Question

I have a problem with the my Controller code. GET works fine (both empty form + form populated from db), POST works fine only for creating new object, but doesn’t work for editing. Part of my @Controller class:

    @RequestMapping(value = "/vehicle_save.html", method = RequestMethod.GET)
public String setUpForm(@RequestParam(value="id", required = false) Long id, ModelMap model) {
    Vehicle v;
    if (id == null) {
        v =  new Vehicle();
    } else {
        v = vehicleManager.findVehicle(id);
    }
    model.addAttribute("vehicle", v);
    return "vehicle_save";
}

@RequestMapping(value = "/vehicle_save.html", method = RequestMethod.POST)
public String save(@ModelAttribute("vehicle") Vehicle vehicle, BindingResult result, SessionStatus status) {
    vehicleValidator.validate(vehicle, result);
    if (result.hasErrors()) {
        return "vehicle_save";
    } 
    if(vehicle.getId() == null) {
        vehicleManager.createVehicle(vehicle);  
    } else {
        vehicleManager.updateVehicle(vehicle);  
    }
    status.setComplete();
    return "redirect:vehicle_list.html";
}

The first method creates a vehicle object (including its ID). But the second method gets the same object without the ID field (set to null).

What could I do: manually set vehicle.setID(id from parameters) and then save it to database. This causes JPAOptimisticLockException + I don’t like that solution.

Is there a way to pass my Vehicle object with ID to the second method? BTW, I would like to avoid adding hidden ID field to the JSP.

Answer 1

the example you suggested is using session to store the value. the @SessionAttribute is to bind an existing model object to the session. Look at the source code the class is annotated with @SessionAttributes("pet").Which means your model attribute named “pet” is getting stored in session.Also look at the code in processSubmit method of EditPetForm class

    @RequestMapping(method = { RequestMethod.PUT, RequestMethod.POST })
    public String processSubmit(@ModelAttribute("pet") Pet pet, BindingResult result, SessionStatus status) {
        new PetValidator().validate(pet, result);
        if (result.hasErrors()) {
            return "pets/form";
        }
        else {
            this.clinic.storePet(pet);
            status.setComplete(); //look at its documentation
            return "redirect:/owners/" + pet.getOwner().getId();
        }
    }

I havnt used something like this before.But i guess putting ur id in session is the way