Connect to remote MySQL database through SSH using Java

My understanding is that you want to access a mysql server running on a remote machine and listening on let's say port 3306 through a SSH tunnel.

To create such a tunnel from port 1234 on your local machine to port 3306 on a remote machine using the command line ssh client, you would type the following command from your local machine:

ssh -L 1234:localhost:3306 mysql.server.remote

To do the same thing from Java, you could use JSch, a Java implementation of SSH2. From its website:

JSch allows you to connect to an sshd server and use port forwarding, X11 forwarding, file transfer, etc., and you can integrate its functionality into your own Java programs. JSch is licensed under BSD style license.

For an example, have a look at PortForwardingL.java. Once the session connected, create your JDBC connection to MySQL using something like jdbc:mysql://localhost:1234/[database] as connection URL.

While the existing answers are correct, they obscure the significant code in bloats of other code.

This is the basic code you need to tunnel your JDBC (or any other) database connection through an SSH channel:

String jumpserverHost = "ssh.example.com";
String jumpserverUsername = "sshuser";
// The hostname/IP address and port, you would use on the SSH server
// to connect to the database.
// If the database runs on the same machine as the SSH server, use "localhost".
String databaseHost = "database.example.com";
int databasePort = 3306;
String databaseUsername = "dbuser";
String databasePassword = "dbpass";

JSch jsch = new JSch();
// Public key authentication example
// (but you can use password authentication, if appropriate).
jsch.addIdentity("~/.ssh/id_rsa");

// Connect to SSH jump server (this does not show an authentication code)
Session session = jsch.getSession(jumpserverUsername, jumpserverHost);
session.connect();

// Forward randomly chosen local port through the SSH channel to database host/port
int forwardedPort = session.setPortForwardingL(0, databaseHost, databasePort);

// Connect to the forwarded port (the local end of the SSH tunnel)
// If you don't use JDBC, but another database client,
// just connect it to the localhost:forwardedPort
String url = "jdbc:mysql://localhost:" + forwardedPort;
Connection con =
    DriverManager.getConnection(url, databaseUsername, databasePassword);

You will also have to deal with host key verification. For that see:
How to resolve Java UnknownHostKey, while using JSch SFTP library?

First of all, thank you works great!

Though, I wonder if I should reuse that Session for every (potentially simultaneous) SQL Connection, or if I should create a new Session every time and only refresh it if for some reason it has expired.

Currently, I would every time I make a connection make a new instance of that Controller here and then do the SQL queries with the connection I got from it, then close it manually.

Would also be nice if I could make the class useable with try-with-resource and it closing itself. Will look into that. Cause I don´t wanna miss closing it.

That´s how the thing looks like, I'm getting DB Connections from right now.

public class ConnectionManager {

private Connection con = null;
private Session session = null;

public Connection getConnection() {
    Connection con = null;

    var settings = new DbSettingsController();

    boolean useSSH = settings.getSetting(SettingKey.UseSSH).equals("true");
    String sshPort = settings.getSetting(SettingKey.SSHPort);
    String sqlIp = settings.getSetting(SettingKey.MySqlIP);
    String sqlPort = settings.getSetting(SettingKey.MySqlPort);

    if(useSSH) {
        JSch jSch = new JSch();
        try {
            this.session = jSch.getSession(settings.getSetting(SettingKey.SSHUser),
                    settings.getSetting(SettingKey.SSHHost),
                    Integer.valueOf(sshPort));
            this.session.setPassword(settings.getSetting(SettingKey.SSHPassword));
            this.session.setConfig("StrictHostKeyChecking", "no");
            this.session.connect();
            this.session.setPortForwardingL(Integer.parseInt(sshPort), sqlIp, Integer.parseInt(sqlPort));
        } catch (JSchException e) {
            e.printStackTrace();
        }
    }

    var connectionString = String.format("jdbc:mysql://%s:%s/%s?autoReconnect=true&useSSL=false",
            sqlIp, useSSH ? sshPort : sqlPort,
            settings.getSetting(SettingKey.MySqlShema));

    var user = settings.getSetting(SettingKey.MySqlUser);
    var password = settings.getSetting(SettingKey.MySqlPassword);

    try {
        con = DriverManager.getConnection(connectionString, user, password);
    } catch (SQLException e) {
        e.printStackTrace();
    }

    return con;
}

public void close() {
    if(this.con != null) {
        try {
            this.con.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    if(this.session != null) {
        this.session.disconnect();
    }
}

If you wonder DbSettingsController I´ve made myself too, just puts settings in a Text column in a local SQLite DB, with a key assigned to it (that enum´s int value). Was just copy paste code I reused from some other project, so it was simple and fast to just do that this way.