Runtime JVM options

vmArgs are fixed when the app is packaged. To let users (or yourself) change JVM options afterwards, for example the maximum memory, the app can read them from a file at startup: ${name}.l4j.ini, named after Launch4j, which introduced it.

The options in the file are added after vmArgs. Lines starting with # are comments.

MyApp.l4j.ini

# Additional JVM options
-Xms256m
-Xmx2g
-Dapp.mode=production

tip

Write one option per line: it works with every launcher.

Where the file goes

Platform	Location	Supported by
GNU/Linux	Next to the executable	The startup script
macOS	Contents/Resources	The SCRIPT launcher; the native launchers read the same Info.plist setting
Windows	Next to the EXE	Launch4j (default) and Why; WinRun4J doesn't read it

To ship a default file with the app, add it to additionalResources: it's copied to the right place on each platform.

Maven

<additionalResources>
    <additionalResource>MyApp.l4j.ini</additionalResource>
</additionalResources>

Gradle

javapackager {
    additionalResources = [ file('MyApp.l4j.ini') ]
}

Format details

• GNU/Linux: each line is split on spaces, so several options can share a line, but an option can't contain spaces.
• macOS (SCRIPT launcher): each line is one option, spaces included.
• Windows (Launch4j): options are separated by spaces or new lines, and environment variables like %APPDATA% are expanded.