Provide compatible JDK for JDTLS if none installed

[MaddyGuthridge]

What happened?

My workplace requires me to use Java 17, whereas Jdtls requires Java 21. When I use the Redhat Java extension for VS Code, Jdtls appears to run without issue, presumably by downloading a compatible Java runtime.

What did you expect to happen?

Zed's Java extension also downloads a compatible Java runtime for Jdtls.

I was able to work around this by configuring Jdtls to manually point it to a newer install, but it would be lovely it Zed was able to do this automatically.

  "lsp": {
    "jdtls": {
      "initialization_options": {
        "settings": {
          "java": {
            "home": "/home/maddy/.local/share/mise/installs/java/21.0.2"
          }
        }
      }
    }
  }

Environment

Zed: 0.210.4
Platform: Fedora 42
Java: 17 (installed with Mise)

[playdohface]

This is another case of #99 .
Our documentation regarding that is currently subpar and we will work on it. The correct configuration should look like this:

"lsp" : { 
"jdtls": {
      "settings": {
        "java": {
          "home": "/full/path/to/JDK21+",
            }
        }
    }
}

[MaddyGuthridge]

Yep, thanks for the working config. Not quite what I am asking for here though. As per my original issue, VS Code's Java support automatically sets up JDTLS with a working Java version, even if one isn't currently installed. I think it would be helpful if Zed's extension did the same.

My main reasoning for wanting to reduce the configuration barrier as much as possible is because I am currently evalulating Zed as a candidate to replace VS Code as the recommended editor for students at my university. Currently, the process of needing to install two side-by-side Java runtimes to get Java to work nicely in Zed is fine for me, but is far beyond the capabilities of some first-year students who take the course that I teach.

[playdohface]

Ohh I see! That's an interesting proposition, I don't see why it would not be possible to even provide a JDK if we can't find a compatible one installed.