Tapestry 5 comes with a powerful framework for user input validation. To use it, we have to do very little, while Tapestry does a lot for us—applies validators, decorates fields in error, and displays error messages.

We can provide custom error messages and Regexp patterns using message catalogs. Although this wasn't explained in the chapter, you can also change the styles used to display errors by overriding them in your stylesheet.

Tapestry 5 comes with five validators that will cover most needs. You can combine several of them to achieve the desired result.

You can provide custom validation, for example cross-form validation, in the validate event handler.

To validate the fields of BeanEditForm, the @Validate annotation should be used on either the getter or setter method of the validated property in the edited class.