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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 arguments like --module (-m), --module-path (-p), --add-opens, --add-exports (same as for the java launcher). When such a module-related argument 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 run time.

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 practice building 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;
    > }

  1. 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.

  2. Download or clone the demos repository and navigate to the directory native-hello-module: 
     git clone https://github.com/graalvm/graalvm-demos
 cd graalvm-demos/native-hello-module
  3. Compile and package the project with Maven: 
     mvn package
  4. Test running it on GraalVM’s JDK: 
     $JAVA_HOME/bin/java --module-path target/HelloModule-1.0-SNAPSHOT.jar --module HelloModule
  5. Now build this module into a native executable: 
     $JAVA_HOME/bin/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 execute:

     ./hellomodule

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