The best source of information for a question like this is the
Struts Javadoc. Just look up both the ValidatorForm and the ValidatorActionForm classes and read the overview material. You can find the Struts Javadoc by first going to the
Struts 1 home page and then clicking the Javadoc link in the left navigation bar.
The
Struts Validator Guide is another good source of information. Here's a quote from it:
Once you have configured the Validator Plug-In, so that it can load your Validator Resources you just have to extend org.apache.struts.validator.action.ValidatorForm instead of org.apache.struts.action.ActionForm . Then when the validate method is called, the action's name attribute from the Struts Configuration is used to load the validations for the current form. The form element's name attribute in the Validator configuration should match the action element's name attribute.
An alternative approach is to use the action mapping path attribute. In this case, you extend the ValidatorActionForm instead of the ValidatorForm. The ValidatorActionForm uses the action element's path attribute from the Struts configuration which should match the form element's name attribute in the Validator configuration.
Then a separate action mapping can be defined for each page in a multi-page form, and the validation form can be associated with the action rather than a page number (as shown in the example of a multi-page form in the validator example).