如图所示，为啥会提示空指针异常还有taste为啥出现两次！

package com.imooc.servlet;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.FileUploadException;

import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import org.apache.commons.fileupload.servlet.ServletFileUpload;

import com.imooc.bean.Food;

import com.imooc.utils.UploadUtils;

/**

 * 保存菜品的Servlet 

 */

public class SaveFoodServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

//数据接收

//文件上传的基本操作

try{

//定义一个map集合用于保存接收到的数据

Map<String,String> map = new HashMap<String,String>();

//1创建一个磁盘文件项工厂对象

DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();

//2.创建一个核心解析类

ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);

//3.解析request请求，返回的是list集合，list集合中存放的是FileItem对象；

List<FileItem> list = servletFileUpload.parseRequest(request);

//定义一个list集合，用与保存口味

List<String> tasteList = new ArrayList<String>();

String url = null;

//4.遍历集合

for (FileItem fileItem : list) {

//判断是表单项还是文件上传项

if(fileItem.isFormField()){

//普通表单项

//接收表单项参数值

String name = fileItem.getFieldName();

String value = fileItem.getString("utf-8");

System.out.println(name+" "+value);

//接收复选框数据

if("taste".equals(name)){

String tasteValue = fileItem.getString("utf-8");

//接收到一个值，将这个值存入到tastelist中去

tasteList.add(tasteValue);

tasteValue = tasteList.toString().substring(1, tasteList.toString().length()-1);

System.out.println(name+" "+tasteValue);

//将爱好的数据存入发哦map集合中去

map.put(name, tasteValue);

}else{

//将数据存入到map集合中

map.put(name,value);

}

}else{

//文件上传项

//获得文件上传的名称

String fileName = fileItem.getName();

if(fileName !=null && !"".equals(fileName)){

//通过工具类获得唯一文件名

String uuidFileName = UploadUtils.getUUIDFileName(fileName);

//获得文件上传数据

InputStream is = fileItem.getInputStream();

//获得文件的上传路径

String path = this.getServletContext().getRealPath("/upload");

//将输入流对接输出流

url = path+"\\"+uuidFileName;

OutputStream os = new FileOutputStream(url);

int len = 0;

byte[] b = new byte[1024];

while((len = is.read(b))!=-1){

os.write(b,0,len);

}

is.close();

os.close();

}

}

}

System.out.println(map);

//封装数据到food中

Food food = new Food();

food.setId(map.get("id"));

food.setName(map.get("name"));

food.setPrice(map.get("price"));

food.setTaste(map.get("taste"));

food.setDescription(map.get("description"));

food.setPath(url);

//将菜品信息存入到list集合中

List<Food> foodList = (List<Food>) this.getServletContext().getAttribute("list");

//检验用户名

for(Food f:foodList){

if(f.getName().equals(map.get("name"))){

request.setAttribute("mag", "该菜品已经注册！");

request.getRequestDispatcher("").forward(request, response);

}

}

foodList.add(food);

for (Food food2 : foodList) {

System.out.println(food2);;

}

this.getServletContext().setAttribute("list", foodList);

//注册成功后，跳转登录页面

request.getSession().setAttribute("foodName", food.getName());

response.sendRedirect(request.getContextPath()+"");

}catch(FileUploadException e){

e.printStackTrace();

}

}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

doGet(request, response);

}

}

id21

name2121

taste不辣

taste不辣

price222

description222

{id=21, price=222, description=222, name=2121, taste=不辣}

一月 20, 2018 7:31:46 下午 org.apache.catalina.core.StandardWrapperValve invoke

严重: Servlet.service() for servlet [SaveFoodServlet] in context with path [/food_management] threw exception

java.lang.NullPointerException

at com.imooc.servlet.SaveFoodServlet.doGet(SaveFoodServlet.java:106)

at com.imooc.servlet.SaveFoodServlet.doPost(SaveFoodServlet.java:128)