Eclipse Jdtls Setup

Manual Installation (Fallback)

If auto-download fails (e.g., no internet, firewall restrictions), install manually:

macOS (Homebrew)

brew install jdtls

macOS / Linux (Manual Download)

1. Download the latest milestone from https://download.eclipse.org/jdtls/milestones/
2. Extract to a directory, for example ~/.local/share/jdtls
3. Set environment variable: export JDTLS_HOME=~/.local/share/jdtls
4. Add to your shell profile (~/.bashrc, ~/.zshrc, etc.)

Windows (Manual Download)

1. Download the latest milestone from https://download.eclipse.org/jdtls/milestones/
2. Extract to a directory, for example %LOCALAPPDATA%\jdtls
3. Set environment variable: JDTLS_HOME=%LOCALAPPDATA%\jdtls

Linux (Package Manager)

Some distributions provide JDTLS packages:

• Arch Linux: pacman -S jdtls
• Other distributions: Check your package repository for jdtls or eclipse-jdt-ls

Verifying the Installation

After installation, verify that the plugins/ directory exists inside your JDTLS installation and contains org.eclipse.equinox.launcher_*.jar.

ls $JDTLS_HOME/plugins/org.eclipse.equinox.launcher_*.jar

LSP Configuration for Copilot CLI

This plugin automatically configures JDTLS via the bundled bin/launch-jdtls bash script (macOS/Linux). The script auto-detects your platform and JDTLS location — no Python wrapper needed.

Windows users must override the config in ~/.copilot/lsp-config.json to use the PowerShell launcher:

{
  "lspServers": {
    "eclipse-jdtls": {
      "command": "powershell",
      "args": ["-ExecutionPolicy", "Bypass", "-File", "C:\\Users\\YOU\\.copilot\\state\\installed-plugins\\eclipse-jdtls\\bin\\launch-jdtls.ps1"],
      "fileExtensions": {
        ".java": "java"
      }
    }
  }
}

Troubleshooting

"Java not found"

• Ensure Java 21+ is installed: java -version
• Set JAVA_HOME environment variable to your JDK path

"Eclipse JDTLS not found"

• Set the JDTLS_HOME environment variable to the JDTLS installation directory
• Ensure the directory contains a plugins/ subdirectory with the launcher JAR

"Configuration directory not found"

• Verify that config_linux/, config_mac/, or config_win/ exists in $JDTLS_HOME
• Re-download JDTLS if these directories are missing

No completions or diagnostics

1. Ensure the project root contains pom.xml or build.gradle
2. For Maven projects, run ./mvnw dependency:resolve (or mvn dependency:resolve if no wrapper) to populate the local cache
3. For Gradle projects, run ./gradlew build (or gradle build if no wrapper) once to populate the local cache
4. Check JDTLS logs for errors

Memory issues

• Increase heap size by setting JAVA_OPTS=-Xmx2G before launching
• Large projects may need 2-4 GB of heap space