The validate () method doesnt exist in servlet API rather these methods are from 3rd party like in
struts where we can use the validate framaework and can the files which you have mentioned .
In validator-rules .xml we define the validation condition of the fields of our form and call then call
validate method to validate form in struts validator_rules.xml in our action class. We need to give path of all these configuration files in our web.xml file.
See some example of struts validator and runt that example and you will be able to understand well.