Spring Boot—10ModelAndView, Model, and @ModelAttribute annotations

package com.bee.sample.smartmap.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

import com.bee.sample.ch3.entity.User;
import com.bee.sample.ch3.service.UserService;

@Controller
@RequestMapping("/model")
public class ModelAndViewController {
    
    @Autowired UserService userService;
    /**
     * A beetl template test. Because the view extension name is btl
     * @param userId
     * @param model
     * @return
     */
    @GetMapping(path = "/{userId}/get.html")
    public String getUser(@PathVariable Long userId,Model model) {
         User userInfo =   userService.getUserById(userId);
          // model.addAttribute(userInfo); does the same as the following line, but there are potential problems 
         model.addAttribute("user" , userInfo);
          return "/userInfo.html" ;
    }
    /**
     * Use freemaker template test, freemaker will look for /userInfo.ftl template
     * @param userId
     * @param view
     * @return
     */
    @GetMapping(path = "/{userId}/get2.html")
    public ModelAndView getUser2(@PathVariable Long userId,ModelAndView view) {
         User userInfo =  userService.getUserById(userId);
         //model.addAttribute(userInfo);
         view.addObject("user", userInfo);
         view.setViewName("/userInfo");
         return view;
    }
    
    
}

package com.bee.sample.smartmap.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import com.bee.sample.ch3.controller.form.OrderPostForm;
import com.bee.sample.ch3.service.UserService;

@Controller
@RequestMapping("/modelattribute")
public class ModelAttributeController {
    @Autowired UserService userService;
    /**
     * Public in the Controller method, call this method before calling the method.
     * @param id
     * @param model
     */
    @ModelAttribute
    public  void findUserById (athPathVariable Long id, Model model)
        model.addAttribute("user", userService.getUserById(id));
    }
    
    @GetMapping(path = "/{id}/get.json")
    @ResponseBody
    public String getUser(Model model) {
        System.out.println(model.containsAttribute("user"));
        return "success";
    }
    
}