@vscjava/java-language-server

Java Language Server (Eclipse JDT LS wrapper) distributed via npm, designed for integration with GitHub Copilot CLI.

Overview

This package wraps Eclipse JDT Language Server and distributes it via npm following the same platform-specific pattern used by @vscjava/cpp-language-server.

Installation

npm install -g @vscjava/java-language-server

The installation automatically downloads the correct platform configuration for your OS. To bundle a JRE (no separate Java install needed):

npm install -g @vscjava/java-language-server @vscjava/java-ls-jre-win32-x64

Prerequisites

• Node.js >= 16
• Java 21+ (unless using the bundled JRE package)

Usage

Standalone

jdtls --stdio

With Copilot CLI

Add to ~/.copilot/lsp-config.json:

{
  "lspServers": {
    "java": {
      "command": "jdtls",
      "args": ["--stdio"],
      "fileExtensions": {
        ".java": "java"
      }
    }
  }
}

Project Configuration

Create java-lsp.json in your project root:

{
  "repositoryPath": "/path/to/project",
  "java": {
    "home": null,
    "vmargs": ["-Xmx2G"]
  },
  "project": {
    "type": "auto",
    "importOnStartup": true
  }
}

Java Runtime Resolution Order

1. Bundled JRE (optional @vscjava/java-ls-jre-* package)
2. java.home in java-lsp.json
3. JAVA_HOME environment variable
4. java on system PATH

Architecture

@vscjava/java-language-server          (main package - Node.js shell + shared JARs)
├── bin/jdtls.js                       (entry point)
├── lib/install.js                     (platform detection, JVM resolution)
├── lib/detect.js                      (Maven/Gradle project detection)
├── server/plugins/                    (Eclipse JDT LS jars - cross-platform)
└── optionalDependencies:
    ├── @vscjava/java-ls-config-*      (platform-specific launcher config)
    └── @vscjava/java-ls-jre-*         (optional bundled JRE)

Server Files

After installing, place the jdtls server files in server/:

# Download jdtls
curl -L https://download.eclipse.org/jdtls/milestones/1.40.0/jdt-language-server-1.40.0-202410311350.tar.gz | tar xz -C node_modules/@vscjava/java-language-server/server/

License

EPL-2.0 (Eclipse JDT LS), see individual packages for details.