如何从 controller 到 Ajax 调用返回列表并成功打印？

Question

This is the pattern of the object I'm getting when I printed out my list value from rest controller.

[
   {
    "name": "Jon",
    "isUser": true
   },
   {
    "name": "Ween",
    "isUser": false
   }

]

but the problem is I dont know how can I get this value to my ajax call. I need that values for further work. But whenever I'm calling this controller my ajax return error 500 . this is my rest controller:

    @RequestMapping(value = "/getusers",  method = RequestMethod.GET)
    public List userShow(HttpServletRequest request, Model model) {

        List userlist = new ArrayList();
        try{
            userlist = JSONArray.fromObject(userService.getUserList());
            System.out.println(userlist);
        }catch (Exception e){
            logger.error(e);
        }
        return  userlist;
    }

I can clearly see the list of the printed userList from system.out but i'm not sure why these values are not going in the ajax call . Maybe I've to change the return of my function, I've given list as I want my data as the provided data I have given in the first part of the question. and my ajax call:

    $.ajax({
          type: "GET",
          url: "/getusers",
          success: function (response) {
           console.log(response);
           if(response === true) {
                  user = true;
             }
             else{
                 user = false;
              errorShow = "error getting values";
          }
      },
      async: false
  });

when this url hits, values are seen in the controller but in the console.log i see

GET http://localhost:3000/getusers 500

error. How can I get those values in the response section?

Answer 1

I think you are using @Controller annotation at the class level. If you use @RestController you will not have to write @Responsebody explicitly.

Also instead of @RequestMapping(value = "/getusers", method = RequestMethod.GET) you can use new method annotations like so. @GetMapping("/getusers")

Answer 2

If you really want to return the List you can use ResponseEntity like this:

@RequestMapping(value = "/getusers", method = RequestMethod.GET)
public ResponseEntity <List> userShow(HttpServletRequest request, Model model) {

    List userlist = new ArrayList();
    try {
        userlist = userService.getUserList();
        System.out.println(a);
    } catch (Exception e) {
        logger.error(e);
    }

    URI uri = ServletUriComponentsBuilder.fromCurrentRequest().path("/").buildAndExpand("").toUri();
    return ResponseEntity.created(uri).body(userlist);
}

Notice that I got rid of the JSONArray.fromObject() because ResposneEntity will take of converting the List into JSON for you. Also it's preferred to specify the List type, for example: List<User>

Answer 3

Just use @Responsebody annotation on method level and you don't have to convert list to array anymore. Return the list directly.

Change

JSONArray.fromObject(userService.getUserList())

To

userService.getUserList()