求助:连接池问题! 感谢高手了!

工作环境:WinXP+Tomcat5.5.16在server.xml中加入了:
<Context path="/quickstart" docBase="quickstart">
    <Resource name="jdbc/quickstart" scope="Shareable" type="javax.sql.DataSource"/>
    <ResourceParams name="jdbc/quickstart">
        <parameter>
            <name>factory</name>
            <value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
        </parameter>
     
        <parameter>
            <name>driverClassName</name>
            <value>com.microsoft.jdbc.sqlserver.SQLServerDriver</value>
        </parameter>
         <parameter>
            <name>url</name>
            <value>jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=CAT</value>
        </parameter>
        <parameter>
            <name>username</name>
            <value>sa</value>
        </parameter>
        <parameter>
            <name>password</name>
            <value>1</value>
        </parameter>        <parameter>
            <name>maxWait</name>
            <value>30</value>
        </parameter>
        <parameter>
            <name>maxIdle</name>
            <value>10</value>
        </parameter>
        <parameter>
            <name>maxActive</name>
            <value>1</value>
        </parameter>
    </ResourceParams>
</Context>在WEB-INF文件夹下有web.xml:
<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd"><web-app><resource-ref>
<description>connectDB test</description>
<res-ref-name>jdbc/quickstart</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
 <ResourceLink global="jdbc/quickstart" name="jdbc/quickstart" type="javax.sql.DataSource"/></web-app>有测试文件:
<%@ page import="java.sql.*"%>
<%@ page import="javax.naming.*"%>
<%@ page import="javax.sql.*"%>
<%
       Context initCtx = new InitialContext();
       out.println("BBB::get jndi ok");
       out.println("BBB::get datasource");
       DataSource datasource = (DataSource) initCtx.lookup("java:comp/env/jdbc/quickstart");
      out.println("BBB::get datasource OK");
       out.println("BBB::get connection");
       out.println("BBB::get connection");
       Connection conn = datasource.getConnection();
       out.println("BBB::get connection OK"+conn);
       Statement stm = conn.createStatement();
       out.println("get stm OK");
       String sql = "select * from CAT";
       ResultSet rs = stm.executeQuery(sql);
       while(rs.next()){
        out.println(rs.getString(1));
        out.println("\n");
         out.println(rs.getString(2));
       }     
%>显示结果:
org.apache.jasper.JasperException: Exception in JSP: /a.jsp:1916: 
17:        out.println("BBB::get connection");
18: 
19:        Connection conn = datasource.getConnection();
20: 
21:        out.println("BBB::get connection OK"+conn);
22: Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(root cause javax.servlet.ServletException: Cannot create JDBC driver of class '' for connect URL 'null'
root cause org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null'
请高手们指点,感谢了!