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

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:
Annotate your bean (eg. #NotEmpty, #Pattern, #Length, #Email etc.)
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";
}
// ....
}
Update your view/jsp to hold error messages:
This article can surely be helpful.

Answer 3

You can change your POST implementation to this:
#RequestMapping(value = "/buy/{buyId}", method = RequestMethod.POST)
public String buyPost(#PathVariable long buyId,
#Valid #ModelAttribute("buyForm") BuyForm buyForm,
BindingResult result) {
buyForm.setId(buyId); // important to do this also in the error case, otherwise,
// if the validation fails multiple times it will not work.
if (result.hasErrors()) {
byForm.setId(buyId);
return "/buy/{buyId}";
}
buyService.buy(buyForm);
return "redirect:/show/{buyId}";
}
Optionally, you can also annotate the method with #PostMapping("/buy/{buyId}") if you use Spring 4.3 or higher.