From a maintenance perspective, it is disregarded and discouraged to add application-specific business logic in the JSPs themselves.

In the case of JSPWiki, it would make sense, though, to expose some of the servlet logic in the JSPs:

• Not all behaviors are configurable via jspwiki.properties or special pages.
• Lots of users are relatively development-savvy, but they are not necessarily proficient in servlet-specific competences
• Even if they manage to do away with servlet programming, they don't want the hassle of building JSPWiki
  • I always get the binary bundle to install a new version of JSPWiki. Propagating JSP edits is reasonably simple with a text diff tool, but I don't want to have to setup a full blown Java development environment just for maintaining my Wikis.