Dish management system summary data transfer between jsp and servlet

The system is built based on MVC, and the most typical MVC pattern is the pattern of JSP + servlet + javabean .

Model (model) represents the core of the application (such as a list of database records).
View displays data (database records).
Controller (controller) processing input (writing database records)

The main knowledge used are:

1. The operation of the file upload class (add several jar packages) PS: mainly to display the menu photos here, you need to use the file upload

/********************Create a new file upload factory************************ ****************/
           Map<String,String> map = new HashMap<String,String>();
           //1. Create a disk file item factory object
           DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory ();
           //2. Create a core parsing class
           ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
           //3. Parse the request request and return a List request, the List collection stores the FileItem object
           List<FileItem> list1 = servletFileUpload .parseRequest(request);
           //Define a List collection
           String url = null;
           for (FileItem fileItem : list1) {
               // Determine whether it is a form item or a file upload item
               if(fileItem.isFormField()){
                   //Ordinary form item;
                   //Receive the value of the form parameter:
                   String name = fileItem.getFieldName();//Get the value of the name attribute of the form item
                   String value = fileItem.getString("UTF-8");//Get The value of the form item
                   System.out.println(name+" "+value);
                   // Store the data in the map collection
                   map.put(name, value);
                                                           }
           else{
               // File upload item
               //File upload function
               // Get the name of the file upload
               String fileName = fileItem.getName();
               if(fileName !=null && !"".equals(fileName)){
                   // Get the unique file name through the tool class
                   String uuidFileName = UploadUtils.getUUIDFileName(fileName);
                   //Get file upload data
                   InputStream is = fileItem.getInputStream();
                   //Get file upload path
                   String path = this.getServletContext().getRealPath("/upload");
                   // Just connect the input stream to the output stream
                   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();
               }
           }

2. Set the basic path in jsp

<%
String basePath = request.getScheme()+":"+"//"+request.getServerName()+":"+request.getServerPort()
+request.getServletContext().getContextPath()+"/";
%>

主程序： <form action="<%=basePath%>FoodDeleteServlet" method="post">

3. Data interaction between servlet and jsp

servlet to jsp

a. Redirection (PS: session data will not be lost immediately when it runs out)

        List<Food> list = (List<Food>) this.getServletContext().getAttribute("list");
       for(Food food:list){
           if(foodName.equals(food.getFoodName()))
           {
               //跳转到菜品查询
                    request.getSession().setAttribute("id", food.getFoodId());
                   request.getSession().setAttribute("foodName", food.getFoodName());
                   request.getSession().setAttribute("taste", food.getFoodTaste());
                   request.getSession().setAttribute("price", food.getFoodPrice());
                   request.getSession().setAttribute("description", food.getFoodDescrip());
                   request.getSession().setAttribute("url", food.getFoodPath());
                   food.getFoodDescrip();
               flag=1;
               break;
           }
       }
       request.getSession().setAttribute("flag", flag);

       response.sendRedirect(request.getContextPath()+"/showFoodList.jsp");

b. Relocation (PS: The data in the request is lost immediately when it runs out)

            for(Food u :foodList){
               if(u.getFoodId().equals(map.get("id"))||u.getFoodName().equals(map.get("foodName"))){
                   request.setAttribute("msg", "用户已经存在！");
                   request.getRequestDispatcher("/showFoodList.jsp").forward(request, response);
                   return ;
               }

c.jsp pass data to servlet

In the form of a form (see: data transfer between jsp and servlet )

Dish management system summary data transfer between jsp and servlet

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