JGit is a lightweight, pure Java library implementing the Git version control system. You can do a lot of operations using Java language such as create or clone Git repos, create branches, make commits, rebase or tag, you can see

this repo to learn how to use JGit and how to code the different commands.

But one thing that does not cover extensively is the authentication process. In this post I am going to show you how how to authenticate to a Git repository with
JGit.

First thing to do is add JGit as dependency:

dependency>
 <groupId>org.eclipse.jgit</groupId>
 <artifactId>org.eclipse.jgit</artifactId>
 <version>4.5.0.201609210915-r</version>
</dependency>
<dependency>
 <groupId>org.slf4j</groupId>
 <artifactId>slf4j-api</artifactId>
 <version>1.7.21</version>
</dependency>

Then let’s see a simple clone without authentication:

@Test
public void should_connect_to_public_repo() throws IOException, GitAPIException {
 final String REMOTE_URL = "https://github.com/lordofthejars/wildfly-example.git";

 // prepare a new folder for the cloned repository
 File localPath = File.createTempFile("TestGitRepository", "");
 localPath.delete();

 // then clone
 try (Git result = Git.cloneRepository()
 .setURI(REMOTE_URL)
 .setDirectory(localPath)
 .call()) {
 // Important to close the repo after being used
 System.out.println("Having repository: " + result.getRepository().getDirectory());
 }
}

In this case no authentication method is set. Now let’s see how to add a username and password in case of for example private repos:

@Test
public void should_connect_using_user_pass() throws IOException, GitAPIException {
 final String REMOTE_URL = "https://asotobu@bitbucket.org/asotobu/backup.git";

 // prepare a new folder for the cloned repository
 File localPath = File.createTempFile("TestGitRepository", "");
 localPath.delete();

 // then clone
 try (Git result = Git.cloneRepository()
 .setURI(REMOTE_URL)
 .setCredentialsProvider(new UsernamePasswordCredentialsProvider("username", "password"))
 .setDirectory(localPath)
 .call()) {
 
 System.out.println("Having repository: " + result.getRepository().getDirectory());
 }
}

In this case you only need to set as credential provider theUsernameAndPasswordCredentialsProvider and pass the required username and password.

The final scenario I am going to show here is how to authenticate against a git repository using your ssh keys, that is using (~/.ssh/id_rsa) and setting the passphrase to access it.

@Test
public void should_connect_to_public_ssh() throws IOException, GitAPIException {
 final String REMOTE_URL = "git@github.com:lordofthejars/wildfly-example.git";

 SshSessionFactory sshSessionFactory = new JschConfigSessionFactory() {
 @Override
 protected void configure(OpenSshConfig.Host host, Session session ) {
 session.setUserInfo(new UserInfo() {
 @Override
 public String getPassphrase() {
 return "passphrase";
 }

 @Override
 public String getPassword() {return null;}

 @Override
 public boolean promptPassword(String message) {return false;}

 @Override
 public boolean promptPassphrase(String message) {return true;}

 @Override
 public boolean promptYesNo(String message) {return false;}

 @Override
 public void showMessage(String message) {}
 });
 }
 };

 File localPath = File.createTempFile("TestGitRepository", "");
 localPath.delete();

 try (Git result = Git.cloneRepository()
 .setURI(REMOTE_URL)
 .setTransportConfigCallback(transport -> {
 SshTransport sshTransport = ( SshTransport )transport;
 sshTransport.setSshSessionFactory( sshSessionFactory );
 })
 .setDirectory(localPath)
 .call()) {
 System.out.println("Having repository: " + result.getRepository().getDirectory());
 }

}

In this case you need to extend JSchConfigSessionFactory to be able to set passphrase to access to private key. To do it you set a custom UserInfoimplementation where the getPassphrase method returns the passphrase to use andpromptPassphrase method should return true.

After that you only need to set the transport configuration to the one created.

We keep learning,
Alex.

Chan eil inneal-ciùil a ghleusar, ‘Dhùisgeas smuain mo chléibh gu aoibh, Mar nì duan o bheul nan caileag, Oidhche mhath leibh, beannachd leibh (Oidche Mhath Leibh – Ossian)

Music: https://www.youtube.com/watch?v=mi4SCOYAdEk