package com.direct.util;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

public class JDBCutil {

	/*

	 * 目前使用的JDBC连接数据库，存在问题：

	 * 每次连接和释放需要比较多的资源

	 * 资源浪费比较严重，系统的性能下滑

	 *

	 * 连接池的原理：

	 * 提前设定好，数据库的连接对象，当用户连接数据库时，直接从

	 * “池子”中取出一个连接即可。

	 * 当用户使用完毕后，“关闭连接”不是物理关闭，而是把连接放回连接池中

	 */

	private static final String DRIVER="com.mysql.jdbc.Driver";

	private static final String URL="jdbc:mysql://localhost:3306/countryside_buy?userUnicode=true&characterEncoding=utf-8";

	private static final String USER="root";

	private static final String PWD="123456";

	static{

		try {

			Class.forName(DRIVER);

		} catch (ClassNotFoundException e) {

			e.printStackTrace();

		}

	}

	//获得链接

	public Connection createConn(){

		Connection conn = null;

		try {

			conn = DriverManager.getConnection(URL, USER, PWD);

		} catch (SQLException e) {

			e.printStackTrace();

		}

		return conn;

	}

	//关闭连接

	public void closeJ(Connection conn,PreparedStatement ps,ResultSet rs) throws SQLException{

		if(rs!=null)  rs.close();

		if(ps!=null)  ps.close();

		if(conn!=null)  conn.close();

	}

}

username=root

password=123456

driverClassName=com.mysql.jdbc.Driver

maxActive=2000

maxIdle=520

maxWait=5000

url=jdbc\:mysql\://localhost\:3306/countryside_buy

package com.direct.util;

import java.sql.Connection;

import java.sql.SQLException;

import java.util.ResourceBundle;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;

/*

 * DBCP使用步骤：

 * 1，下载需要的jar包，放入web项目的lib下面

 * 2，在src下面建立配置文件   .properties

 * 3,   建立连接数据库工具，获取配置信息，

 * 4，commons-dbcp.jar

 *        commons-pool-1.5.3.jar

 *        musql-connector-java-5.1.7.jar

 */

public class DBCPutil {

	//数据源

	private static DataSource  ds= null;

	//基本数据源

	static BasicDataSource bds =  new BasicDataSource();

	public static Connection getconn() throws SQLException{

		if (ds==null) {

			ResourceBundle rs = ResourceBundle.getBundle("dbcp");

			String username = rs.getString("username");

			String password = rs.getString("password");

			String driverClassName = rs.getString("driverClassName");

			String maxActive = rs.getString("maxActive");

			String maxIdle = rs.getString("maxIdle");

			String maxWait = rs.getString("maxWait");

			String url = rs.getString("url");

			bds.setMaxActive(Integer.parseInt(maxActive));

			bds.setMaxIdle(Integer.parseInt(maxIdle));

			bds.setMaxWait(Integer.parseInt(maxWait));

			bds.setUrl(url);

			bds.setUsername(username);

			bds.setPassword(password);

			bds.setDriverClassName(driverClassName);

			ds = bds;

				return ds.getConnection();

		}

		return ds.getConnection();

	}

	//测试

	public static void main(String[] args) {

		try {

			System.out.println(getconn());

		} catch (SQLException e) {

			e.printStackTrace();

		}

	}

}

	<Resource

	  name="jndiDemo"

	  auth="Container"

	  type="javax.sql.DataSource"

      driverClassName="com.mysql.jdbc.Driver"

      url="jdbc:mysql://localhost:3306/countryside_buy"

	  username="root"

	  password="123456"

	  maxActive="100"

	  maxIdle="30"

	  maxWait="3000"

   />

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

	xmlns="http://java.sun.com/xml/ns/javaee"

	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

	<!-- 配置JNDI -->

	<resource-ref>

		<res-ref-name>jndiDemo</res-ref-name>

		<res-type>javax.sql.DataSource</res-type>

		<res-auth>Container</res-auth>

	</resource-ref>

<servlet>

    <description>This is the description of my J2EE component</description>

    <display-name>This is the display name of my J2EE component</display-name>

    <servlet-name>JndiServlet</servlet-name>

    <servlet-class>com.direct.servlet.JndiServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>JndiServlet</servlet-name>

    <url-pattern>/JndiServlet</url-pattern>

  </servlet-mapping>

  <welcome-file-list>

    <welcome-file>register.jsp</welcome-file>

  </welcome-file-list>

</web-app>

package com.direct.util;

import java.sql.Connection;

import java.sql.SQLException;

import javax.naming.Context;

import javax.naming.InitialContext;

import javax.naming.NamingException;

import javax.sql.DataSource;

public class JNDIutil {

	/*

	 * JNDI是tomcat提供的一种标准的连接池

	 * 1，将驱动放入项目中tomcat的lib目录下

	 * 2，修改配置文件（tomcat中找到config文件夹下的context.xml）

	 * 3，在web.xml下配置

	 */

	public static Connection conn(){

		Connection connection = null;

		try {

			//获得对数据源的引用

			Context context = new InitialContext();

			DataSource ds = (DataSource)context.lookup("java:comp/env/jndiDemo");

			//获得数据库连接对象

			connection = ds.getConnection();

		} catch (NamingException e) {

			e.printStackTrace();

		} catch (SQLException e) {

			e.printStackTrace();

		}

		return connection;

	}

}

package com.direct.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.direct.util.JNDIutil;

public class JndiServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		doPost(request, response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html");

		System.out.println(new JNDIutil().conn());

		//jdbc:mysql://localhost:3306/countryside_buy, UserName=root@localhost, MySQL-AB JDBC Driver

	}

}