Java is detected via the JAVA_HOME environment variable. If your workspace contains projects that use java, this variable must be set and exported at cmake time.
A successful detection should create output that looks something like this (at cmake time):
-- jni
-- + jni.h found at /usr/lib/jvm/java-1.5.0-sun/include
-- + jni_md.h found at /usr/lib/jvm/java-1.5.0-sun/include/linux
-- + jvm library found at /usr/lib/jvm/java-1.5.0-sun/jre/lib/i386/server/libjvm.so
-- + verify library found at /usr/lib/jvm/java-1.5.0-sun/jre/lib/i386/libverify.so
-- + zip library found at /usr/lib/jvm/java-1.5.0-sun/jre/lib/i386/libzip.so
-- + JAVA_HOME=/usr/lib/jvm/java-1.5.0-sun
An incorrectly or unset environment variable gets you this kind of output:
-- jni
-- - jni.h
-- - jni_md.h
-- - jvm library
-- - verify library
-- - zip library
-- - JAVA_HOME (/path/to/nothing) is either unset or does not point to a valid directory.
-- - This is only an error if some project in your workspace requires java.
And if you indeed have projects that need java, you will later get a proper error (not just a warning) that includes text such as:
CMake Error: The following variables are used in this project, but they
are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the
CMake files:
jni_h_include_dir
used as include directory in directory
/src/V02-02-09/src/c2j-icetray
used as include directory in directory
/src/V02-02-09/src/mmc-icetray
The java tool looks for the files jni.h and others (as listed in the ‘successful detection’ block above.) See the source code in $I3_SRC/cmake/tools/Findjni.cmake for full details.
Warning
If you think you have fixed your environment variables but errors still persist, try removing CMakeCache.txt and rerunning cmake.