In multi-step forms, only the 'next' button or the 'submit' button on the last step save the current steps form data in the users session. In bigger forms, where the user enters a lot of data on one step, this can be very annoying for the user if he wants to check the previous steps data and loses everything he entered.

To achieve this, we had to extend the SubStepFormEngine, the FormDataBinder and the SubStepFormModel to bind the values to the form step state without validation when the user presses the back button. As you can see in the attached classes, we had to copy a lot of code from the base classes as these could not easily be extended like this. If fixed in the base classes, this could have been done with only a few lines of code in the FormDataBinder (support binding without validation) and in the SubStepFormEngine (calling bindWithoutValidation when the user presses back).