("bind datasource ok.");
	//以上代码是用来登记一个连接池对象，该操作可以在程序初始化只做一次即可
	//以下开始就是使用者真正需要写的代码
	DataSource ds = ConnectionFactory.lookup(name);
	try{
		for(int i=0;i<10;i++){
			Connection conn = ds.getConnection();
			try{
				testSQL(conn, sql);
			}finally{
				try{
					conn.close();
				}catch(Exception e){}
			}
		}
	}catch(Exception e){
		e.printStackTrace();
	}finally{
		ConnectionFactory.unbind(name);
		System.out.println("unbind datasource ok.");
		System.exit(0);
	}

source = new DataSourceImpl(param);
source.initConnection();

/**
 * @see javax.sql.DataSource#getConnection(String,String)
 */
	public Connection getConnection(String user, String password) throws SQLException 
	{
		//首先从连接池中找出空闲的对象
		Connection conn = getFreeConnection(0);
		if(conn == null){
			//判断是否超过最大连接数,如果超过最大连接数
			//则等待一定时间查看是否有空闲连接,否则抛出异常告诉用户无可用连接
			if(getConnectionCount() >= connParam.getMaxConnection())
				conn = getFreeConnection(connParam.getWaitTime());
			else{//没有超过连接数，重新获取一个数据库的连接
				connParam.setUser(user);
				connParam.setPassword(password);
				Connection conn2 = DriverManager.getConnection(connParam.getUrl(), 
				user, password);
				//代理将要返回的连接对象
				_Connection _conn = new _Connection(conn2,true);
				synchronized(conns){
					conns.add(_conn);
				}
				conn = _conn.getConnection();
			}
		}
		return conn;
	}
	/**
	 * 从连接池中取一个空闲的连接
	 * @param nTimeout	如果该参数值为0则没有连接时只是返回一个null
	 * 否则的话等待nTimeout毫秒看是否还有空闲连接，如果没有抛出异常
	 * @return Connection
	 * @throws SQLException
	 */
	protected synchronized Connection getFreeConnection(long nTimeout) 
		throws SQLException
	{
		Connection conn = null;
		Iterator iter = conns.iterator();
		while(iter.hasNext()){
			_Connection _conn = (_Connection)iter.next();
			if(!_conn.isInUse()){
				conn = _conn.getConnection();
				_conn.setInUse(true);				
				break;
			}
		}
		if(conn == null && nTimeout > 0){
			//等待nTimeout毫秒以便看是否有空闲连接
			try{
				Thread.sleep(nTimeout);
			}catch(Exception e){}
			conn = getFreeConnection(0);
			if(conn == null)
				throw new SQLException("没有可用的数据库连接");
		}
		return conn;
	}

/**
 * 数据连接的自封装，屏蔽了close方法
 * @author Liudong
 */
class _Connection implements InvocationHandler
{
	private final static String CLOSE_METHOD_NAME = "close";
	private Connection conn = null;
	//数据库的忙状态
	private boolean inUse = false;
	//用户最后一次访问该连接方法的时间
	private long lastAccessTime = System.currentTimeMillis();
	
	_Connection(Connection conn, boolean inUse){
		this.conn = conn;
		this.inUse = inUse;
	}
	/**
	 * Returns the conn.
	 * @return Connection
	 */
	public Connection getConnection() {
		//返回数据库连接conn的接管类，以便截住close方法
		Connection conn2 = (Connection)Proxy.newProxyInstance(
			conn.getClass().getClassLoader(),
			conn.getClass().getInterfaces(),this);
		return conn2;
	}
	/**
	 * 该方法真正的关闭了数据库的连接
	 * @throws SQLException
	 */
	void close() throws SQLException{
		//由于类属性conn是没有被接管的连接，因此一旦调用close方法后就直接关闭连接
		conn.close();
	}
	/**
	 * Returns the inUse.
	 * @return boolean
	 */
	public boolean isInUse() {
		return inUse;
	}

	/**
	 * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object)
	 */
	public Object invoke(Object proxy, Method m, Object[] args) 
		throws Throwable 
	{
		Object obj = null;
		//判断是否调用了close的方法，如果调用close方法则把连接置为无用状态
		if(CLOSE_METHOD_NAME.equals(m.getName()))
			setInUse(false);		
		else
			obj = m.invoke(conn, args);	
		//设置最后一次访问时间，以便及时清除超时的连接
		lastAccessTime = System.currentTimeMillis();
		return obj;
	}
		
	/**
	 * Returns the lastAccessTime.
	 * @return long
	 */
	public long getLastAccessTime() {
		return lastAccessTime;
	}

	/**
	 * Sets the inUse.
	 * @param inUse The inUse to set
	 */
	public void setInUse(boolean inUse) {
		this.inUse = inUse;
	}
}

	/**
	 * 关闭该连接池中的所有数据库连接
	 * @return int 返回被关闭连接的个数
	 * @throws SQLException
	 */
	public int close() throws SQLException
	{
		int cc = 0;
		SQLException excp = null;
		Iterator iter = conns.iterator();
		while(iter.hasNext()){
			try{
				((_Connection)iter.next()).close();
				cc ++;
			}catch(Exception e){
				if(e instanceof SQLException)
					excp = (SQLException)e;
			}
		}
		if(excp != null)
			throw excp;
		return cc;
	}