How to specify jvm option in java packages

dani0854 · December 21, 2023, 11:35am

So lets say there is an application with wrapper that executes ${jre}/bin/java -jar/cp ...
And I want to run this application specifying some custom jvm option such as -Xmx, which must be specified between java and -jar/-cp. Nearly all the java application are packaged in way, which makes it impossible. Like in example below:

github.com

NixOS/nixpkgs/blob/d02ffbbe834b5599fc5f134e644e49397eb07188/pkgs/tools/text/languagetool/default.nix#L25


      
            runHook preInstall
          
          
  mkdir -p $out/share
            mv -- * $out/share/
          
          
  for lt in languagetool{,-commandline,-server};do
              makeWrapper ${jre}/bin/java $out/bin/$lt \
                --add-flags "-cp $out/share/ -jar $out/share/$lt.jar"
            done
          
          
  makeWrapper ${jre}/bin/java $out/bin/languagetool-http-server \
              --add-flags "-cp $out/share/languagetool-server.jar org.languagetool.server.HTTPServer"
          
          
  runHook postInstall
          '';
          
          
passthru.tests.languagetool = nixosTests.languagetool;
          
          
meta = with lib; {
            homepage = "https://languagetool.org";
            sourceProvenance = with sourceTypes; [ binaryBytecode ];

I thought of two ways, either adding options as package function arguments, or adding JAVA_OPTS to wrapper. Later approach seem more flexible. But I only was able to find 1 package that used this approach.

What is the common approach to deal with setting custom JVM options?

eskytthe · December 21, 2023, 4:27pm

Sorry I am a java noob - but what about setting the custom JVM options in an module for the pkgs - like here in the apache-kafka module? - https://github.com/NixOS/nixpkgs/blob/d02ffbbe834b5599fc5f134e644e49397eb07188/nixos/modules/services/misc/apache-kafka.nix#L133

_Andrew · December 21, 2023, 7:11pm

That’s the first of the two ways already mentioned, right? See also various extraJavaOptions.

For the sake of completeness I think users could also:

Wrap a jre with additional arguments and pass it via override
Inject additional arguments by string manipulation via overrideAttrs

There doesn’t seem to be a clear convention. It would be nice to have something as ubiquitous as gappsWrapperArgs.

dani0854 · December 21, 2023, 9:18pm

I could do that, but than I would have to replicate all the options passed in the wrapper. Also, if it’s a CLI app, I would have to make a custom wrapper and make it available in Path. I mean it’s a solution, but I am wondering if there is any cleaner way to this.