Detect native JAVA_HOME
jkutner opened this issue · comments
When JAVA_HOME is not set, and the java that is on the PATH is in a location such as /usr/bin, it is not possible to easily detect the location of the JAVA_HOME directory.
Different platforms use different locations, such as:
/Library/Java/JavaVirtualMachines/$VERSION/Contents/Homeon Mac/usr/lib/jvmon LinuxC:\Program Files\Javaon Windows
It is unclear if searching these directories is the correct approach. Doing so adds significant time to the start-up of the command.
As an alternative, if java is on the PATH, we could launch an out-of-process JVM.
Another example on linux mint: /usr/lib/jvm/default-java/jre/lib/amd64/jamvm/libjvm.so
It looks like the key on Linux is:
$ readlink -f /usr/bin/java | sed "s:bin/java::"
If I can translate that into Ruby code that would be great.
On Mac, it's:
$ readlink /usr/bin/java
But that only returns the path to some directory with commands. That directory contains a java_home script, which maybe what we need.
On windows, the registry is the place to look:
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment
Example: https://github.com/jruby/jruby-launcher/blob/master/jvmlauncher.cpp#L439-L454
I think I have Mac covered with 96b583b
Covered for Windows: 96f4587
I think Linux is fixed too. need to test.
Tested