创建数据库池实战

数据库池

package com.pool.utils;

/**
 * 数据库连接属性
 */
public class DBConstant {
    public final static String DRIVER_CLASS ="com.mysql.jdbc.Driver";
    public final static String URL ="jdbc:mysql:///dev_act";
    public final static String USERNAME ="root";
    public final static String PASSWORD = "123456";
    public final static String INIT_SIZE = "4";

}



package com.pool.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
 * 数据库连接工具类
 * 获取数据库连接对象
 */
public class DBConnUtil {

   static {
       try {
           Class.forName(DBConstant.DRIVER_CLASS);
       } catch (ClassNotFoundException e) {
           e.printStackTrace();
       }
   }


   public static Connection getConnection(){
       Connection connection =null;
       //1、通过DriverManager创建连接对象
       try {
           connection = DriverManager.getConnection(DBConstant.URL,DBConstant.USERNAME,DBConstant.PASSWORD);
       } catch (SQLException e) {
           e.printStackTrace();
       }
       return connection;
   }

}



package com.pool.utils;

import java.sql.*;
import java.util.LinkedList;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;

/**
 * 对原始Connection对象进行包装
 * 对close方法进行改写，调用它不是关闭连接而是归还连接到数据库池
 */
public class MyConnectionWarpper implements Connection {

    private Connection conn;
    private LinkedList<Connection> pool;
    MyConnectionWarpper(Connection conn, LinkedList<Connection> pool){
        this.conn = conn;
        this.pool = pool;
    }
    
    @Override
    public void close() throws SQLException {
        System.out.println("归还前："+pool.size());
        System.out.println(conn);
        pool.addLast(conn);
        System.out.println("归还后："+pool.size());
    }

    @Override
    public void commit() throws SQLException {
        conn.commit();
    }

    //省略Connection接口其它方法,其余方法调用原始Connection接口方法就行了.........
}




package com.pool.utils;

import java.sql.Connection;
import java.util.LinkedList;

/**
 * 什么时候释放连接池资源？
 * 通过监听器容器关闭时候清空MyDataSourcePool.pool =null;
 */
public class MyDataSourcePool {
    //多个连接对象用什么容器存储呢？
    private static LinkedList<java.sql.Connection> pool = new LinkedList<>();
    private static Integer initSize;
    //第一次类加载到JVM上的时候
    static{
        initSize = Integer.valueOf(DBConstant.INIT_SIZE);;
        for(int i=0;i<initSize;i++){
            pool.addLast(DBConnUtil.getConnection());
        }
    }

    /**
     * 返回封装/装饰后的Connection对象
     * 对原始Connection对象的close方法重新
     * @return
     */
    public Connection getConnection(){
        if(pool.isEmpty()){
            for(int i=0;i<initSize;i++){
                pool.addLast(DBConnUtil.getConnection());
            }
        }
        Connection conn = pool.removeFirst();
        MyConnectionWarpper connWarpper = new MyConnectionWarpper(conn,pool);
        return connWarpper;
    }

    /**
     * 归还连接方法
     */
    public static void releaseConnection(Connection conn){
        System.out.println("归还前："+pool.size());
        System.out.println(conn);
        pool.addLast(conn);
        System.out.println("归还后："+pool.size());
    }

}



package com.pool.utils;

import org.junit.Test;

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

/**
 * 数据库池测试类
 */
public class TestConn {

    @Test
    public void testConn(){
        System.out.println(DBConnUtil.getConnection());
    }

    public static void main(String[] args) {
        System.out.println(DBConnUtil.getConnection());
        //创建连接池
        MyDataSourcePool pool = new MyDataSourcePool();
        Connection conn = pool.getConnection();
        //pool.releaseConnection(conn);
        try {
            conn.close(); //不再是关闭连接对象，而是归还连接对象给数据库连接池
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}