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javaspringspring-mvccontrollermodelattribute

Unable to populate modelAttribute in spring

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?

Solution

  • 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.

    Related: