如何从控制器返回对象列表并使用JQuery显示它们（Spring MVC，ajax）

Question

First, this is my controller:

@Controller
public class MainController {
   @Autowired
   SqlSession sqlSession;
   @Autowired
   Message messageVO;


@RequestMapping(value="getMessages", method=RequestMethod.GET)
public @ResponseBody List<Message> getMessages(HttpSession session){
    JbuserDAO dao = sqlSession.getMapper(JbuserDAO.class);
    List<Message> inboxList = null;
    String logedinUserId = (String) session.getAttribute("loginId");
    inboxList = dao.getInboxList(logedinUserId);
    System.out.println(inboxList);       //I do get the list here so it's not sql problem. I think.
    return inboxList;
}

and this is my JQuery:

$(function(){
   viewingInbox();
   $("#viewInbox").on('click', function(){
        viewingInbox();
    });
  });


function viewingInbox(){

   $.ajax({
        url: "getMessages"
      , method: "GET"
      , dataType: "JSON"
      , contentType: "application/json; charset=UTF-8"
      , success: function(obj){
        alert(obj.inboxList);      //I get undefined here
        messageInbox(obj);
      }
  });
}


function messageInbox(obj){
   var list = '<div>';
   $(obj.inboxList).each(function(i, item){
       list = list + '<article class="media">'
                  + '<span class="pull-left"><input type="checkbox" class="checkboxes"></span>'
                  + '<span class="pull-left thumb-sm"><img src="resources/images/a2.png" alt="..."></span>'
                  + '<div class="media-body">'
                  + '<div class="pull-right media-xs text-center text-muted">'
                  + '<strong class="h4">12:18</strong><br></div>'
                  + '<a href="#" class="h4">123'+item.sendidjbuser+'</a>'
                  + '<small class="block m-t-sm">'+item.message+'</small></div></article>'
   });
      list = list + '</div>';
      alert(list);               //here I get only <div></div>
      $("#inboxDiv").html(list);
      alert("messageInbox end");
}

What I'm trying to do is to get saved messages from DB and return them as a list of Message VO I made and then print them out on jsp. I thought this was the way to do it but I don't think I'm getting the list from the controller. I tried putting alert(message) inside the each statement, and it didn't work; no alert messages. That means I'm not getting the list from the controller. Am I missing something?

I jave json-databind dependency added, but that's everything I have concerning json.

I only learned Strut2 for a month and only recently started using Spring so I must have made stupid mistake I don't know. Please tell me what that is. Thanks in advance.

Answer 1

Problem solved. Unlike Struts2, I didn't have to do like this:

$(obj.inboxList).each(function(i, item){

I think in Struts2 I had to put obj.inboxList because on the action side there are getter and setters.

In Spring, there are no getter and setters so maybe, really maybe because I'm just guessing here, that's why just using obj works:

$(obj).each(function(i, item){

Answer 2

You can use ResponseEntity as return element and can also convert your list to json list so that jquery can interpret it as iterative element.

    @RequestMapping(value="getMessages", method=RequestMethod.GET)
    public ResponseEntity<String> getMessages(HttpSession session){
        JbuserDAO dao = sqlSession.getMapper(JbuserDAO.class);
        List<Message> inboxList = null;
        String logedinUserId = (String) session.getAttribute("loginId");
        inboxList = dao.getInboxList(logedinUserId);


  com.google.gson.Gson gson = new GsonBuilder().disableHtmlEscaping().create();
        String jsonString = gson.toJson(inboxList);
        HttpHeaders responseHeaders = new HttpHeaders();
        responseHeaders.add("Content-Type", "text/html; charset=utf-8");
        return new ResponseEntity<String>(jsonString, responseHeaders, HttpStatus.CREATED); 


    }

This way you will definitely get list of your message as you want. PS: i haven't gone through your rest of the code. But things like the following should work:

success: function(obj){

 $.each(obj, function(index) {
            alert(obj[index].sendidjbuser);
            alert(obj[index].message);
        });


      }

Answer 3

You can add Jackson to your classpath or add dependencies to maven and Spring Mvc convert your list to json. You only need add parameter to @RequestMapping produces="application/json", in your case it look @RequestMapping(value="getMessages", method=RequestMethod.GET, produces="application/json"), also parameter produces unnecessary but recommended. And you not need any edit in your controller.