Spring MVC pass same object between controller

Question

In Spring MVC how do I pass an object between two controller methods? I have an update form and an updateController. In the controller I have 2 methods, one for fetching the

Answer 1

You have 3 options

1. Use @SessionAttributes to store the object in the session in between requests.
2. Use a @ModelAttribute annotated method to retrieve the object before each request
3. Write your own code and store it in the session (similair to 1 but more work on your part).

Option 1

1. Add the @SessionAttributes annotation to your controller class
2. Add the SessionStatus as a parameter to your update method and the setComplete() method when you are finished with the object

---

@SessionAttributes("emp")
public class EmployeeController {
@RequestMapping(value = "/editEmpFormSubmission.html", method = RequestMethod.POST)
public String editEmpFormSubmission(
    @RequestParam(value = "page", required = false) Integer page,
    @ModelAttribute("emp") Employee emp, BindingResult result,
    ModelMap model, HttpServletRequest request
    SessionStatus status) {
 // update changes in DB
 status.setComplete();
}    
} 

Option 2

1. Add the method which retrieves the object from the database and annotate it with @ModelAttribute
2. Cleanup your showEmpDetails method as it should only return a view name

---

public class EmployeeController {
    
    @ModelAttribute("emp")
    public Employee getEmployee(@RequestParam("empdId") Long id) {
        // Get employee using empId from DB
        return  emp;
    }
    
    @RequestMapping(value = "/showEmpDetail.html", method = RequestMethod.GET)
    public String showEmpDetails() {) {
        return "showEmpDetail";
    }
}

Option 3

1. In your methods add the HttpSession as an argument
2. In your showDetails method next to adding it to the model add it to the session
3. In your editEmpFormSubmission use the one from the session and copy all non-null fields to the object from the session and store that in the database.

I wouldn't go for option, I strongly would suggest option 1 especially including the setComplete() on the SessionStatus object for cleanup. You could also combine 1 and 2 (have a @ModelAttribute annotated method and still use @SessionAttributes.).

Answer 2

How can I make sure the same object is passed by view. I do not want to add the object as sessionAttribute since a user might modify many employees in a session

You could make a field in the object that is filled with a random number at the time of initial render and then store that object in the session. In the view you can map that field with a hidden input and now when user sends a request to edit action you can get that hidden field and fetch the original object from session by the number in the hidden field. That would resolve the multiple edits in different tabs conflict.