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javagradlebuild
Ealrann
Ealrann

Reputation: 397

Gradle: Force another Operating System

I use OperatingSystem.current() for my daily work with gradle. Now, I want to assemble my java project for different platforms, so I change manually my build.gradle files to build for a specific OS.

My question: Is there a way to specify the OS to use (returned by OperatingSystem.current()) directly in the gradle command line? If no, what is the best strategy to do cross building ?

Note: I depend on some libraries that use themselves the OperatingSystem.current().

Upvotes: 0

Views: 1451

Answers (1)

Boaz
Boaz

Reputation: 4669

I'm cringing while writing this, it's wrong on so many levels - I suggest you'll avoid forcing Gradle to think it's in a different OS. But assuming you can't avoid it ->

I all depends on the version of Gradle you're using, I'd assume you're using the latest version (in older version that might be simpler)

OperatingSystem.current() works with the "os.name" environment variable which you can override very simply with a -D flag on the Gradle command.

BUT, and this is a big but, Gradle is not the problem here. The underlying JRE being used to execute the build contains OS specific code - see UNIXProcess on UNIX systems. The current implementation of UNIXProcess blocks overriding the "os.name" value as it performs validations on it. It's possible you'de be able to bypass that by creating a class in org.gradle.internal.os package that exposes the package-private OperatingSystem.resetCurrent() method and then force OperatingSystem.current() to re-evaluate, bypassing any real JRE checks.

Something like so:

print OperatingSystem.current()
System.setProperty("os.name", <some other OS>)
OperatingSystemWrapper.resetCurrent()
print OperatingSystem.current()

After some additional conversation over the comments, now I understand that the real requirement here is to take conditional dependency on native libs in a simple way that will allow the OP to remove dependency on OperatingSyste.current()

Taking a sample

apply plugin: "java"

dependencies {
    compile "org.lwjgl:lwjgl:3.2.0"
    compile "org.lwjgl:lwjgl-platform:3.2.0:natives-windows"
    compile "org.lwjgl:lwjgl-platform:3.2.0:natives-linux"
    compile "org.lwjgl:lwjgl-platform:3.2.0:natives-osx"
}

One can add conditional dependency via a "-P" flag (see https://docs.gradle.org/current/userguide/build_environment.html#sec:gradle_properties_and_system_properties)

apply plugin: "java"

dependencies {
    compile "org.lwjgl:lwjgl:3.2.0"
    if (buildos == "windows") {
       compile "org.lwjgl:lwjgl-platform:3.2.0:natives-windows"
    } else if (buildos == "linux") {
       compile "org.lwjgl:lwjgl-platform:3.2.0:natives-linux"
    } else if (buildos == "osx") {
       compile "org.lwjgl:lwjgl-platform:3.2.0:natives-osx"
    }
}



gradle build -Pbuildos=windows

A similar thing can be done with a "-D" flag, but then you need to access it with System.getProperty

One can take it even further by building custom tasks and configurations (inheriting from compile/implementation) for each flavor instead of relying on -P flags

Upvotes: 1

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