tomcat 问题 ，哥们刚开始玩这个，结果郁闷了一天，谁帮偶解决啊！！！！！！！

server.xml中        <Context path="dbpool" docBase="dbpool" debug="0" reloadable="true">
        
  <Resource name="jdbc/dbpool" auth="Container"
            type="javax.sql.DataSource"/>
  <ResourceParams name="jdbc/dbpool">
    <parameter>
      <name>username</name>
      <value>root</value>
    </parameter>
    <parameter>
      <name>password</name>
      <value></value>
    </parameter>
    <parameter>
      <name>driverClassName</name>
      <value>org.gjt.mm.mysql.Driver</value>
    </parameter>
    <parameter>
      <name>url</name>
      <value>jdbc:mysql://127.0.0.1/guestbook?autoReconnect=true</value>
    </parameter>
    <parameter>
      <name>maxActive</name>
      <value>50</value>
    </parameter>
    <parameter>
      <name>maxIdle</name>
      <value>20</value>
    </parameter>
    <parameter>
      <name>maxWait</name>
      <value>10000</value>
        </parameter>
  </ResourceParams>
  
</Context>
web.xml中<?xml version="1.0" encoding="ISO-8859-1"?><web-app xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
    version="2.4">  <display-name>jervis</display-name>
  <description>
     jervis
  </description>
  
<resource-ref>
      <description>DB Connection</description>
      <res-ref-name>jdbc/dbpool</res-ref-name>
      <res-type>javax.sql.DataSource</res-type>
      <res-auth>Container</res-auth>
  </resource-ref></web-app>基本是按照tomcat的官方文档试着玩的
最后的test.jsp的用其他地方的
<%@page contentType="text/html;charset=gb2312"%>
<%@page import="java.sql.*"%>
<%@page import="javax.sql.DataSource"%>
<%@page import="javax.naming.*"%>
<html>
<body>
<%
 
     Context initContext = new InitialContext();
         Context envContext  = (Context)initContext.lookup("java:/comp/env");
         DataSource ds = (DataSource)envContext.lookup("jdbc/dbpool");
             
             out.print("aaa");
             
             //Connection conn = ds.getConnection("root","");
            
             Connection conn=null;
                          
             
             try{  
             conn = ds.getConnection();
              out.print("ccc");
         Statement stmt = conn.createStatement();  
         ResultSet rs = stmt.executeQuery("select * from content"); 
      
        while(rs.next())
        {    out.print(rs.getString(1)+" ");   
        
         } 
          rs.close(); 
          stmt.close();  
          conn.close();
      }
      catch(Exception e)
      {  out.print(e);}
      %>
      </body>
      </html>
结果是老是报错：
aaaorg.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class 'org.gjt.mm.mysql.Driver' 发现程序执行到conn = ds.getConnection();就挂了！
这是什么问题啊，郁闷啊！谁帮偶解决哈把，谢谢了！！！！！！！！