数据源的编写（开发中不写）、使用动态代理覆写Connection的clos

import java.io.PrintWriter;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.SQLException;import java.util.LinkedList;import javax.sql.DataS

import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.LinkedList;

import javax.sql.DataSource;

import com.itheima.util.JdbcUtil;
//标准的数据库连接池。按照字面意思，一般叫做数据源（都是带池的，为了提高效率）
public class MyDataSource implements DataSource {
	
	private static LinkedList<Connection> pool = new LinkedList<Connection>();
	static{
		try {
			//池进行初始化：10个连接
			for(int i=0;i<10;i++){
				pool.add(JdbcUtil.getConnection());
			}
		} catch (Exception e) {
			throw new ExceptionInInitializerError("数据库连接池初始化失败");
		}
	}
	//返回它的包装类,会拦截connection中的所有方法
	@Override
	public synchronized Connection getConnection() throws SQLException {
		if(pool.size()>0){
			final Connection conn = pool.removeFirst();//原来的数据的connection实现。被包装类
			Connection proxyconn = (Connection)Proxy.newProxyInstance(conn.getClass().getClassLoader(),
					conn.getClass().getInterfaces(), 
					new InvocationHandler() {
						public Object invoke(Object proxy, Method method, Object[] args)
								throws Throwable {
							System.out.println(method.getName());
							if("close".equals(method.getName())){
								return pool.add(conn);
							}else{
								return method.invoke(conn, args);
							}
						}
					});
			return proxyconn;
		}else
			throw new RuntimeException("服务器忙");
	}
	
	
	@Override
	public PrintWriter getLogWriter() throws SQLException {
		return null;
	}

	@Override
	public void setLogWriter(PrintWriter out) throws SQLException {

	}

	@Override
	public void setLoginTimeout(int seconds) throws SQLException {

	}

	@Override
	public int getLoginTimeout() throws SQLException {
		return 0;
	}

	@Override
	public <T> T unwrap(Class<T> iface) throws SQLException {
		return null;
	}

	@Override
	public boolean isWrapperFor(Class<?> iface) throws SQLException {
		return false;
	}

	

	@Override
	public Connection getConnection(String username, String password)
			throws SQLException {
		return null;
	}

}

package com.jxnu.util;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
//通用的工具类：与具体数据库没有关系
public class JdbcUtil {
	
	private static String driverClass;
	private static String url;
	private static String username;
	private static String password;
	
	
	static{
		try {
			//加载配置文件
			InputStream in = JdbcUtil.class.getClassLoader().getResourceAsStream("dbcfg.properties");
			Properties props = new Properties();
			props.load(in);
			
			driverClass = props.getProperty("driverClass");
			url = props.getProperty("url");
			username = props.getProperty("username");
			password = props.getProperty("password");
			
			Class.forName(driverClass);
			
			
		} catch (Exception e) {
			throw new ExceptionInInitializerError(e);
		}
	}
	
	//获取数据库的连接
	public static Connection getConnection() throws Exception{
		Connection conn = DriverManager.getConnection(url, username, password);
		return conn;
	}
	//释放占用的资源
	public static void release(ResultSet rs,Statement stmt,Connection conn){
		if(rs!=null){
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if(stmt!=null){
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if(conn!=null){
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
}

测试：

package com.jxnu.pool04;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

public class Dao1Impl {
	MyDataSource ds = new MyDataSource();
	@Test
	public void add(){
		Connection conn  = null;
		Statement stmt = null;
		try{
			conn = ds.getConnection();
			stmt = conn.createStatement();
			//com.mysql.jdbc.Connection     :MySQL
			//com.oracle.jdbc.Connection    :Oracle
			//...
			System.out.println(conn.getClass().getName());
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			if(conn!=null){
				try {
					conn.close();//把连接给关了。不应该关，放回池中，怎么放回池中呢？连接池重点所在
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
	}
}