Using jdk8 and jdk10 in one build

Help/Discuss
1

I’m trying build multiple projects with jdk8 and jdk10. Some projects has common code with android application so most of projects should be build with jdk8. I tried build one application with jdk10, but it is failing.
I tried use solutions like:

  • Setting org.gradle.java.home=/usr/lib/jvm/java-10-oracle in gradle.properties in subfolder.
  • options.forkOptions.executable = project.property(‘javacPath’)
    I got error:
    Could not target platform: ‘Java SE 10’ using tool chain: ‘JDK 8 (1.8)’.
  • I tried use options.bootClasspath, but it is deprecated and JDK10 doesn’t support bootClasspath

My project structure looks like:
build.gradle
settings.gradle
common-component(jdk8)/build.gradle
PC(jdk 10)/build.gradle
PC(jdk 10)/build.properties
device-Android(jdk 8)/build.gradle

I use:
Gradle 4.7
Groovy: 2.4.12
Ant: Apache Ant™ version 1.9.9 compiled on February 2 2017
JVM: 1.8.0_171 (Oracle Corporation 25.171-b11)
OS: Linux 4.13.0-41-generic amd64

2

I tried this a couple of times over the years but always ran into a problem I couldn’t solve (slow build, didn’t work on CI, some task didn’t support configuring a JDK, etc.). My conclusion was that it’s not practical to use a JDK other than the one used to run Gradle. Happy to be proven wrong.

3

I found workaround using this issue from gradle github. Support forked compilation with Java 9 · Issue #3035 · gradle/gradle · GitHub
I know it won’t work for every project with every JVM language, but in my case I use only java in my project so it is not huge problem. Additionally I will keep this solution until android will fully support Java 10 or next LTS release of java.

PC(jdk 10)/build.gradle:

project (‘:pc-client’) {
dependencies {
compile project(‘:net-default’)
testcompile JUNIT
}
compileJava {
options.fork = true
options.forkOptions.javaHome = file(‘/usr/lib/jvm/java-10-oracle’)
targetCompatibility = 1.10
sourceCompatibility = 1.10
}

compileTestJava {
options.fork = true
options.forkOptions.javaHome = file(‘/usr/lib/jvm/java-10-oracle’)
targetCompatibility = 1.10
sourceCompatibility = 1.10
}
}