MinimWatch 2.0.12 for Mac gives JavaHomeError

[simoncn]

OK, here is the full story...

It is all about the install location and your educated guess about JRE vs JDK was correct.

The install location for Java on Mac (JDK and JRE) has changed a few times over the last few releases of Java. This makes it slightly tricky for MinimServer to find a suitable Java installation to use. The scheme used by MinimServer 0.8 doesn't work for Java 11 and later, so a change was needed.

The install location for Java depends on the Java version and on whether the JDK or JRE is installed. You can have multiple versions of the JDK installed at the same time. The /usr/libexec/java_home command gives the location of the latest version installed but (it turns out) it only does this for JDK installs, not for JRE installs. I didn't realise this because I always run with the JDK installed. Because of this, MinimServer 2.0.12 is not finding the JRE installation if there is one.

The JRE uses a different install location which (apparently) is hard-wired, so you can only have one version of the JRE installed. The JRE versions that MinimServer 2 supports are JRE 8, JRE 9 and JRE 10. (JRE 10 was the last version of the JRE.) The JDK versions that MinimServer 2 supports are JDK 8, JDK 9, JDK 10, JDK 11, JDK 12, JDK 13 and JDK 14.

It is possible to have both the JDK and JRE installed. It seems reasonable that MinimServer should check for both the JDK and JRE and compare versions, using the latest version of whichever of the JRE or JDK is available. If both are available and the versions are the same, it doesn't matter too much but we need to choose one and my tie-break vote goes to the JDK.

I am hoping that a new version of MinimServer 2 that does this will be available soon. I have written the code and I will test it with various combinations tomorrow.