请教,关于JNDI的问题(100分)

最近在研究关于数据库的问题,写了一个程序,但是老连不上数据库,头疼啊,找了一下午,也没成功连接上
在netbean
总提示:
信息: AdminServlet: Error is processing add : com.wrox.begjsp.ch23.football.DataException: Cannot create JDBC driver of class '' for connect URL 'null'
2006-10-21 22:09:30 org.apache.catalina.core.ApplicationContext log
信息: AdminServlet: Error processing roster list : com.wrox.begjsp.ch23.football.DataException: Cannot create JDBC driver of class '' for connect URL 'null'
数据库的设置写在一个tomcat上下文文件ch13.xml,内容如下:

<Contextdo
Base=&quot;G:/hhd/java/netbeans/testch13/ch13/web&quot;
path=&quot;/ch13&quot;<?xml version=&quot;1.0&quot;
encoding=&quot;UTF-8&quot;?>

reloadable=&quot;true&quot;
>
<Resource name=&quot;jdbc/FootyDB&quot;
type=&quot;javax.sql.DataSource&quot;
auth=&quot;Container&quot;
/>
<ResourceParams name=&quot;jdbc/FootyDB&quot;>
<parameter>
<name>username</name>
<value>footy</value>
</parameter>
<parameter>
<name>password</name>
<value>footy</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>com.mysql.jdbc.Driver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:mysql://localhost:3306/footydb?autoReconnect=true</value>
</parameter>
</ResourceParams>

</Context>
web应用的目录是这样的
ch13/
src/
web/
WEB-INF/
lib/
ch13.xml的文件在ch13目录下
连接数据库的文件是:FootyJDBCHelper.java
package com.wrox.begjsp.ch23.football;
import java.sql.Connection;
import java.sql.SQLException;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

/**
*
* @author Administrator
*/
public class FootyJDBCHelper {

private DataSource _dataSource;
/** Creates a new instance of FootyJDBCHelper */
public FootyJDBCHelper() throws NamingException{
Context context = new InitialContext();
Context applicationEnv = (Context)context.lookup(&quot;java:comp/env&quot;
_dataSource = (DataSource)applicationEnv.lookup(&quot;jdbc/FootyDB&quot;
}

public Connection getConnection() throws SQLException
{
return _dataSource.getConnection();

}

}
事情就是这样,按照参考书上应该是没问题,但是就是报错?
高手指点指点,急急急!!!!!