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Build Java Modules into a Native Executable

GraalVM Native Image supports the Java Platform Module System, introduced in Java 9, which means you can convert a modularized Java application into a native executable.

The native-image tool accepts the module-related options such as --module (-m), --module-path (-p), --add-opens, --add-exports (same as for the java launcher). When such a module-related option is used, the native-image tool itself is used as a module too.

In addition to supporting --add-reads and --add-modules, all module related options are considered prior to scanning the module path. This helps prevent class loading errors and allow for better module introspection at runtime.

The command to build a native executable from a Java module is:

native-image [options] --module <module>[/<mainclass>] [options]

Run a Demo

Follow the steps below to build a modular Java application into a native executable. For the demo, you will use a simple HelloWorld Java module gathered with Maven:

├── hello
│   └── Main.java
│       > package hello;
│       > 
│       > public class Main {
│       >     public static void main(String[] args) {
│       >         System.out.println("Hello from Java Module: "
│       >             + Main.class.getModule().getName());
│       >     }
│       > }
│
└── module-info.java
    > module HelloModule {
    >     exports hello;
    > }

Prerequisite

Make sure you have installed a GraalVM JDK. The easiest way to get started is with SDKMAN!. For other installation options, visit the Downloads section.

  1. Download or clone the demos repository and navigate to the directory native-image/build-java-modules/: 
     git clone https://github.com/graalvm/graalvm-demos

     cd graalvm-demos/native-image/build-java-modules
  2. Compile and package the project with Maven: 
     mvn clean package
  3. Test running it on the GraalVM JDK: 
     java --module-path target/HelloModule-1.0-SNAPSHOT.jar --module HelloModule
  4. Now build this module into a native executable: 
     native-image --module-path target/HelloModule-1.0-SNAPSHOT.jar --module HelloModule

    It builds the modular Java application into a native executable called hellomodule in the project root directory that you can run:

     ./hellomodule

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