AMW application with field validation

Hello. I’m developing an AWM application and I’d like to add field validation. I’ve read the following tutorial (https://www.xwiki.org/xwiki/bin/view/Documentation/DevGuide/Tutorials/Creating%20a%20form%20with%20validation%20and%20tooltips) but I’m having trouble integrating it into my AWM application.
My application has several simple text fields and some selectors (single and multiple). If I edit the class and add a regular expression validation and a message to one of the fields, it’s true that the entry is not saved in the application, but I get a generic error message that has nothing to do with the validation (Server not responding).

Are there any other tutorials besides the one I mentioned that could help me, or could you point me to an intermediate solution that could guide me?

Thank you very much, regards.