How to share one jre in a system with many sub modules? #483

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1. meeterp

   added

   enhancementNew feature or requestNew feature or request

   on Oct 23, 2025
2. fvarrui commented on Oct 4, 2026

   

   fvarrui

   on Oct 4, 2026

   Collaborator

   More actions

   Thanks for the request! With Launch4j (the default exeCreationTool) this isn't possible today: JavaPackager builds the Launch4j config itself and the JRE path is either the bundled one or %JAVA_HOME%;%PATH%.

   It is possible with the Why launcher, overriding its config template. I've just tested this on Windows with 2.0.0-rc1:

   1. In each module, set exeCreationTool to why and bundleJre to false:

      <bundleJre>false</bundleJre>
      <winConfig>
          <exeCreationTool>why</exeCreationTool>
      </winConfig>

   2. Add assets/windows/why-ini.vtl to each module (or to your assetsDir), pointing jvm_install to the shared JRE, relative to the EXE's folder:

      mainclass=$info.mainClass
      #set($classpath = $info.jarFile.name)
      #foreach ($cp in $info.classpaths)
      #set($classpath = $classpath + ";" + $cp)
      #end
      classpath=${classpath}
      jvm_install=../jre
      allow_system_java=false
      allow_java_location_lookup=false
      check_main_class=false
      launch_options=${info.name}.l4j.ini
      

      Use forward slashes (../jre): with ..\jre Why finds the JVM but fails to start it.

   3. Put the shared JRE in jre, next to the modules' folders. You can create it with jlink, or package one module with bundleJre=true and customizedJre=false and move its jre folder.

   Keep in mind the installers won't include the shared JRE, as it's outside each app's folder, so you'd need to ship it yourself.

   I'll keep this open as an enhancement: an option to point the EXE to an external JRE that works with the three Windows launchers. Would that cover your case? Do you use the installers or just the app folders?
3. fvarrui

   added

   feedbackWaiting for feedbackWaiting for feedback

   on Oct 4, 2026
4. fvarrui

   added a commit that references this issue on Oct 4, 2026

   Record #483 answer

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