求助大神，数据池连接报错

这个问题已经纠结了一个礼拜了 求大神帮忙 谢谢了
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 com.pb.news.dao.BaseDao.getConnection(BaseDao.java:33)
at com.pb.news.dao.BaseDao.executeSQL(BaseDao.java:64)
at com.pb.news.dao.impl.NewsDaoImpl.getNewsList(NewsDaoImpl.java:18)
at com.pb.news.dao.test.test.main(test.java:13)
Exception in thread "main" java.lang.NullPointerException
at com.pb.news.dao.BaseDao.executeSQL(BaseDao.java:66)
at com.pb.news.dao.impl.NewsDaoImpl.getNewsList(NewsDaoImpl.java:18)
at com.pb.news.dao.test.test.main(test.java:13)
代码

package com.pb.news.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;






//基类：数据库操作通用类
public class BaseDao {
protected Connection conn;
protected PreparedStatement ps;
protected Statement stmt;
protected ResultSet rs;


// 获取数据库连接
public Connection getConnection() {
try {
//初始化上下文
Context cxt=new InitialContext();
//获取与逻辑名相关联的数据源对象
DataSource ds=(DataSource) cxt.lookup("java:comp/env/jdbc/news");
conn=ds.getConnection();
} catch (NamingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}

// 增删改 delete from news_detail where id=? and title=?
public int executeUpdate(String sql, Object[] params) {
int updateRows = 0;
getConnection();
try {
ps=conn.prepareStatement(sql);
//填充占位符
for(int i=0;i<params.length;i++){
ps.setObject(i+1, params[i]);
}
updateRows=ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
return updateRows;
}

// 查询
public ResultSet executeSQL(String sql,Object[] params) {
getConnection();
try {
ps=conn.prepareStatement(sql);
//填充占位符
for(int i=0;i<params.length;i++){
ps.setObject(i+1, params[i]);
}
rs=ps.executeQuery();
} catch (SQLException e) {
e.printStackTrace();
}
return rs;
}

// 关闭资源
public boolean closeResource() {
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
if(ps!=null){
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
if(stmt!=null){
try {
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
return true;
}

}



配置文档


<ReSource
name="jdbc/news"
auth="Container"
type="javax.sql.DataSource"
password="sxy"
username="scott"
driverClassName="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@localhost:1521:orcl"
maxActive="100"
maxIdle="30"
maxWait="5000"

/>