While you could use a filter for server-side anything, including validation, I don't think it's a good idea. Filters are best used for purposes that are orthogonal to the
servlets that will be running. In other words, if the servlets depend upon the filter being run in order to execute properly, such as with the validation idea, then what good is it to take that logic out of the servlet and put it in a filter? There are much better ways to share common code (if that's the idea behind it).
I do not know what a servletlister is.