Day25SSM's SpringMVC method return value type***

Introduction to the return value of the processor

• (1) Servlet returns the result to the browser
  Forwarding: with data
  Redirection: without data
  Asynchronous: json data is sent to the js of the page, js organization label display
  Servlet里面编写响应浏览器的代码都要调用response
• (2) The springmvc method has designed a variety of return value types
  "ModelAndView
  " void
  "String: request forwarding, redirection, json data

The return value of the processor-ModelAndView

• (1) ModelAndView is a model view provided by SPringMVC
• (2) Function
  Set data addObject (key, value)
  setting page setViewName (logical view) is the name of the file

@Controller
public class Demo02ReturnController {
    
    
    //public 返回值类型 方法名(参数类型 参数名){}
    @RequestMapping(path = "demo01.action",method = {
    
    RequestMethod.POST,RequestMethod.GET})//回显页面
    public ModelAndView test01(){
    
    //
        Person p1 = new Person(1,"jack","1234");
        Person p2 = new Person(2,"rose","1234");
        List<Person> list = new ArrayList<Person>();
        list.add(p1);
        list.add(p2);

        //使用ModelAndView实现请求转发
        ModelAndView mv = new ModelAndView();
        mv.addObject("list",list);
        mv.setViewName("demo04_update_persons");//前缀+逻辑视图+后缀
        //物理视图 真正的文件地址 /WEB-INF/jsp/demo04_update_persons.jsp
        //物理视图 = 前缀+逻辑视图+后缀
        return mv;
    }
}

The return value of the processor-void

• (1) Write void as the return value type of the method.
  At this time, write request as the parameter, call request with setting parameters and request forwarding or redirection
• (2) Background code
• (3) Does not reflect the advantages of springmvc

Demo02ReturnController

    @RequestMapping(path="demo02.action",method = {
    
    RequestMethod.GET,RequestMethod.POST})
    public void test02(HttpServletRequest req, HttpServletResponse resp)throws Exception{
    
    
        //请求转发
        req.setAttribute("name","请求转发");
        req.getRequestDispatcher("demo05.jsp").forward(req,resp);
    }

The return value of the processor-String

• (1) The method return value type is written on the String
  method to return the page name
• (2) What if you carry data?
  Method parameters are written on Model, which is less View than ModelAndView

req.setAttriibute(key,val)
req....forward(req,resp)

》Model is a model class provided by SpingMVC, this class does not need to create objects by itself, the system automatically creates

• (3) Model role
  Model can be used to pass parameters to the page
• (4) Background code
  model.addAttribute("item", item);

  @RequestMapping(path="demo03.action",method = {
    
    RequestMethod.GET,RequestMethod.POST})
    public String test03(Model model){
    
    
        //Model 可以设置数据，自动由视图解析器带到页面
        model.addAttribute("data","wHelloWord");
        return "success"; //逻辑视图 文件名
    }

The return value of the processor-String-forwarding and redirection

• (1) What is a logical view and a physical view. The
  page name is called a logical view, not a real page address,
  but it can be spliced ​​by a view resolver to get the real page address, that is, the physical view
• (2) The return value can add instructions
  "1: forward request forwarding
  forward instruction: physical view
  " 2: redirect redirection
  redirect instruction: project access path + physical view
  特点：视图解析器不对指令后的内容拼接前缀与后缀
• (3) Instructions can also access controller methods

 @RequestMapping(path="demo04.action",method = {
    
    RequestMethod.GET,RequestMethod.POST})
    public String test04(Model model){
    
    
        //Model 可以设置数据，自动由视图解析器带到页面
        model.addAttribute("data","wHelloWord");
        //return "forward:/WEB-INF/jsp/success.jsp"; //
        //return "redirect:http://www.baidu.com"; //外网
        //return "redirect:demo05.jsp"; //
        return "redirect:demo01.action"; //
    }