How to set VM options for JLink launcher executable

Question

When using jlink, a bin/java file is generated. This executable will accept VM options by specifying options on the command line in the usual way (such as -Dsystem.property=value or -Xmx1G).

jlink also provides a --launcher option to create an executable that can be run directly, instead of having to invoke the bin/java executable with a module name.

How do I make the launcher executable pre-configured to use my choice of JVM options?

Answer 1

You can use the add-options jlink plugin.

For example, if you want to set Xmx:

jlink --add-options="-Xmx100m" ...

To see a list of jlink plugins, run jlink --list-plugins.

The add-options plugin is currently documented (JDK14) as follows:

Plugin Name: add-options
Option: --add-options=<options>
Description: Prepend the specified <options> string, which may include
whitespace, before any other options when invoking the virtual machine
in the resulting image.

Beware that some of the plugins are, apparently, unstable (including add-options): https://docs.oracle.com/en/java/javase/12/tools/jlink.html

Answer 2

There are one or two ways of going about this,but mostly I'm going to concentrate on the default java ways.

Actual answer - Use JPackage. JLink is just the image of a runtime. JPackage is your distributable

Support for native packaging formats to give the end user a more natural installation experience. Specifically, the tool will support the following formats:

    Windows: msi, exe
    macOS: pkg, app in a dmg (drag the app into the Applications directory)
    Linux: deb, rpm

The application will be installed in the typical default directory for each platform unless the end-user specifies an alternate directory during the installation process (for example, on Linux the default directory will be /opt).

The ability to specify JDK and application arguments at packaging time that will be used when launching the application

The ability to package applications in ways that integrate into the native platform, for example:

    Setting file associations to allow launching an application when a file with an associated suffix is opened
    Launching from a platform-specific menu group, such as Start menu items on Windows
    Option to specify update rules for installable packages (such as in rpm/deb)

1) - Specify an @Args file

You can make an @args file that you can deploy (bundled) with your jlink app, and reference it when starting the application

java @args -m module/main

2) Use the new environment variable

JDK_JAVA_OPTIONS=--add-opens java.base/java.lang=...... -Xmx1G -Djdk.logging.provider=

https://docs.oracle.com/javase/9/tools/java.htm#JSWOR624

3) Use the JLink/JMod to specify main class in module

https://maven.apache.org/plugins/maven-jmod-plugin/plugin-info.html

      <plugin>
        <artifactId>maven-jmod-plugin</artifactId>
        <version>3.0.0-alpha-1</version>
        <extensions>true</extensions>
        <configuration>
          <module>
          <mainClass>mainClass</mainClass>
        </configuration>
      </plugin>

4) Use JLink to create a custom launcher/Edit JDK_VM_OPTIONS

<plugin>
                        <artifactId>maven-jlink-plugin</artifactId>
                        <version>3.0.0-alpha-2-SNAPSHOT</version>
                        <extensions>true</extensions>
                        <configuration>
                            <noHeaderFiles>true</noHeaderFiles>
                            <noManPages>true</noManPages>
                            <stripDebug>true</stripDebug>
                            <verbose>true</verbose>
                            <compress>2</compress>
                            <launcher>customjrelauncher=module/mainClass</launcher>
                        </configuration>
                        <dependencies>
                            <dependency>
                                <groupId>org.ow2.asm</groupId>
                                <artifactId>asm</artifactId>
                                <version>${maven.asm.version}</version>
                            </dependency>
                        </dependencies>
                    </plugin>

In the generated .sh/.bat there is a variable to specify any custom addon's

You can also specify the main class descriptor in your module-info using moditect if you are using it:

<plugin>
                <groupId>org.moditect</groupId>
                <artifactId>moditect-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <id>add-module-infos</id>
                        <phase>package</phase>
                        <goals>
                            <goal>add-module-info</goal>
                        </goals>
                        <configuration>
                            <overwriteExistingFiles>true</overwriteExistingFiles>
                            <module>
                                <mainClass>mainClassLocation</mainClass>
                            </module>
                        </configuration>
                    </execution>
                </executions>
            </plugin>