<?xml version='1.0' encoding='utf-8'?>

<!--

  Licensed to the Apache Software Foundation (ASF) under one or more

  contributor license agreements.  See the NOTICE file distributed with

  this work for additional information regarding copyright ownership.

  The ASF licenses this file to You under the Apache License, Version 2.0

  (the "License"); you may not use this file except in compliance with

  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software

  distributed under the License is distributed on an "AS IS" BASIS,

  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  See the License for the specific language governing permissions and

  limitations under the License.

-->

<!-- The contents of this file will be loaded for each web application -->

<Context reloadable="true">

    <!-- Default set of monitored resources -->

    <WatchedResource>WEB-INF/web.xml</WatchedResource>

    <!-- Uncomment this to disable session persistence across Tomcat restarts -->

    <!--

    <Manager pathname="" />

    -->

    <!-- Uncomment this to enable Comet connection tacking (provides events

         on session expiration as well as webapp lifecycle) -->

    <!--

    <Valve className="org.apache.catalina.valves.CometConnectionManagerValve" />

    -->

    <Resource name="jdbc/DBWater" auth="Container"

    	Type="javax.sql.DataSource"

    	maxActive="100" maxIdle="30" maxWait="10000"

    	username="root" password="root"

    	driverClassName="com.mysql.jdbc.Driver"

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

    />

</Context>

//引入包

package com.cjg.test;

import java.sql.Connection;

import java.sql.ResultSet;

import javax.naming.InitialContext;

import javax.sql.DataSource;

import java.sql.Statement;

public class DBWater {

	//定义三个对象name 、number、sex

	String name;

	int number;

	boolean sex;

	public String getName() {

		return name;

	}

	public int getNumber() {

		return number;

	}

	public boolean isSex() {

		return sex;

	}

    //初始化一些对象

	public void init() {

        try {

            //创建InitialContext对象

        	InitialContext initc  = new InitialContext();

            if (initc == null)

                throw new Exception("No Context");

            /*

             * 在下面的字符串"java:comp/env/jdbc/DBWater"中，*"java:comp/env/"是不变的，

             * 而"jdbc/DBWater"配置文件数据源名称

             */

            DataSource ds = (DataSource)initc.lookup("java:comp/env/jdbc/DBWater");

            if (ds != null) {

                Connection conn = ds.getConnection();                    //得到连接对象

                if (conn != null) {

                	Statement stmt=conn.createStatement();      //创建陈述对象

                    //得到运行结果

                    ResultSet rst=stmt.executeQuery("select   *   from   student");

                    //遍历运行结果

                    while (rst.next()) {

                        number=rst.getInt(1);

                        name=rst.getString(2);

                    }

                    conn.close();                                         //关闭连接对象

                }

            }

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

}

<?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">

  <welcome-file-list>

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

  </welcome-file-list>

   <resource-ref>

   <!-- 描述信息 -->

    <description>Connection Pool</description>

    <!-- 数据源名字 -->

    <res-ref-name>jdbc/DBWater</res-ref-name>

    <!-- 数据源的类型 -->

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

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

    <res-sharing-scope>Shareable</res-sharing-scope>

 </resource-ref>

 </web-app>