Is it possible to run kotlin grade plugin using jdk 7

Question

My project uses jdk 7 for compatibility reasons.

bottom portion of build.gradle

buildscript {
    ext.kotlin_version = '1.2.0'
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

When I use jdk 7 for gradle, I get this:

java.lang.UnsupportedClassVersionError: org/jetbrains/kotlin/gradle/KotlinGradleModel : Unsupported major.minor version 52.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:270)
    at org.gradle.tooling.internal.provider.serialization.DefaultPayloadClassLoaderRegistry$2.resolveClass(DefaultPayloadClassLoaderRegistry.java:91)
    at org.gradle.tooling.internal.provider.serialization.WellKnownClassLoaderRegistry$2.resolveClass(WellKnownClassLoaderRegistry.java:91)
    at org.gradle.tooling.internal.provider.serialization.PayloadSerializerObjectInputStream.readClass(PayloadSerializerObjectInputStream.java:66)
  ... cut

If I switch to jdk 8 for running grade while project jdk is still jdk7, the build succeed. Is this expected behaviour?

If the plugin was compiled for Java8, then this is expected. (I'm curious - what aspect of your build system *requires* Java7?) — Oliver Charlesworth, Dec 06 '17 at 11:42
But a Java8 JDK ought to be compatible with a Java7 codebase. — Oliver Charlesworth, Dec 06 '17 at 11:47
@OliverCharlesworth should be, but then I wouldn't catch my code calling java 8 libs accidentally. — ThomasEdwin, Dec 06 '17 at 11:49
You can ask Gradle to set the [compilation target to Java 7](https://stackoverflow.com/questions/16654951/gradle-sourcecompatibility-vs-targetcompatibility). — Oliver Charlesworth, Dec 06 '17 at 11:50
`You can ask Gradle to set the compilation target to Java 7` Yes, but it won't make `SecureRandom.getInstanceStrong()` compile error. — ThomasEdwin, Dec 06 '17 at 11:57
In addition to what @OliverCharlesworth suggested: Kotlin compiles the bytecode for the JVM 6 target by default. You can [point the Kotlin compiler to the JDK 7](https://kotlinlang.org/docs/reference/using-gradle.html#attributes-specific-for-jvm) with the `jdkHome` option. — hotkey, Dec 06 '17 at 11:58
`It causes a compilation error for me :/` interesting. I will try it tonight. — ThomasEdwin, Dec 06 '17 at 12:34
I've just tried it myself and it compiles, incorrectly. `SecureRandom.getInstanceStrong()`. I think it was explained by answer https://stackoverflow.com/a/22326989/887290 — ThomasEdwin, Dec 06 '17 at 14:35

score 4 · Accepted Answer · answered Dec 06 '17 at 15:13

After hours of research, I finally found this post:

https://blog.jetbrains.com/kotlin/2017/04/kotlin-1-1-2-is-out/

The Kotlin compiler now requires JDK 8 to run. You shouldn’t notice any changes, because most other Java development tools such as Gradle and the Android toolchain also require JDK 8, so you almost certainly already have it installed. For code generated by the compiler, Java 1.6 compatibility is still the default, and we have no plans to drop support for generating Java 1.6 compatible bytecode.

So, the answer is no.

Is it possible to run kotlin grade plugin using jdk 7

1 Answers1