Besides placeholder substitution what other features should a templating system include?

Just what are the minimum essential features of a templating system besides the obvious placeholder substitution?

Give examples of l开发者_StackOverflowibraries if you wish and what makes them cool and what bits about them suck and maybe should not be there...

• Ability to generate ODT, PDF, RTF, HTML, MS Word, MS Excel, and plain text files from templates
• i18n support
• no need to be a replacement for JSP etc. we have enough of those
• ability to generate source code (Java 5 or more)
• Merge capability
• dynamic loading of templates
• ability to include templates
• 1 single jar with no other dependencies (specially commons-logging)

Here are some of the available templating engines in Java. Velocity, FreeMaker and StringTemplate, I believe are most popular. You can have the best of all of them.