Getting JAVA_HOME at runtime

[Jean-Baptiste Quenot]

Hello,

The Java ports infrastructure provides JAVA_HOME on build-time to
port's Makefile.  But is it possible to get this variable from
/usr/local/bin/java at runtime?

How to change the Java version for a port at runtime in the rc
script?  It is possible to set the preferred JDK in
/usr/local/etc/javavms but then JAVA_HOME still needs to be
set manually.

I would like to avoid hard-coding the JAVA_HOME at build time in
the rc scripts.

Any idea?
-- 
     Jean-Baptiste Quenot
aka  John Banana Qwerty
http://caraldi.com/jbq/