tomcat6.0如何配置数据库连接池

报错如下：

javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file:  java.naming.factory.initial

	at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:645)

	at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288)

	at javax.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:325)

	at javax.naming.InitialContext.lookup(InitialContext.java:392)

	at common.sqlHelper.DBTools.getConn(DBTools.java:22)

	at common.sqlHelper.DBTools.main(DBTools.java:74)

我的代码如下：

/**

 * 创建数据库连接池

 */

package common.sqlHelper;



import java.sql.*;

import javax.naming.Context;

import javax.naming.InitialContext;

import javax.sql.DataSource;



public class DBTools {



	private Connection conn;

	private ResultSet rs;

	private PreparedStatement ps;

	private DataSource ds;



	public Connection getConn() {



		try {

			Context ctx = new InitialContext();

			ds = (DataSource)ctx.lookup("java:comp/env/oracle");

			if(ds != null)

			{

				conn = ds.getConnection();

			}

		} catch (Exception e) {

			System.out.println("异常时手动连接数据库");

			e.printStackTrace();

			// 异常时手动连接数据库

			String url = "jdbc:oracle:thin:@localhost:1521:ORA9I";

			String name = "scott";

			String passwd = "tiger";

			try {

				Class.forName("oracle.jdbc.driver.OracleDriver");

				conn = DriverManager.getConnection(url, name, passwd);

			} catch (Exception e2) {

				// TODO: handle exception

				e.printStackTrace();

			}

		}

		return conn;

	}

	

	public void close()

	{

		if(rs != null){

			try {

				rs.close();

			} catch (SQLException e) {

				// TODO Auto-generated catch block

				e.printStackTrace();

			}

		}

		if(ps != null){

			try {

				ps.close();

			} catch (SQLException e) {

				// TODO Auto-generated catch block

				e.printStackTrace();

			}

		}

		if(conn != null){

			try {

				conn.close();

			} catch (SQLException e) {

				// TODO Auto-generated catch block

				e.printStackTrace();

			}

		}

	}

	public static void main(String[] args) {

		DBTools d = new DBTools();

		d.getConn();

	}

}

tomcat的server.xml中：

……

        -->

      </Host>

    </Engine>

  </Service>

  <!--

  		<context path="/TestLogin" doBase="E:\workspace2\WorkSpace\WorkSpace\TestLogin\WebRoot"

		 reloadable="true" workDir="E:\workspace2\WorkSpace\WorkSpace\TestLogin\work">

	-->

		<Resource name="oracle" 

		 auth="Container"

		 type="javax.sql.DataSource"

		 driverClassName="oracle.jdbc.driver.OracleDriver"

		 url="jdbc:oracle:thin:@localhost:1521:ORA9I"

		 username="scott"

		 password="tiger"

		 maxActive="100"

		 maxIdle="20"

		 maxWait="2000"

		/>

		<!--

		</context>

		-->

</Server>

web.xml中：

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.4" 

	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">

	

	<resource-ref>           

	    <description>DB Connection</description>           

	    <res-ref-name>jdbc/oracle</res-ref-name>           

	    <res-type>javax.sql.DataSource</res-type>           

	    <res-auth>Container</res-auth>           

  	</resource-ref>   

	

  <welcome-file-list>

    <welcome-file>index.jsp</welcome-file>

  </welcome-file-list>

</web-app>

在网上查了查 好像没什么错误 求助了