VS Code Language Server Example in Java
The repo contains the end-result of an 'exercise' to implement a simple VS Code Language Server in Java.
The starting point is a clone of this repo:
https://github.com/georgewfraser/vscode-javac
It provides Java support using the javac API.
As such that repo contains all the pieces necessary to create a working Language Server. In this exercise we stripped it down to the bare minimum to make a very basic language server similar to the one built in the VScode tutorial on building a language server.
Running
The extension implemented in this example consists out of two pieces:
- client: a typescript js app that launches and connects to the language server.
- server: server app, implemented in Java.
First build the server:
mvn clean package
The server will be produced in out/fat-jar.jar.
Then build the client:
npm clean install
Now you can open the client-app in vscode. From the root of this project.
code .
To launch the language server in a vscode runtime, press F5.
Debugging
To debug the language server, open lib/Main.ts and edit to set the
DEBUG constant to true. When you laucnh the app next by pressing
F5 it will launch with debug options being passed to the JVM.
You can then connect a 'Remote Java' Eclipse debugger on port 8000.
Note that in debug mode we launch not from the 'fatjar' produced by the maven build, but instead use the classes from 'target/classes' directory. This allows you to edit the server code in Eclipse and relaunch the client from vscode without rebuilding the fatjar.