Compatibility matrix for jdtls milestones?

[ben133290]

Hello, I am new to using jdtls, so maybe this already exists somewhere and I haven't seen it, but is there a compatibility matrix somewhere documented that can tell me which jdtls version requires which minimum java version? I am looking for the latest version that i can use with java version 21 without getting an exit code 13.

[fbricon]

Java 21 has been required to run jdt.ls since version 1.44. What's your issue exactly? how do you run it?

And no there's no compatibility matrix.

[ben133290]

Not really an issue, just trying to find compatability information.

I used mason to install the latest jdtls version for use with neovim but it crashes when i open a java file because it appears to require at least version 25 based on this log output generated by the jdtls --version command.

!SESSION 2025-11-14 09:47:13.694 -----------------------------------------------
eclipse.buildId=unknown
java.version=21.0.9
java.vendor=Oracle Corporation
BootLoader constants: OS=macosx, ARCH=aarch64, WS=cocoa, NL=en_US
Framework arguments:  --version
Command-line arguments:  -data /Users/user/Library/Caches/jdtls/jdtls-e6fb06210fafc02fd7479ddbed2d042cc3a5155e --version

This is a continuation of log file /Users/user/Library/Caches/jdtls/jdtls-e6fb06210fafc02fd7479ddbed2d042cc3a5155e/.metadata/.bak_0.log
Created Time: 2025-11-14 09:47:14.212

!ENTRY org.eclipse.jdt.core.javac 2 0 2025-11-14 09:47:14.212
!MESSAGE Could not resolve module: org.eclipse.jdt.core.javac [52]
  Unresolved requirement: Require-Capability: osgi.ee; filter:="(&(osgi.ee=JavaSE)(version=25))"

Therefore, I am trying to find out which version is the newest jdtls version that still works with java version 21.

[fbricon]

jdt.ls embeds an optional plugin, org.eclipse.jdt.core.javac (allowing you to delegate compilation to javac instead of ECJ) that requires java 25. That plugin fails to start if jdt.ls is launched with Java < 25, but that should not prevent the language server from running normally for anything else. So beside that scary error in the log, does the server actually work or not?

[ben133290]

I see, in that case it likely wasn't a version issue after all. It was not working before, but I tried clearing the workspace cache and it seems to have fixed the error i was getting.
i.e. what did the trick:

rm -rf ~/.cache/jdtls/workspace/*
rm -rf /Users/ben/Library/Caches/jdtls/*

[fbricon]

I just installed nvim / LazyVim on my Mac, and by some miracle I managed to install jdtls with MasonInstall. Running with Java 21, it seems to work for me.