在tomcat的server.xml中插入如下内容：
<Context path="/ch07" docBase="ch07" debug="0" reloadable="true" crossContext="true">
       <Resource name="jdbc/cn" auth="Container" type="javax.sql.DataSource"/>
    <ResourceParams name="jdbc/cn">
    <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://127.0.0.1:1433;DatabaseName=student</value>
    </parameter>
        <parameter>
          <name>username</name>
          <value>sa</value>
    </parameter>
     <parameter>
          <name>password</name>
        <value> </value>
     </parameter>
        <parameter>
      <name>maxActive</name>
      <value>20</value>
      </parameter>
    <parameter>
       <name>maxIdle</name>
       <value>10</value>
    </parameter>
    <parameter>
      <name>maxWait</name>
      <value>-1</value>
    </parameter>
       </ResourceParams>
    </Context>
用于获得连接的类：
package bole;
import java.sql.*;
import java.util.Properties;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;
public class DatabaseConn
{
    public static  Connection getConnection() throws Exception
    {
        try
        {
            Context initCtx = new javax.naming.InitialContext();
            Context envCtx=(Context)initCtx.lookup("java:comp/env");
            DataSource ds = (DataSource)envCtx.lookup("jdbc/bn");
            return ds.getConnection();
        }
        finally
        {
        }
    }
}
使用数据源的servlet:
package bole;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
import java.io.*;
public class DataSourceTestServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet 
{
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        // TODO Auto-generated method stub
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        try
        {
            Connection con=DatabaseConn.getConnection();
            Statement stmt = con.createStatement();
            //stmt.execute("select * from course");
            ResultSet rst = stmt.executeQuery("select * from course");
            while(rst.next())
            {
                out.println(rst.getString("id"));
                out.println(rst.getString("name"));
            }
            stmt.close();
            con.close();
        }
    }                       
}
可是运行时出现错误，东西比较多，麻烦各位了