Detailed explanation of the seven return methods supported by spring mvc

This article mainly introduces the detailed explanation of the optional types of SpringMVC Controller return values. Spring MVC supports the following return methods: ModelAndView, Model, ModelMap, Map, View, String, void. If you are interested, you can learn more

spring mvc supports the following return methods: ModelAndView, Model, ModelMap, Map, View, String, void.

ModelAndView

@RequestMapping("/hello")
  public ModelAndView helloWorld() { 
    String message = "Hello World, Spring 3.x!";
    return new ModelAndView("hello", "message", message);
  }

Through ModelAndViewConstruction methodYou can specify the name of the returned page, or you can jump to the specified page through the setViewName() method

Map

@RequestMapping("/demo2/show") 
  public Map<String, String> getMap() { 
    Map<String, String> map = new HashMap<String, String>(); 
    map.put("key1", "value-1"); 
    map.put("key2", "value-2"); 
    return map; 
  }

In the jsp page, the value can be obtained directly through ${key1}. map.put() is equivalent to the request.setAttribute method.

View

You can return to pdf excel, etc. I don’t know the details yet.

String

Specify the returned view page name, which can be accessed by combining the set return address path and adding the page name suffix.

Note: If the method declares the annotation @ResponseBody, the return value will be output directly to the page.

@RequestMapping(value="/showdog")
  public String hello1(){
    return "hello";
  }

@RequestMapping(value="/print")
  @ResponseBody
  public String print(){
    String message = "Hello World, Spring MVC!";
    return message;
  }

Example of returning json (using Jackson):

@RequestMapping("/load1")
  @ResponseBody
  public String load1(@RequestParam String name,@RequestParam String password) throws IOException{
    System.out.println(name+" : "+password); 
    //return name+" : "+password;
    MyDog dog=new MyDog();
    dog.setName("小哈");dog.setAge("1岁");dog.setColor("深灰");
    ObjectMapper objectMapper = new ObjectMapper();
    String jsonString=objectMapper.writeValueAsString(dog);
    System.out.println(jsonString);
    return jsonString;
  }

void

If the return value is empty, respond The view page corresponds to the access address

@RequestMapping("/index")
  public void index() {
    return;
  }

and the corresponding logical view is named "index"

Summary:

1. Use String The return value type of the request processing method is a relatively general method, so that the returned logical view name will not be bound to the request URL, which has great flexibility, and the model data can be controlled through ModelMap.

2. When using void, map, or Model, the real URL of the corresponding logical view name returned is: prefix + view name + suffix.

3. Using String, the view name returned by ModelAndView can not be bound to the requested URL, and ModelAndView can set the returned view name.

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