动态代理实现dataSource ConnectionPool
编写连接池需实现java.sql.DataSource接口,
DataSource接口中定义了两个重载的getConnection方法：
Connection getConnection()
Connection getConnection(String username, String password)


没有close或release方法那么怎么 释放到池中呢？
所以通过动态代理实现
代码如下

public class JdbcPool implements DataSource {private static String driver;private static String url;private static  String username;private static String password;static{try {Properties prop = new Properties();InputStream in = JdbcUtil.class.getClassLoader().getResourceAsStream("db.properties");prop.load(in);driver = prop.getProperty("driver");url = prop.getProperty("url");username = prop.getProperty("username");password = prop.getProperty("password");Class.forName(driver);} catch (Exception e) {throw new ExceptionInInitializerError(e);}}private static LinkedList<Connection> pool = new LinkedList<Connection>();private static int poolsize = 10;//问题：每次newJdbcPoll都会建立10个链接，可使用单态设计模式解决此类问题public JdbcPool(){for(int i=0;i<poolsize;i++){try {Connection conn = DriverManager.getConnection(url,username,password);pool.add(conn);System.out.println(conn + "被加到池里面了！！！");} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}/* * 这里使用动态代理技术返回一个假的Connection，当dao调用假connection的任何方法时，该方法体内会调用InvocationHandler.invoke方法 * 在invoke方法体内，发现dao调用的是close方法，则把链接还到池里，否则，调用真connection的对应方法。 * (non-Javadoc) * @see javax.sql.DataSource#getConnection() */public Connection getConnection() throws SQLException { //spring aopif(pool.size()>0){final Connection conn = pool.removeFirst();System.out.println(conn + "从池里面取出去了！！！");return (Connection) Proxy.newProxyInstance(JdbcPool.class.getClassLoader(),conn.getClass().getInterfaces(), new InvocationHandler(){//proxy为代理对象 method为要调用的方法 args为方法的参数public Object invoke(Object proxy, Method method, Object[] args)throws Throwable {if(method.getName().equals("close")){pool.addFirst(conn);System.out.println(conn + "被还到池里面了！！");return null;}else{return method.invoke(conn, args);}}});}throw new RuntimeException("对不起，池里没有资源了！！！");}public Connection getConnection(String arg0, String arg1)throws SQLException {// TODO Auto-generated method stubreturn null;}public PrintWriter getLogWriter() throws SQLException {// TODO Auto-generated method stubreturn null;}public int getLoginTimeout() throws SQLException {// TODO Auto-generated method stubreturn 0;}public void setLogWriter(PrintWriter arg0) throws SQLException {// TODO Auto-generated method stub}public void setLoginTimeout(int arg0) throws SQLException {// TODO Auto-generated method stub}//public Jdbcpool}