关于 JNDI

os:W7
tomcat 7.0用JNDI连接mysql数据库时，发现如下错误。。 求救于储大神
附
-------------------------------------------meta-inf/content.xml-----------------------------------------------<?xml version='1.0' encoding='utf-8'?><Context> <Resource auth="Container"
driverClassName="com.mysql.jdbc.Driver"
maxActive="100" maxIdle="40" maxWait="12000"
name="jdbc/Guestbook" username="root" password="123123"
type="javax.sql.DataSource" 
url="jdbc:mysql://localhost:3306/javabook?characterEncoding=UTF-8" /></Context>
---------------------------------------------web-inf/web.xml--------------------------------------------------
<resource-ref>
<description>DB Connection</description>
<res-ref-name>jdbc/Guestbook</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>----------------------------------------------- testDB.jsp ---------------------------------------------------
<%@ page language="java" import="java.util.*,javax.naming.*,java.sql.*,javax.sql.*" pageEncoding="UTF-8"%>
<%      
Context ctx = new InitialContext();        
String strLookup = "java:comp/env/jdbc/Guestbook";   
DataSource ds = (DataSource)ctx.lookup(strLookup);  
Connection con = ds.getConnection();  
if (con != null){  
out.print("success");  
   }else{  
out.print("failure");  
}         
%>--------------------------------------------------错误信息----------------------------------------------------
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: javax.servlet.ServletException: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null'
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root cause javax.servlet.ServletException: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null'
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:911)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:840)
org.apache.jsp.testDB_jsp._jspService(testDB_jsp.java:98)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root cause ………………