I noticed that when there is no installer available for a JDK, the JAVA_HOME environment variable will be empty in the environment of a build. This will happen for example when there is no installer configured for a JDK. In that case it's not hard to find the cause. But for the case I describe below it's much harder to find out why JAVA_HOME is empty.

Therefore I think logging should be improved when a specific JDK is configured for that build and no installer is available for that JDK. Furthermore JAVA_HOME should be set to match the default JVM.

Here are the steps to reproduce:

• Configure two JDK's, named JDK1 and JDK2 (because if you have only one JDK you can't select one in a job)
• Add an 'Extract .zip/.tar.gz' installer to JDK1 and set the label for this installer to 'jdk1', so it won't be available for installation on nodes to which this label is not assigned
• Create a freestyle job and select JDK1 as JDK
• Run the job and check that JAVA_HOME is empty