I try to write checks for the play-framework and see two different possibilities. I described both and want to know if my understanding is correct (So it\'s more a tutorial
At least your first example appears to be on the correct path. You can compare it to the documentation provided below, but I'd assume from the complexity of your example that you've already referred to it.
http://www.playframework.org/documentation/1.1/validation#custom
I don't know enough about the play framework to comment on the second example.