public class Test
{
    final static Logger logger = LoggerFactory.getLogger(Test.class);

    private static String host = "xenia.kubje.org";
    private static int port = 3306;
    private static String user = "jaka";
    private static String password = "...";
    private static String clusterName = "jaka_icluster";

    public static void main( String[] args ) throws Exception
    {
        Map<String, String> commonConfig = new HashMap<String, String>();
        commonConfig.put(PersistenceUnitProperties.LOGGING_LEVEL, "FINER"); // FINEST

        logger.info("Creating cluster EMF...");
        Map<String, String> clusterEmfConfig = new HashMap<String, String>(commonConfig);
        clusterEmfConfig.put(PersistenceUnitProperties.JDBC_DRIVER, "com.mysql.jdbc.Driver");
        clusterEmfConfig.put(PersistenceUnitProperties.JDBC_USER, user);
        clusterEmfConfig.put(PersistenceUnitProperties.JDBC_PASSWORD, password);
        clusterEmfConfig.put(PersistenceUnitProperties.JDBC_URL, "jdbc:mysql://"+host+":"+port+"/"+clusterName+"_global");
        // Note how clusterEmf has the "local variable never read" warning, it's never used.
        EntityManagerFactory clusterEmf = Persistence.createEntityManagerFactory("ClusterPU", clusterEmfConfig);

        logger.info("Creating instance EMF...");
        Map<String, String> instanceEmfConfig = new HashMap<String, String>(commonConfig);
        // Expected: Exception because no driver is set.
        // Actual: works
        EntityManagerFactory instanceEmf = Persistence.createEntityManagerFactory("InstancePU", instanceEmfConfig);

        logger.info("Creating an instance EM...");
        int instanceId = 1;
        Map<String, String> instanceEmConfig = new HashMap<String, String>();
        instanceEmConfig.put(EntityManagerProperties.JDBC_DRIVER, "com.mysql.jdbc.Driver");
        instanceEmConfig.put(EntityManagerProperties.JDBC_USER, user);
        instanceEmConfig.put(EntityManagerProperties.JDBC_PASSWORD, password);
        instanceEmConfig.put(EntityManagerProperties.JDBC_URL, "jdbc:mysql://"+host+":"+port+"/"+clusterName+"_instance_"+instanceId);
        // Expected: a) Exception because no driver was set for EMF or b) use the driver for the EM
        // Actual: Connections using data from clusterEmf are created! (database ..._global)
        EntityManager instanceEm = instanceEmf.createEntityManager(instanceEmConfig);

        logger.info("Loading an entity from the instance EM...");

        Company c = instanceEm.find(Company.class, 66);
        // Exception is thrown here: Table 'jaka_icluster_global.companies' doesn't exist
        System.out.println(c.getName());
    }

}