Unable to populate modelAttribute in spring

Question

I am unable to get the ModelAttribute for second request. My first request is initForm() method I prepared Command object and able to display the command in jsp.

Through initForm() I am populating command and that command I want in editForm when I will do ajax call.

Here is my spring form

<form:form method="POST" action="addstudentdetails.htm" commandName="command">
 Ignore what is inside this 

 Name: Shoaib Age:23  <a href="#" onclick="editstudentdetails(1,0)">edit</a>

</form:form>

My ajax request:

function editStudentDetails(studentId,index){
       $.ajax(
        {url:"editstudentdetails.htm",
         method:"GET",
         data:{"action":"edit","id":studentId,"index":index},
            success: function(data) {
                   jQuery("#studentDetailsDiv").html(data)
            }

        }

      )
   }

In editStudentDetails() method I have method ajax call to go editForm() of the controller.

Here is my controller:

@Controller

public class StudentDetailsController {

@Autowired
private StudentDetailsDAO studentDetailsDAO;

@RequestMapping(value="/studentdetails.htm",method = RequestMethod.GET)
public String initForm(HttpServletRequest request,ModelMap map){
    String action=request.getParameter("action");
    StudentDetailsCommand command=new StudentDetailsCommand();
    System.out.println("in controller"+action);
    command.setStudents(studentDetailsDAO.findAll());
    map.addAttribute("command", command);

    return "studentdetails";
}

@RequestMapping(value="/editstudentdetails.htm",method = RequestMethod.GET)
public String editForm(ModelMap map,HttpServletRequest request){
  map.addObject("index", request.getParameter("index"));
    StudentDetailsCommand command=(StudentDetailsCommand)map.get("command");
  System.out.println(command);
  System.out.println(command.getStudents());//NullPointerException here.
  map.addObject("command", command);
    return "studentdetails";
 }
}

Even tried @ModelAttribute("studentDetailsCommand") but didn't worked.

I am new to Spring 3.0 and I followed all solutions which are given here but nothing worked.Can anyone help me out please?

What is the second request? What model attribute are you talking about? — Sotirios Delimanolis, Jan 11 '14 at 19:00
second request made by ajax call which comes in editForm method and i getting it through map.get("xxx") — Shoaib Chikate, Jan 11 '14 at 19:01
When i click on edit link it is ajax request which i send.Let me add that ajax method too. — Shoaib Chikate, Jan 11 '14 at 19:09

score 1 · Accepted Answer · edited May 23 '17 at 10:25

1

Model attributes only exist during the life cycle of one HttpServletRequest. Consider reading my answer here.

In your initForm method, you do the following

map.addAttribute("command", command);

this add an attribute named command to the model attributes. This attribute will eventually find its way into the HttpServletRequest attributes and be available to your JSP. In here

<form:form [...] modelAttribute="studentDetailsCommand" commandName="command">

first of all, modelAttribute and commandName have the same purpose, ie. to find an attribute in the model. If you remove commandName you will get an Exception because there is no model attribute named studentDetailsCommand. Here your commandName's value is overwriting your modelAttribute's value.

When the Servlet container is finished rendering your JSP, the rendered content is sent as the body of the HTTP response. At this point, the request has been handled and the HttpServletRequest and the model attributes are garbage collected.

When you send your new request through AJAX, there is no longer any model attribute named studentDetailsCommand (there actually never was).

Consider using Flash Attributes.

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answered Jan 11 '14 at 19:38

Sotirios Delimanolis

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So can u tell me how i can solve my problem.Should i remove my modelAttribute from form or change it to "command".Please check my updated question which i followed your suggestion. – Shoaib Chikate Jan 11 '14 at 19:44
@ShoaibChikate Yes, use either `modelAttribute` or `commandName`, not both. As I stated in my answer, look into flash attributes. – Sotirios Delimanolis Jan 11 '14 at 19:53
What happening here is initForm is populating attributes and when another request gets starts then command is not their in the modelMap....so shud i add command as flashAttribute in initForm() – Shoaib Chikate Jan 11 '14 at 19:56
@ShoaibChikate That will make it available in the next request. If that is what you want to do, then yes. – Sotirios Delimanolis Jan 11 '14 at 19:57
Added redirectAttribute in initForm but i m unable to access in jsp. – Shoaib Chikate Jan 11 '14 at 20:05
@ShoaibChikate Unable to access what? – Sotirios Delimanolis Jan 11 '14 at 20:07
reDirect.addFlashAttribute("command",command) this i added in initForm but in studentDetails.jsp when i print ${command} gives nothing. – Shoaib Chikate Jan 11 '14 at 20:11
@ShoaibChikate Please edit your question with what you are currently trying. – Sotirios Delimanolis Jan 11 '14 at 20:24
I solved by storing modelAttribute as in SessionAttribute so it is available for me for my next request. You can update your answer so i can accept it according – Shoaib Chikate Jan 11 '14 at 20:29
1

@ShoaibChikate That's what `RedirectAttributes` and `FlashMap` does already. The `RedirectAttributes` stores your flash attributes in a `ModelMap` which is merged with the `HttpServletRequest` attributes. That `ModelMap` is also used to generate a `FlashMap` which is stored in the `HttpSession` and retrieved in the next request. – Sotirios Delimanolis Jan 11 '14 at 20:33
Ok bro thanks for your time and help.Learnt new concept about ReDirectAttributes. – Shoaib Chikate Jan 11 '14 at 20:36
Hope this question and answer helps many user with same requirement. – Shoaib Chikate Jan 11 '14 at 20:40

Unable to populate modelAttribute in spring

1 Answers1