SpringMVC controller: how to stay on page if form validation error occurs

Question

I have next working code in my SpringMVC controller:

@RequestMapping(value = "/register", method = RequestMethod.GET)
public void registerForm(Model model) {
    model.addAttribute("registerInfo", new UserRegistrationForm());
}

@RequestMapping(value = "/reg", method = RequestMethod.POST)
public String create(
        @Valid @ModelAttribute("registerInfo") UserRegistrationForm userRegistrationForm,
        BindingResult result) {

    if (result.hasErrors()) {
        return "register";
    }
    userService.addUser(userRegistrationForm);
    return "redirect:/";
}

In short create method try to validate UserRegistrationForm. If form has errors, it leaves user on the same page with filled form fields where error message will be shown.

Now I need to apply the same behaviour to another page, but here I have a problem:

@RequestMapping(value = "/buy/{buyId}", method = RequestMethod.GET)
public String buyGet(HttpServletRequest request, Model model, @PathVariable long buyId) {
    model.addAttribute("buyForm", new BuyForm());
    return "/buy";
}

@RequestMapping(value = "/buy/{buyId}", method = RequestMethod.POST)
public String buyPost(@PathVariable long buyId,
                          @Valid @ModelAttribute("buyForm") BuyForm buyForm,
                          BindingResult result) {

    if (result.hasErrors()) {
        return "/buy/" + buyId;
    }

    buyForm.setId(buyId);
    buyService.buy(buyForm);
    return "redirect:/show/" + buyId;
}

I faced with issue of dynamic url. Now if form has errors I should specify the same page template to stay on current page, but also I should pass buyId as a path variable. Where are a conflict in this two requirements. If I leave this code as is, I get an error (I'm using Thymeleaf as a template processor):

Error resolving template "/buy/3", template might not exist or might not be accessible by any of the configured Template Resolvers

I can write something like return "redirect:/buy/" + buyId, but in this case I lose all data and errors of form object.

What should I do to implement in buyPost method the same behaviour as in create method?

Answer 1

I tried the solution metioned in this post at this weekend, but it doesn't work for BindingResult.

The code below works but not perfect.

@ModelAttribute("command")
public PlaceOrderCommand command() {
    return new PlaceOrderCommand();
}

@RequestMapping(value = "/placeOrder", method = RequestMethod.GET)
public String placeOrder(
        @ModelAttribute("command") PlaceOrderCommand command,
        ModelMap modelMap) {
    modelMap.put(BindingResult.MODEL_KEY_PREFIX + "command",
            modelMap.get("errors"));
    return "placeOrder";
}

@RequestMapping(value = "/placeOrder", method = RequestMethod.POST)
public String placeOrder(
        @Valid @ModelAttribute("command") PlaceOrderCommand command,
        final BindingResult bindingResult, Model model,
        final RedirectAttributes redirectAttributes) {
    if (bindingResult.hasErrors()) {
        redirectAttributes.addFlashAttribute("errors", bindingResult);

        //it doesn't work when passing this          
        //redirectAttributes.addFlashAttribute(BindingResult.MODEL_KEY_PREFIX + "command", bindingResult);

        redirectAttributes.addFlashAttribute("command", command);
        return "redirect:/booking/placeOrder";
    }
    ......
}

Answer 2

*I'm using Hibernate Validator APIs to validate my beans. To preserve form data along with displaying error messages, you need to do these 3 things:

1. Annotate your bean (eg. @NotEmpty, @Pattern, @Length, @Email etc.)

2. Inside controller:

   @Controller public class RegistrationController {

   @Autowired
   private RegistrationService registrationService;
   
   @RequestMapping(value="register.htm", method=RequestMethod.GET, params="new")
   public String showRegistrationForm(Model model) {
       if (!model.containsAttribute("employee")) {
           model.addAttribute("employee", new Employee());
       }
       return "form/registration";
   }
   
   @RequestMapping(value="register.htm", method=RequestMethod.POST)
   public String register(@Valid @ModelAttribute("employee") Employee employee, BindingResult bindingResult, RedirectAttributes redirectAttributes) {
       if (bindingResult.hasErrors()) {
           redirectAttributes.addFlashAttribute("org.springframework.validation.BindingResult.employee", bindingResult);
           redirectAttributes.addFlashAttribute("employee", employee);
           return "redirect:register.htm?new";
       }
       registrationService.save(employee);
       return "workspace";
   }
   // ....
   

   }

3. Update your view/jsp to hold error messages:

This article can surely be helpful.