[java] How do I tell Gradle to use specific JDK version?

I can't figure out to get this working.

Scenario:

• I have an application built with gradle
• The application uses JavaFX

What I want

• Use a variable (defined per developer machine) which points to an installation of a JDK which will be used for building the whole application / tests / ...

I thought about having the gradle.properties file, defining the variable. Something like

JAVA_HOME_FOR_MY_PROJECT=<path to my desired JDK>

What I don't want

• point JAVA_HOME to the desired JDK

I could live with many suggestions:

• a solution that defines a system environment variable which I'm able to check in my build.gradle script
• a variable defined in gradle.properties
• overriding the JAVA_HOME variable only for the build context (something like use JAVA_HOME=<my special JDK path defined somewhere else defined>)
• something else I didn't think about

Question:

• How to wire a variable (how ever defined, as variable in the gradle.properties, system environment variable, ...) to the build process?

I have more than one JDK7 available and need to point to a special version (minimum JDK_u version).

Any answer is appreciated and I'm thankful for every hint to the right direction.