How to force Play 2.1 to compile against other Java version

Question

I developed a Play application using Java 1.7. Now I need to compile it against version 1.6 because it will be executed on another host that still uses 1.6 (and I cannot change that)

So I copied the startup script play to play-1.6 and changed it in a way so that it uses JDK version 1.6 (which I have stored in a directory on my computer)

When executing this modified script in any directory I get the desired info line

play! 2.1.0 (using Java 1.6.0_38 and Scala 2.10.0), http://www.playframework.org

When I execute the same script in my project directory I get the line

play! 2.1.0 (using Java 1.7.0_09 and Scala 2.10.0), http://www.playframework.org

Where is this information stored that the project uses version 1.7 and how can I force it to compile against 1.6?

Update 1

Maxime Calmels proposed to perform a clean in order to eventually remove compiled configuration files. Unfortunately this didn't help.

Update 2

When I typed java-home in the play console, I got the message

[info] None

So I created a file build.sbt and added the content

javaHome := Some(file("/usr/java/jdk1.6.0_38"))

When starting up the play console and type java-home now I get the line

[info] Some(/usr/java/jdk1.6.0_38)

But play still compiles against version 1.7, so no luck with that either.

Update 3

I got it working... BUT only by copying Play and my project to the host where the project should be run and compiled it there. Not a very elegant solution and I still wonder how I could do it locally on my machine.

Answer 1

Wherever you installed Play, you should be able to change the "play" script by replacing this like with:

if [ -z "$JAVA_HOME" ]; then
    JAVA="java"
else
    JAVA="$JAVA_HOME/bin/java"
fi

this new line:

JAVA="/TheFullJavaPath/bin/java"

That should do it. Then that script would use that version. I recommend naming it like you have to play-java-1.X or something.