Limit modules added by javapackager

Question

I am trying to reduce the size of my application by limiting the modules that it includes. I already did this for my runtime using jlink. However, when I run

Answer 1

Using the command line javapackager, you can make use of the deploy options --limit-modules and --add-modules such as:-

javapackager -deploy 
    --add-modules java.base,java.desktop... 
    --limit-modules java.base,java.desktop,java.naming...
    --module-path your.mods.dir
    -native -outdir OUTPUT_DIR -outfile APPLICATION_NAME 
    -srcdir PACKAGE_SRC_DIR -srcfiles APPLICATION.jar -appclass MAIN_CLASS
    -name "YourApplication" -title "SelfContained"

Or colloquially a deploy ant task would consist of something like:-

<fx:runtime strip-native-commands="false">
    <fx:add-modules value="java.base"/>
    <fx:add-modules value="java.desktop,java.naming..."/>
    <fx:limit-modules value="java.base"/>
    <fx:limit-modules value="java.desktop,java.naming..."/>
    <fx:module-path value="${java.home}/../images/jmods"/>
    <fx:module-path value="${build.dir/modules"/>
</fx:runtime>

Answer 2

So it turns out that the reason why it wasn't honoring my options is because my app jar is not a Java 9 module. It's a plain old jar. In Java 9, javapackager uses jlink to generate the runtime and will not try to limit the number of modules because it can't determine the module dependencies. The -Bruntime option is only for Java Web Start applications. If you want javapackager to not use jlink, you have to use the one in JDK 8.

I cannot turn my app jar into a module due to the complexity involved with all the 3rd party dependencies (you can see the details in this question). And I can't use JDK 8 because I need some APIs added to the Desktop module in Java 9. So, I found a workaround to get a slimmer runtime into the app using the Java 9 javapackager:

1. Generate a slimmer runtime using jlink by specifying only the modules that you need using the --add-modules option. You can use the jdeps command to figure out which modules are needed by all the jars in your app.
2. Generate the .app with the full runtime using javapackger as usual.
3. Open up your generated .app file (macOS) or for Windows, use something that will let you edit the .exe or .msi installer (don't know how to do this myself).
4. On macOS, replace the contents of <myApp>.app/Contents/PlugIns/Java.runtime/Contents/Home with those of your slimmer runtime. Do something similar for the Windows installer.