JGit - Java Git Implementation

JGit is a pure Java library implementing the Git version control system. This tile provides comprehensive documentation and code examples for using JGit in Java applications.

Overview

JGit is a full-featured Git implementation in Java, used by tools like EGit (Eclipse Git plugin), Gerrit, and Gitiles. It provides both high-level "porcelain" commands (similar to Git CLI) and low-level APIs for direct repository manipulation.

Key Features:

• Pure Java implementation
• No native dependencies
• Complete Git protocol support (file, HTTP, SSH, Git)
• Memory-efficient repository access
• Extensible API

Installation

Add JGit as a dependency in your project:

Maven

<dependency>
    <groupId>org.eclipse.jgit</groupId>
    <artifactId>org.eclipse.jgit</artifactId>
    <version>7.6.0.202603022253-r</version>
</dependency>

Gradle

implementation 'org.eclipse.jgit:org.eclipse.jgit:7.6.0.202603022253-r'

Quick Start

Opening a Repository

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
import java.io.File;

public class OpenRepositoryExample {
    public static void main(String[] args) throws Exception {
        FileRepositoryBuilder builder = new FileRepositoryBuilder();
        try (Repository repository = builder
                .setGitDir(new File("/path/to/.git"))
                .readEnvironment()
                .findGitDir()
                .build()) {
            System.out.println("Repository opened: " + repository.getDirectory());
        }
    }
}

Table of Contents

1. Repository Basics
2. Porcelain Commands
3. Remote Operations
4. Low-level API
5. Common Patterns

Repository Structure

JGit provides two main API layers:

• Porcelain: High-level commands similar to Git CLI (e.g., git add, git commit, git clone)
• Plumbing: Low-level APIs for direct repository manipulation

Available Snippets (JGit Cookbook)

The JGit Cookbook provides numerous ready-to-run code snippets:

General Repository Handling

• Open an existing repository
• Create a new repository

Porcelain Commands

• Initialize a new repository
• Add files to index
• Commit files
• List commits (log)
• List tags and branches
• Create/delete branches and tags
• Show diffs between commits/branches
• Show repository status
• Create archives
• Blame (line attribution)
• Add/list notes
• Clean untracked files
• Stash operations
• Garbage collection
• Merge changes

Remote Repository Operations

• Clone remote repositories (HTTP, SSH)
• List remote references
• Fetch from remotes (with prune)
• Push to remotes
• Rebase onto upstream
• In-memory repository cloning
• Checkout GitHub pull requests
• Set remote tracking branches

Low-level API

• Get refs from names
• Parse commit, tree, tag objects
• Read blob contents
• Resolve complex references
• Walk commit graphs
• Read file from specific commit
• List configured remotes
• Read user configuration
• Get file attributes
• Check branch tracking status
• Check merge status
• List files in commits/tags
• Walk tree recursively/non-recursively

GitServlet

• Standalone HTTP Git server example

Getting Help

• Official JGit Documentation
• JGit JavaDoc
• JGit Cookbook Repository