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I have a little Java program. I build a binary using Graal's native-image (i.e. GraalVM AOT aka SubstrateVM).
My program can be executed either with a Java runtime or from the native-image binary. What's the best way to tell which context I'm running in?
(This might be a bad practice in general but I believe it's inevitable/necessary in certain not-uncommon circumstances.)
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GraalVM is a tool for developers to write and execute Java code. Specifically, GraalVM is a Java Virtual Machine (JVM) and Java Development Kit (JDK) created by Oracle. It is a high-performance runtime that provides improvements in application performance and efficiency.
GraalVM is a Java VM and JDK based on HotSpot/OpenJDK, implemented in Java. It supports additional programming languages and execution modes, like ahead-of-time compilation of Java applications for fast startup and low memory footprint. The first production-ready version, GraalVM 19.0, was released in May 2019.
Run Java FasterGraalVM can run in the context of OpenJDK to make Java applications run faster with a new just-in-time compilation technology. GraalVM takes over the compilation of Java bytecode to machine code.
Edit: There is now an API for that. See user7983712's answer.
The way it's done in the GraalVM is by capturing the com.oracle.graalvm.isaot system property: it is set to true while building AOT images. If you combine that with the fact that static initializers run during image generation, you can use
static final boolean IS_AOT = Boolean.getBoolean("com.oracle.graalvm.isaot")
This boolean will remain true when running the native image.
This is also useful to cut-off paths that you don't want in the final output: for example if you have some code that uses a feature that SVM doesn't support (e.g., dynamic class-loading) you can predicate it with !IS_AOT.
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