public static String getKey(String dataId, String group) {
        return getKey(dataId, group, "");
    }
@Test
    public void getKey() {
        String dataId = "dataId";
        String group = "group";
        String datumStr = "datumStr";
        String expected = "dataId+group+datumStr";
        String key = GroupKey.getKey(dataId, group, datumStr);
        Assert.isTrue(key.equals(expected));
    }