Question

I am trying to implement some flow control in Play 2.0.3, kind of a wizard with several steps. What is the best way to do it in Play?

I want to have multi-step flows, like step1 -> step2 -> finish

The main problem is not to allow user to skip for example step2 and go straight to finish (user can manually input a link in the browser /finish ).

Thanks. Please let me know if I haven’t explained myself well.

Answer 1

A completely stateless way could consist in storing all data in the URLs of steps, where the step n + 1 contains all data from step n:

GET   /step1    controllers.Application.step1
GET   /step2    controllers.Application.step2(dataFromStep1)
GET   /step3    controllers.Application.step3(dataFromStep1, dataFromStep2)
POST  /finish   controllers.Application.finish

The advantages of this solution are its simplicity and the fact that checking that all required steps have been completed before the next step is performed for free by the Play! router.

However, if you have a lot of data your URLs will be huge, making this solution less applicable. In such a case, you need to:

• save data of each step to a persistent storage (using the session is yet another option, but limited in size to 4KB) ;
• identify your users so e.g. the /step2 URL won’t return the same thing for different users ;
• set a timeout to discard an incomplete submission and clean your persistent storage ;
• manually check in your business code that all steps have been completed for the final submission.