Add support for devbox (nix)

[mc-xyz]

In a project I'm using devbox to isolate dependencies into dedicated shell environments. I've installed jdk into the shell environment. I've installed the Oracle.oracle-java extension into VSCode installed on my host machine.

If I run VSCode I get the exception:

[2025-08-01T06:40:18.494Z] [INFO]: Launching Oracle Java SE Language Server with /nix/store/sd8ra19lvsi4dsc1qbjyvch7f3jmxkbp-openjdk-8u442-b06/lib/openjdk and userdir /home/someone/.config/Code/User/workspaceStorage/2194d3a202e963cbb738c071b8f5628c/Oracle.oracle-java/userdir
[2025-08-01T06:40:18.506Z] [INFO]: Language Client: Starting
[2025-08-01T06:40:18.507Z] [INFO]: LSP server launching: 22349
[2025-08-01T06:40:18.508Z] [INFO]: LSP server user directory: /home/someone/.config/Code/User/workspaceStorage/2194d3a202e963cbb738c071b8f5628c/Oracle.oracle-java/userdir
Cannot run on older versions of Java than Java 17.
Please install Java 17 or newer or use --jdkhome
switch to point to its installation directory.
[2025-08-01T06:40:18.958Z] [ERROR]: Cannot find org.netbeans.modules.java.lsp.server in the log!
[2025-08-01T06:40:18.958Z] [INFO]: Please refer to troubleshooting section for more info: https://github.com/oracle/javavscode/blob/main/README.md#troubleshooting
[2025-08-01T06:40:18.958Z] [INFO]: Request to kill LSP server.
[2025-08-01T06:40:18.958Z] [INFO]: Killing LSP server 2234

This issue potentially relates to #392 (I wish to have a way setting the jdk path from a specific environment veriable).

[sid-srini]

Hi @mc-xyz. Thanks for using the extension and writing in. Apologies for the delayed response.

As given in the Getting Started section, the extension requires JDK 17 or higher to run, while projects using lower versions of Java, such as JDK 8, require setting the jdk.project.jdkhome to that JDK. This is also described in the Selecting the JDK section.

It seems that your current project, requires using JDK 8. Thus, you can set the jdk.project.jdkhome to the one inside the nix environment, while keeping the jdk.jdkhome set to a modern JDK on your host machine.
Presently however, as in the earlier linked issue you mentioned, this particular setting is not read from an env variable. You may perhaps set up a symlink which can point to the jdk inside the nix environment, to avoid re-writing the settings.

Please let us know if this helps. Thanks.