Create validator using java class

Hi

I have a form and I want to validate a field using a java class.
I have an error executing the process.
Full field and I get the following error:

An Element with id (validator_name) missing from the page template

Help me please

Hi.
Can you post the log you get with this error ?

This error appears when you use a variable in a script and this variable doesn’t exist in your process.