Hi!

In NixOS, is there a way to install multiple JDKs next to each other, and have the "default" (providing the java command) selected by programs.java, but still be able to point some programs (like gradle) to another JDK?

I tried setting programs.java.enabled = true (which installs JDK 21) and environment.systemPackages = [jdk22] (to get JDK 22 in addition), but now my java --version reports v22, with apparently no way to make it point to v21.

Thanks!

I found docs that seem promising: https://github.com/openjfx/javafx-gradle-plugin?tab=readme-ov-file#5-using-a-local-javafx-sdk

However I noticed that after nix-collect-garbage nothing in /run/current-system or /nix/store remains of jfx / javafx. Of the openjfx packages only some drv files remain:

❯ ls /nix/store/*openjfx*
   #                                                 name                                                  type      size         modified
   0   /nix/store/0451pbbdphkz64rfz9f7j6vv38ar80rp-openjfx-deps-22.0.1-ga.drv                             file       4.2 KiB   54 years ago
   1   /nix/store/385rb03mfsfsz7536qzy96cvvamwvwgk-openjfx-deps-21.0.3-ga.drv                             file       4.4 KiB   54 years ago
   2   /nix/store/604ghwk9gy9yxz17yrlrm7nr60qv2iwk-openjfx-modular-sdk-22.0.1-ga_fish-completions.drv     file       2.1 KiB   54 years ago
   3   /nix/store/qrm093p68pzdrd8h9jvqzcdpq0zafnwi-openjfx-modular-sdk-21.0.3-ga.drv                      file       5.1 KiB   54 years ago
   4   /nix/store/v2k5drzq7k6m316n7998616fqyricmv1-openjfx-modular-sdk-22.0.1-ga.drv                      file       4.9 KiB   54 years ago
   5   /nix/store/vbdsg55wkkkbi5n1x2f5dq9x287bksfc-openjfx-modular-sdk-21.0.3-ga_fish-completions.drv     file       2.1 KiB   54 years ago

Is this because I have no application installed that uses these packages? So Nix ignores systemPackages and believes the package is not needed?

In reply to @devurandom:matrix.org

Thanks!

I found docs that seem promising: https://github.com/openjfx/javafx-gradle-plugin?tab=readme-ov-file#5-using-a-local-javafx-sdk

However I noticed that after nix-collect-garbage nothing in /run/current-system or /nix/store remains of jfx / javafx. Of the openjfx packages only some drv files remain:

❯ ls /nix/store/*openjfx*
   #                                                 name                                                  type      size         modified
   0   /nix/store/0451pbbdphkz64rfz9f7j6vv38ar80rp-openjfx-deps-22.0.1-ga.drv                             file       4.2 KiB   54 years ago
   1   /nix/store/385rb03mfsfsz7536qzy96cvvamwvwgk-openjfx-deps-21.0.3-ga.drv                             file       4.4 KiB   54 years ago
   2   /nix/store/604ghwk9gy9yxz17yrlrm7nr60qv2iwk-openjfx-modular-sdk-22.0.1-ga_fish-completions.drv     file       2.1 KiB   54 years ago
   3   /nix/store/qrm093p68pzdrd8h9jvqzcdpq0zafnwi-openjfx-modular-sdk-21.0.3-ga.drv                      file       5.1 KiB   54 years ago
   4   /nix/store/v2k5drzq7k6m316n7998616fqyricmv1-openjfx-modular-sdk-22.0.1-ga.drv                      file       4.9 KiB   54 years ago
   5   /nix/store/vbdsg55wkkkbi5n1x2f5dq9x287bksfc-openjfx-modular-sdk-21.0.3-ga_fish-completions.drv     file       2.1 KiB   54 years ago

Is this because I have no application installed that uses these packages? So Nix ignores systemPackages and believes the package is not needed?

In reply to @devurandom:matrix.org
Thanks! Why did that not happen to other packages in systemPackages? Because they install sth into /run/current-system?

Sadly this does not work. The Gradle JavaFX plugin can take the path to the JavaFX SDK, but that SDK contains JARs and shared objects, while javaPackages.openjfx21 (and 22) contains the raw class files in one directory and the shared object in a separate directory (not sure how the classes will later find them). The JavaFX plugin just says Could not find org.openjfx:javafx-base:..

Maybe I have to write a Nix derivation to make this work?

Sadly this does not work. The Gradle JavaFX plugin can take the path to the JavaFX SDK, but that SDK contains JARs and shared objects, while javaPackages.openjfx21 (and 22) contains the raw class files in one directory and the shared object in a separate directory (not sure how the classes will later find them). The JavaFX plugin says Could not find org.openjfx:javafx-base:..

Maybe I have to write a Nix derivation to make this work?

Sadly this does not work. The Gradle JavaFX plugin can take the path to the JavaFX SDK, but that SDK contains JARs and shared objects, while javaPackages.openjfx21 (and 22) contains the raw class files in one directory and the shared object in a separate directory (not sure how the classes will later find them). The JavaFX plugin says Could not find org.openjfx:javafx-base:..

Maybe I have to write a Nix package to make this work?