对这个作业很大的迷惑

1。在前面我们的案例中，UploadUtils类只是用来处理文件的同名问题，所以我在里边只定义了 public static String getUUIDFileName(String fileName)
  {
 
  
   //将文件名的前面部分截取.jpg
   int idx=fileName.lastIndexOf(".");
  String content= fileName.substring(idx);
 String uuidFileName=  UUID.randomUUID().toString().replace("-", "")+content;
 return uuidFileName;
  }这么一个方法，也就是返回一个处理过的文件名。

我在添加菜品的servlet中，init方法里我定义了存放菜品的集合，然后再doGet方法里来写逻辑控制

package foodServlet;

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 java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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 foodInfo.FoodInfo;
import utils.UploadUtils;

/*
 * 菜品添加的servlet
 */
@WebServlet("/FoodAddServlet")
public class FoodAddServlet extends HttpServlet {
 @Override
 public void init() throws ServletException {
  List<Map<String,FoodInfo>> list = new ArrayList<Map<String,FoodInfo>>();
  this.getServletContext().setAttribute("list", list);
 }

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

  try {
   // 定义一个Map,用来存放添加页面中用户输入的所有控件对应的值
   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);
   //定义一个集合，用来存放口味数据
   List<String> taste=new ArrayList<String>();
   String url=null;
   //遍历FileItem集合，判断是表单项还是文件上传项
   for(FileItem fileItem:list)
   {
    if(fileItem.isFormField())
    {
     //普通表单项
     //接收表单项对应的值
     String name=fileItem.getFieldName();//获得表单项name的属性值
     String value=fileItem.getString("utf-8");//获得表单项的值
     //接收复选框的值
     if(name.equals("taste"))
     {
      String tasteValue=fileItem.getString("utf-8");
      taste.add(tasteValue);
       tasteValue=taste.toString().substring(1, taste.toString().length()-1);
      System.out.println(name+" "+ tasteValue);
      map.put(name, tasteValue);
     }else
     {
      map.put(name, value);
     }
    }else
    {
     //文件上传项
     //文件上传功能
     //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 uniqueFileName=UploadUtils.getUUIDFileName(fileName);
      //获得文件上传的数据
      InputStream is=fileItem.getInputStream();
      //获得文件上传的路径
      String path=this.getServletContext().getRealPath("/upload");
      //将输入流对接到输出流
       url=path+"\\"+uniqueFileName;
      OutputStream os=new FileOutputStream(url);
      int len=0;
      byte[] b=new byte[1024];
      while((len=is.read(b))!=-1)
      {
       os.write(b, 0, len);
      }
      os.flush();
      os.close();
      is.close();
     }
    }
    
   }
   //判断菜品ID是否存在
   List<Map<String,FoodInfo>> foodList=(List<Map<String,FoodInfo>>)this.getServletContext().getAttribute("list");
   for(Map<String,FoodInfo> food:foodList){
    if(food.get(map.get("id")).getFoodId().equals(map.get("id")))
    {
     request.setAttribute("msg", "该菜品已经存在，请重新添加");
     request.getRequestDispatcher("/myFile.jsp/addFood.jsp").forward(request, response);
     return;
    }
   
   }
   //封装数据到FoodInfo中
   FoodInfo food=new FoodInfo();
   food.setFoodId(map.get("id"));
   food.setFoodName(map.get("foodName"));
   food.setPicPath(url);
   food.setFoodPrice(map.get("price"));
   food.setDescription(map.get("description"));
   food.setFoodTaste(map.get("taste"));
   Map map1=new HashMap();
   map1.put(map.get("id"),food);
   //将菜品信息保存到集合中
   foodList.add(map1);
   for(Map<String,FoodInfo> fo:foodList){
    System.out.println(fo.get(map.get("id")));
   }
   this.getServletContext().setAttribute("list", foodList);
   //添加成功，跳转到展示页面
   response.sendRedirect(request.getContextPath()+"/myFile.jsp/showFoodList.jsp");
  } catch (FileUploadException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }

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

  doGet(request, response);
 }

}

请问我这个思路，和作业提供的思路不一样，那么会出现什么问题，我不太理解作业的思路是什么意思，意思是我们定义一个上传相关的类，里边定义增删改查的方法，然后再servlet中调用吗？