Question

I am implementing a project with play 1.2.4, based on documentation the right way to handle validation is:

public static void signUp() {
    render();
}

public static void doSignUp(@Required @Valid User user) {
    if (validation.hasErrors()) {
        params.flash();
        validation.keep();
        signUp();
    }
    user.create();
    Application.index();
}

But based on samples provided with play, it seems that different approach is used:

public static void signUp() {
    render();
}

public static void doSignUp(@Required @Valid User user) {
    if (validation.hasErrors()) {
        render("@signUp"); 
    }
    user.create();
    Application.index();
}

For this small example the code difference is small, but in more complex examples it’s not so simple.

Pros and cons I see are:
First approach:

• Gives nice URLs to user

• Always redirects after POST, so no confirm problem if user refreshes page

• Only one method is responsible for filling renderArgs before calling
  template

• Compile time verification that signUp method exits if it gets renamed

Second approach:

• Faster, no redirect/round-trip in browser

So what is the best practice? Which approach to use use along the application?

Answer 1

Let me go over your arguments:

First:

Gives nice URLs to user

The URL can always be fine in Play 1.x. You can use the following:

get  /signUp  myController.signUp
post /signUp  myController.doSignUp

So the first argument doesn’t matter.

Second:

Always redirects after POST, so no confirm problem if user refreshes page.

I think if a user makes a mistake and press F5 or refresh with other technique it’s good if he get the same errors again. If the user should get the possibility to get a clean form, I prefer to have a cancel-button.

Third:

Only one method is responsible for filling renderArgs before calling template

Can’t see the problem with render("@signUp");

Fourth:

Compile time verification that signUp method exits if it gets renamed.

Ok, this is an argument but I think it’s weak. Will be false with play 2.0.

So I think both approaches can be good, depending on the situation. Specially if you have a large form, the redirect won’t work. As default I would recommend the second solution.
However, I don’t know how the situation with play 2.0 will be.