Add basic Emacs configuration instructions

[bertulli]

Hi, thanks for your work. i just set up the server in my Emacs and i thought it could have been useful to share the configuration needed

[brown]

Setting eglot-server-programs is no longer needed with newer versions of Emacs. Just make sure that a script named java-language-server is somewhere in your PATH and that the script starts up the language server.

[bertulli]

thanks! do you remember when/in which version of Eglot this was introduced? it was done by setting the default value of the variable eglot-server-programs. i see that in 1.12.29 there was not, and in 1.19 there is

[brown]

Here's one more thing you'll want to do when using Emacs/Eglot with java-language-server.

The language server sends "jar://" URIs to Emacs when the server knows a Java source file is present inside a source jar file. For me this typically happens when I'm editing a Java file and use xref-find-definitions on a class or method whose source exists in a source jar that Maven copied to my machine. In order to make the command work, Emacs needs to extract a file from the jar. To add that capability to Emacs, download the jarchive package and ensure the jarchive-setup function has been called before Eglot has started.