注意：使用装饰者模式增强Connection的close方法

1. 测试部分

package com.it.jdbc.TestDataSoure;

import java.sql.Connection;
import java.sql.PreparedStatement;
import javax.management.RuntimeErrorException;
import org.junit.Test;
import com.it.jdbc.DataSoure.MyDataSoure;
import com.it.jdbc.utils.JDBCUtils_V3;

public class TestMyDataSoure {
    /**
     * 添加用户
     * 使用改造Connection
     */
    @Test
    public void testAdduser1() {
    Connection conn = null;
    PreparedStatement pstmt = null;
    // 自定义连接池对象
    MyDataSoure datasoure = new MyDataSoure();
    try {
        // 从连接池获得链接
        conn = datasoure.getConnection();
        String sql = "insert into use1 value(null,?,?)";
        pstmt =conn.prepareStatement(sql);
        pstmt.setString(1, "何一");
        pstmt.setString(2, "李二");
        int rows = pstmt.executeUpdate();
        if (rows > 0) {
            System.out.println("添加成功");
        } else {
            System.out.println("添加失败");
        }
    } catch (Exception e) {
        throw new RuntimeException(e);
    } finally {
        JDBCUtils_V3.release(conn, pstmt, null);
    }
}
}

2.MyConnection

package com.it.jdbc.DataSoure;

import java.sql.Array;
import java.sql.Blob;
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.NClob;
import java.sql.PreparedStatement;
import java.sql.SQLClientInfoException;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.LinkedList;
import java.util.Map;
import java.util.Properties;
//1，实现同一个接口
public class MyConnection implements Connection{
    //3,定义一个变量
    private Connection conn;
    private LinkedList<Connection> pool;
    //写构造方法(参数使用了面向对象-多态)
    public MyConnection (Connection conn,LinkedList<Connection> pool){
        this.conn =conn;
        this.pool=pool;
    }
    //增强的方法
    @Override
    public void close() throws SQLException {
        // TODO Auto-generated method stub
        pool.add(conn);
    }
    @Override
    //此方法必须覆盖，否则空指针异常 
        public PreparedStatement prepareStatement(String sql) throws SQLException {
        // TODO Auto-generated method stub
        return conn.prepareStatement(sql);
    }
}

3.MyDataSoure

package com.it.jdbc.DataSoure;

import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.LinkedList;
import javax.sql.DataSource;
import com.it.jdbc.utils.JDBCUtils_V3;

public class MyDataSoure implements DataSource {
    // 1,创建一个容器，存储Connection对象
    private static LinkedList<Connection> pool = new LinkedList<Connection>();
    // 2,创建5个链接放到容器中
    static {
        for (int i = 0; i < 5; i++) {
            Connection conn = JDBCUtils_V3.getConnection();
            MyConnection myconn= new MyConnection(conn, pool);
            pool.add(myconn);
        }
    }

    @Override
    public Connection getConnection() throws SQLException {
        Connection conn = null;
        // 3，使用前判断
        if (pool.size() == 0) {
            // 4,添加链接
            for (int i = 0; i < 5; i++) {
                conn = JDBCUtils_V3.getConnection();
            //连接池中的自定义myconn
                MyConnection myconn= new MyConnection(conn, pool);
                pool.add(myconn);
            }
        }
        // 5,从连接池获取一个链接对象Connection
        conn = pool.remove(0);
        return conn;
    }

    public void backConnection(Connection conn) {
        // 归还连接池
        pool.add(conn);
    }


}