Java Language Server for Neovim

A Java Language Server Protocol implementation built on the Java compiler API, optimized for Neovim.

This is a fork and continuation of georgewfraser/java-language-server. I'm deeply grateful for the original author's amazing work and am continuing development with a focus solely on Neovim LSP integration.

Features

• Autocomplete - Symbols, members, imports with auto-completion
• Go-to-definition - Navigate to class definitions in workspace and JARs (including private repositories)
• Hover information - Type information and Javadoc documentation with proper formatting
• Find references - Find all usages of symbols
• Diagnostics - Real-time linting and error reporting
• Signature help - Parameter information for method calls
• Lombok support - Synthetic members from Lombok annotations (@Data, @Getter, @Setter, @Builder, @AllArgsConstructor, @Slf4j, etc.)
• Private repository support - Seamless integration with Maven repositories requiring authentication
• JAR navigation - Go-to-definition works on dependency JARs with source files

Installation

Prerequisites

• Java 20+
• Maven
• npm
• protobuf

Build

./scripts/build.sh

The language server will be built to dist/lang_server_{linux|mac|windows}.sh

Setup with Neovim

Option 1: Using nvim-jls (Recommended)

Install the Neovim client plugin and follow its documentation.

Option 2: Manual setup with lspconfig

Add to your init.lua:

local lspconfig = require('lspconfig')

lspconfig.jls.setup({
    cmd = { '<path-to-jls>/dist/lang_server_linux.sh' }, -- or mac/windows
    root_dir = lspconfig.util.root_pattern('pom.xml', 'build.gradle', '.git'),
})

Configuration

The language server will automatically detect dependencies from:

• Maven (pom.xml)
• Gradle (build.gradle)
• Bazel (BUILD files)

Manual dependency specification

If automatic detection doesn't work, you can specify dependencies in your project root in a .java-language-server.json file:

{
    "externalDependencies": [
        "junit:junit:jar:4.12:test",
        "junit:junit:4.12"
    ]
}

Or specify them directly:

{
    "classPath": [
        "lib/some-dependency.jar"
    ],
    "docPath": [
        "lib/some-dependency-sources.jar"
    ]
}

Enabling private repository support

Ensure your Maven credentials are configured in ~/.m2/settings.xml:

<servers>
    <server>
        <id>my-private-repo</id>
        <username>your-username</username>
        <password>your-password</password>
    </server>
</servers>

Then download source JARs:

mvn dependency:sources

The language server will inherit the environment and use your Maven credentials for private repositories.

Usage

The language server provides autocomplete and other features using:

• .java files in your workspace
• Java platform classes
• External dependencies from Maven, Gradle, Bazel, or manual configuration

Design

The Java language server uses the Java compiler API to implement language features like linting, autocomplete, and smart navigation, and the language server protocol to communicate with text editors like Neovim.

Incremental updates

The Java compiler API provides incremental compilation at the level of files: you can create a long-lived instance of the Java compiler, and as the user edits, you only need to recompile files that have changed. The Java language server optimizes this further by focusing compilation on the region of interest by erasing irrelevant code.

Contributing

Installing

Before installing locally, you need to install prerequisites: maven, protobuf.

You also need to have Java 20+ installed. Point the JAVA_HOME environment variable to it.

Assuming you have these prerequisites, you should be able to install locally using:

./scripts/build.sh

Logs

The Java service process will output a log file to stderr.