Wizard form with Spring MVC

Today I will show you how to create a wizard form with Spring MVC. A wizard form is a multi-step form that allows users to submit information gradually. With Spring MVC it's very easy to make such a form, as well as validate already submitted data on each step and on finish.

Controller

This is the main thing. Let's take a detailed look.

The controller is annotated with the @Controller annotation. @RequestMapping specifies its path. Also, we are storing user submitted data (an instance of my custom transfer object called PersonTo) in session with the @SessionAttributes annotation.

@Controller
@RequestMapping("/personRegistration")
@SessionAttributes("personTo")
public class PersonRegistrationController {

Now, let's take a look at initialisation code. The controller expects an appropriate validator to be passed during construction time. The validator is, in our case, a Spring bean, so we can have it autowired.
Then we initialise an init binder for the custom Gender enum. That allows incoming string parameters to be converted into enum instances.

@Autowired
   public PersonRegistrationController(PersonRegistrationValidator validator) {
       super();
       this.validator = validator;
   }

   @InitBinder
   public void initBinder(WebDataBinder binder) {
       binder.registerCustomEditor(Gender.class, new GenderEditor());
   }

Next, look at the method that handles GET requests. This method resets the potentially submitted data by creating a new PersonTo object and storing it in session. It requests the registration name form to be displayed. (The forms code will soon follow)

   @RequestMapping(method = RequestMethod.GET)
   public String setupForm(Model model) {
       PersonTo personTo = new PersonTo();
       model.addAttribute(PERSON_TO, personTo);
       return REGISTRATION_NAME_FORM;
   }

And now the big thing. The method that handles POST requests which are those where the user actually submitted data.

@RequestMapping(method = RequestMethod.POST)
   public String submitForm(HttpServletRequest request,
           HttpServletResponse response,
           @ModelAttribute(PERSON_TO) PersonTo personTo, BindingResult result,
           SessionStatus status, @RequestParam("_page") int currentPage,
           Model model) {

       Map<Integer, String> pageForms = new HashMap<Integer, String>();
       pageForms.put(0, REGISTRATION_NAME_FORM);
       pageForms.put(1, REGISTRATION_GENDER_FORM);

       if (userClickedCancel(request)) {
           status.setComplete();
           return REDIRECT_TO_HOMEPAGE;
       } else if (userIsFinished(request)) {
           validator.validate(personTo, result);
           if (result.hasErrors()) {
               return pageForms.get(currentPage);
           } else {
               log.info("Registration finished for person [{}: {}].",
                       personTo.getGender(), personTo.getName());
               personTo.setRegistrationComplete(true);
               return REDIRECT_TO_SUCCESS_PAGE;
           }
       } else {
           int targetPage = WebUtils.getTargetPage(request, "_target",
                   currentPage);
           if (userClickedPrevious(currentPage, targetPage)) {
               return pageForms.get(targetPage);
           } else {
               switch (currentPage) {
               case 0:
                   validator.validateName(personTo, result);
                   break;
               }
               case 1:
                   validator.validateGender(personTo, result);
                   break;
               }


               if (result.hasErrors()) {
                   return pageForms.get(currentPage);
               } else {
                   return pageForms.get(targetPage);
               }
           }
       }
   }

1. If the user clicked cancel, cancel the whole thing by ending the session and redirect to the home page.
2. If the user is finished, validate the whole session stored transfer object. Redirect to success page or display errors.
3. Otherwise, this is another step in the wizard. In that case, establish which step it is and apply correct validation. If there are errors, show the current page where Spring will display error messages. If everything is OK, go to the next page.

View

I'm using Velocity. Here's the first form where the user types their name. Look at the Next and Cancel buttons (the names are important, _target1 and _cancel) and at the hidden input with page number (zero, since this is the first page in the wizard).

       <form method="post" modelAttribute="personTo">
           <table>
               <tr>
                   <td>Your name:</td>
                   <td>#springFormInput("personTo.name" "")
                   </td>
                   <td>#springShowErrors("" "")
                   </td>
               </tr>
               <tr>
                   <td colspan="3">
                       <input type="submit" value="Next" name="_target1">
                       <input type="submit" value="Cancel" name="_cancel">
                       <input type="hidden" value="0" name="_page">
                   </td>
               </tr>
           </table>
       </form>

And the gender selection page. Note we are using a drop down list here.

       <form method="post" modelAttribute="personTo">
           <table>
               <tr>
                   <td>Your gender:</td>
                   <td>#springFormSingleSelect("personTo.gender" $genders "")
                   </td>
                   <td>#springShowErrors("" "")
                   </td>
               </tr>
               <tr>
                   <td colspan="3">
                       <input type="submit" value="Previous" name="_target0">
                       <input type="submit" value="Finish" name="_finish">
                       <input type="submit" value="Cancel" name="_cancel">
                       <input type="hidden" value="1" name="_page">
                   </td>
               </tr>
           </table>
       </form>

Property editor

Here's the GenderEditor, if you're interested.

public class GenderEditor extends PropertyEditorSupport {

   @Override
   public String getAsText() {
       if (getValue() == null) {
           return null;
       } else {
           Gender gender = (Gender) getValue();
           return gender.toString();
       }
   }

   @Override
   public void setAsText(String text) throws IllegalArgumentException {
       if (StringUtils.isEmpty(text)) {
           setValue("");
       } else if (text.equalsIgnoreCase("m")) {
           setValue(Gender.MALE);
       } else if (text.equalsIgnoreCase("f")) {
           setValue(Gender.FEMALE);
       } else if (text.equalsIgnoreCase("o")) {
           setValue(Gender.OTHER);
       }
   }
}

We need the getAsText() method for validation purposes. That makes sure that if an unknown value is passed from the view, the resulting value is null (as opposed to the String "null").

Download the source code

The source code for this is available on GitHub.