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Eclipse JDT Language Server

The Eclipse JDT Language Server is a Java language specific implementation of the Language Server Protocol and can be used with any editor that supports the protocol, to offer good support for the Java Language. The server is based on:

Features

Requirements

The language server requires a runtime environment of Java 17 (at a minimum) to run. This should either be set in the JAVA_HOME environment variable, or on the user's path.

Installation

There are several options to install eclipse.jdt.ls:

Some editors or editor extensions bundle eclipse.jdt.ls or contain logic to install it. If that is the case, you only need to install the editor extension. For example for Visual Studio Code you can install the Extension Pack for Java and it will take care of the rest.

Running from the command line

If you built eclipse.jdt.ls from source, cd into ./org.eclipse.jdt.ls.product/target/repository. If you downloaded a milestone or snapshot build, extract the contents.

To start the server in the active terminal, adjust the following command as described further below and run it:

java \
	-Declipse.application=org.eclipse.jdt.ls.core.id1 \
	-Dosgi.bundles.defaultStartLevel=4 \
	-Declipse.product=org.eclipse.jdt.ls.core.product \
	-Dlog.level=ALL \
	-Xmx1G \
	--add-modules=ALL-SYSTEM \
	--add-opens java.base/java.util=ALL-UNNAMED \
	--add-opens java.base/java.lang=ALL-UNNAMED \
	-jar ./plugins/org.eclipse.equinox.launcher_1.5.200.v20180922-1751.jar \
	-configuration ./config_linux \
	-data /path/to/data
  1. Choose a value for -configuration: this is the path to your platform's configuration directory. For Linux, use ./config_linux. For windows, use ./config_win. For mac/OS X, use ./config_mac.
  2. Change the filename of the jar in -jar ./plugins/... to match the version you built or downloaded.
  3. Choose a value for -data: An absolute path to your data directory. eclipse.jdt.ls stores workspace specific information in it. This should be unique per workspace/project.

If you want to debug eclipse.jdt.ls itself, add -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=1044 right after java and ensure nothing else is running on port 1044. If you want to debug from the start of execution, change suspend=n to suspend=y so the JVM will wait for your debugger prior to starting the server.

Running from command line with wrapper script

There is also a Python wrapper script available that makes the start up of eclipse.jdt.ls more convenient (no need to juggle with Java options etc.). A sample usage is described below. The script requires Python 3.9.

./org.eclipse.jdt.ls.product/target/repository/bin/jdtls \
	-configuration ~/.cache/jdtls \
	-data /path/to/data

All shown Java options will be set by the wrapper script. Please, note that the -configuration options points to a user's folder to ensure that the configuration folder in org.eclipse.jdt.ls.product/target/repository/config_* remains untouched.

Development Setup

See Contributing

Managing connection types

The Java Language server supports sockets, named pipes, and standard streams of the server process to communicate with the client. Client can communicate its preferred connection methods by setting up environment variables or alternatively using system properties (e.g. -DCLIENT_PORT=...)

For socket and named pipes, the client is expected to create the connections and wait for the server to connect.

Feedback

Clients

This repository only contains the server implementation. Here are some known clients consuming this server:

Continuous Integration Builds

Our CI server publishes the server binaries to http://download.eclipse.org/jdtls/snapshots/.

P2 repositories are available under http://download.eclipse.org/jdtls/snapshots/repository/.

Milestone builds are available under http://download.eclipse.org/jdtls/milestones/.

License

EPL 2.0, See LICENSE file.