According to http://confluence.atlassian.com/display/DOC/Installing+Confluence+Standalone+on+Windows+from+Zip+File#InstallingConfluenceStandaloneonWindowsfromZipFile-2.InstalltheJDK%28JavaDevelopmentKit%29, it is necesasry to install the entire Java Development Kit (JDK).

I question this because the JDK is the JRE plus development tools. Standard practices maximizing security and performance require installing the minimal software necessary to get the job done. The more software installed, the more tools available to malicious users, and the more things to break.

Is it really necessary to install the entire JDK? Why not just the JRE?

I think this is a bug because I cannot think of why the JDK would be required, but I went ahead and filed as an improvement in case I misinterpreted something.