Spring MVC处理方法返回值过程解析

@RequestMapping("/threadRequest*")
  public ModelAndView threadRequest(){
    ModelAndView mv=new ModelAndView();
    mv.setViewName("index");
    mv.addObject("user","王五");
    return mv;
  }

@RequestMapping("/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; 
  }

@RequestMapping("/RequestMethod")
  public String index(Model model) {
    String retVal = "user/index";
    List<User> users = userService.getUsers();
    model.addAttribute("users", users);

    return retVal;
  }

@RequestMapping("/index")
  public void firstRequest(HttpServletRequest request, HttpServletResponse response,HttpSession session) throws ServletException, IOException {

    UserInfo info=new UserInfo();
    info.setUser_id(1);
    info.setUser_name("张三");
    /**
     * Json格式传递
     */
    response.setCharacterEncoding("UTF-8");
    String value=JSON.toJSONString(info);
    response.getWriter().write(value);
  }

@RequestMapping("/fourthRequest")
  @ResponseBody  //响应体返回数据时，除了手动装换JSON格式字符串以外可以使用jackson
  public Object fourthRequest(){
    List<UserInfo> userList=new ArrayList<>();
    UserInfo info=new UserInfo();
    info.setUser_id(1);
    info.setUser_name("张三");
    UserInfo info2=new UserInfo();
    info2.setUser_id(2);
    info2.setUser_name("李四");
    userList.add(info);
    userList.add(info2);
    return userList;
  }