JSPWiki is a feature-rich and extensible WikiWiki engine built
around the standard J2EE components (Java,servlets,JSP).

It's features include:WikiMarkup/Structured Text,File attachments,
Templates support,Data storage,Security,Easy plugin interface for
writing your own additions,UTF-8 support,JavaServerPages-based,
Easy-ish installation, Page locking to prevent editing conflicts,
Support for Multiple Wikis,etc.

WWW: http://www.jspwiki.org/