I have a build that needs to run with jdk6. However, the software being built needs to be run on jdk5. Specifying

sourceCompatibility = 1.5

achieves this (the compiler generates java1.5-compatible class files).

Now I'm running our build on a system where JAVA_HOME and the PATH were set to a jdk1.5. Since I (initially) didn't want to alter the build environment there, I simply added

-Dorg.gradle.java.home=/path/to/jdk6

in the gradle launch.

When doing so, everything seems to work as expected, but all generated class files are java1.6 class files, so it looks like the sourceCompatibility gets ignored in this scenario.

I then created a simple test project to reproduce the problem and added

println "Running on Java: ${System.getProperty('java.version')}"

at the top of the buildfile. Surprisingly, even with the org.gradle.java.home option set to the 1.6 jdk, it still said it was running on the java5 vm.

I had expected gradle to fork a completely new VM before even starting the build, but that's apparently not the case. This behavior might be surprising and even disturbing (imagine if someone does jdk-specific things in the build and gets the wrong jdk version number...)!