无法通过JDBC和JSch连接到MySQL服务器

Question

我试图通过SSH隧道（JSch）连接到我的Linux服务器上的MySQL服务器（JDBC），但我总是得到一个

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.

奇怪的是，当我尝试使用相同设置连接图形客户端（例如Sequel Pro）时，我没有任何问题。这是I级工作的片段，供参考：

private DatabaseManager(Logger logger, Configuration config) {
    this.logger = logger;
    this.marker = MarkerFactory.getMarker(this.getClass().getSimpleName());

    try {
        sshTunnel = config.get(EnvironmentSetting.SSH_TUNNEL, Boolean.TYPE);

        databaseHost = config.get(EnvironmentSetting.DATABASE, String.class);
        databasePort = config.get(EnvironmentSetting.DATABASE_PORT, Integer.TYPE);
        databaseUser = config.get(EnvironmentSetting.DATABASE_USER, String.class);
        databasePassword = config.get(EnvironmentSetting.DATABASE_PASSWORD, String.class);
        database = config.get(EnvironmentSetting.DATABASE, String.class);

        Preconditions.checkNotNull(this, "Basic database configuration must be set", sshTunnel,
                databaseHost, databasePort, databaseUser, databasePassword, database);

        if (sshTunnel) {
            sshHost = config.get(EnvironmentSetting.REMOTE_IP, String.class);
            sshPort = config.get(EnvironmentSetting.REMOTE_PORT, Integer.TYPE);
            sshUser = config.get(EnvironmentSetting.REMOTE_USER, String.class);
            sshKeyPath = config.get(EnvironmentSetting.LOCAL_KEY, String.class);
            sshKeyPassword = config.get(EnvironmentSetting.LOCAL_KEY_PASSWORD, String.class);
            localBindPort = config.get(EnvironmentSetting.LOCAL_PORT, Integer.TYPE);

            Preconditions.checkNotNull(this, "SSH tunnel settings must be set if enabled", sshHost,
                    sshPort, sshUser, sshKeyPath, localBindPort);

            connectSshTunnel();
        }
    } catch (ConfigurationValueNotFoundException e) {
        e.printStackTrace();
        logger.warn(marker, e.getMessage());
        logger.warn(marker, "Unable to use config values");
    }

    MysqlDataSource dataSource = new MysqlDataSource();
    dataSource.setServerName(sshTunnel ? "localhost" : databaseHost);
    dataSource.setPort(sshTunnel ? localBindPort : databasePort);
    dataSource.setDatabaseName(database);
    dataSource.setUser(databaseUser);
    dataSource.setPassword(databasePassword);

    this.dataSource = dataSource;

    // Connection test
    try {
        Connection connection = dataSource.getConnection();

        String catalog = connection.getCatalog();
        logger.info(marker, catalog);
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

private void connectSshTunnel() {
    try {
        final JSch jsch = new JSch();
        session = jsch.getSession(sshUser, sshHost, sshPort);
        jsch.addIdentity(FileUtil.cleanFile(sshKeyPath), !sshKeyPassword.equals("") ? sshKeyPassword
                : null);

        final Properties config = new Properties();
        config.put("StrictHostKeyChecking", "no" );
        session.setConfig(config);

        session.connect();
        logger.info(marker, "Successfully connected SSH tunnel");

        final int assignedPort = session.setPortForwardingL(localBindPort, sshHost, databasePort);
        logger.info(marker, String.format("Port forwarded: localhost:%d -> %s:%d", assignedPort, sshHost, databasePort));
    } catch (JSchException e) {
        e.printStackTrace();
        logger.warn(marker, e.getMessage());
        logger.warn(marker, "Failed to setup JSch");
    }
}