访问jsp页面时出现空指针异常，求大神解决
List中值是null,不知道怎么取到值。。。
JAVA CODE:
List listBrand = new ArrayList();
while(rs.next()){
BrandVO brand = new BrandVO();
brand.setId(rs.getInt("id"));
brand.setBname(rs.getString("name"));
listBrand.add(brand);
}
req.setAttribute("carList", rs.getInt("id"));
req.getRequestDispatcher("add_car.jsp").forward(req, resp)
jsp中代码：
<%
List<BrandVO> listBrand = (List) request.getAttribute("carList");
for(BrandVO brand : listBrand){
%>
<option><%=brand.getBname()%></option>
<% }%>
看样子你是使用的迭代器啊，你的rs中有值吗？先打个断点看看
req.setAttribute("carList", rs.getInt("id"));
改成 req.setAttribute("carList", listBrand);
打断点，调试一下，一步一步的查一下，看看在传值的时候哪个地方错了
<%
List listBrand = (List) request.getAttribute("carList");
if(listBrand!=null){
for(BrandVO brand : listBrand){
%>
<option><%=brand.getBname()%></option>
<% }}%>
package com.rentcar.service;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.catalina.Session;
import com.rentcar.vo.BrandVO;
public class AddCarServer extends HttpServlet{
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doPost(req, resp);
}
@Override
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection ct = DriverManager.getConnection("jdbc:mysql://localhost:3306/rent","root","123456");
Statement sta = ct.createStatement();
ResultSet rs = sta.executeQuery("SELECT * FROM tab_brand");
//PreparedStatement ps = ct.prepareStatement("SELECT * FROM tab_brand");
//ResultSet rs = ps.executeQuery();
List listBrand = new ArrayList();
while(rs.next()){
BrandVO brand = new BrandVO();
brand.setId(rs.getInt("id"));
brand.setBname(rs.getString("name"));
listBrand.add(brand);
}
req.setAttribute("carList",listBrand);
req.getRequestDispatcher("add_car.jsp").forward(req, resp);
} catch (Exception e) {
e.printStackTrace();
}
}
}
<%@page import="com.rentcar.vo.BrandVO"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
租车管理系统
</ul>
</div>
<div class="user_infor">
<span class="uesr_name">欢迎您！</span> <span>租车管理系统</span>
</div>
<div class="clr"></div>
</div>
<div class="base_content">
<div class="car_pay_content" style="border: none;">
<div class="car_dynamic_option">
<div class="user_infor_right">
<div class="user_dest_top">
<div class="dest_top_one"></div>
<div class="dest_top_two">
<h1>添加车辆信息</h1>
</div>
<div class="dest_top_three"></div>
<div class="clr"></div>
</div>
<div class="user_dest_content">
<ul>
<li><label><abbr title="required">*</abbr> 车辆品牌：</label>
<select>
<%
List<BrandVO> listBrand = (List) request.getAttribute("carList");
if(listBrand!=null){
for(BrandVO brand : listBrand){
%>
<option><%=brand.getBname()%></option>
<% }}%>
</select></li>
<li><label><abbr title="required">*</abbr> 车辆型号：</label> <select>
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
</select></li>
<li><label>大陆牌照：</label> <input type="text" /></li>
<li><label>香港牌照：</label> <input type="text" /></li>
<li><label>颜色：</label> <input type="text" /></li>
<li><label>所属门店：</label> <select>
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
</select></li>
<li><label><abbr title="required">*</abbr> 状态：</label> <select>
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
</select></li>
<div class="clr"></div>
</ul>
<div class="laye_form_botton">
<div class="save_button">
<span class="input_left"></span> <a><input type="submit"
value=" 新增车辆信息 " /></a> <span class="input_right"></span>
</div>
<div class="cancel_button">
<span class="input_left"></span> <a><input type="button"
value="取消"/></a> <span class="input_right"></span>
</div>
</div>
<!--laye_form_botton-->
</div>
<!--user_dest_content-->
<div class="user_dest_bottom">
<div class="dest_bottom_le"></div>
<div class="dest_bottom_ce"></div>
<div class="dest_bottom_ri"></div>
<div class="clr"></div>
</div>
</div>
<div class="clr"></div>
</div>
</div>
<div class="import_information">
<ul class="infor_one">
<li class="infor_one_text">重要提醒</li>
<li><a>今日订单数量<span class="red">( 10 )</span></a></li>
<li><a>今日用车数量<span class="red">( 4 )</span></a></li>
<li><a>今日还车数量<span class="red">( 20 )</span></a></li>
<li><a>本月车辆年检提醒<span class="red">( 30 )</span></a></li>
<li class="infor_month"><a>本月保险到期提醒<span class="red">(
10 )</span></a></li>
<li class="infor_one_text">常用工具</li>
<li class="infor_two_text"><a> <span class="icon_violate"></span>
<span class="icon_text">违章信息查询</span>
</a></li>
<li class="infor_two_text"><a> <span class="icon_plain"></span>
<span class="icon_text">航班信息查询</span>
</a></li>
<li class="infor_two_text"><a> <span class="icon_trail"></span>
<span class="icon_text">列车信息查询</span>
</a></li>
<li class="infor_two_text"><a> <span class="icon_user"></span>
<span class="icon_text">身份证查询</span>
</a></li>
<li class="infor_two_text"><a> <span class="icon_gps"></span>
<span class="icon_text">GPS导航</span>
</a></li>
</ul>
</div>
</div>
</div>
<div class="foot">
<p>版权所有(C)2009-2014 朗思科技</p>
</div>
你最好打个断点 调试一下，看的话很难看出来