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, JavaServer Pages-based,
Easy-ish installation, Page locking to prevent editing conflicts,
Support for Multiple Wikis, etc.

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