@Test
public void testJsonEnumMap() throws Exception {

    LOG.info("testJsonEnumMap");
    final Map<MyEnumType, Integer> x = new EnumMap<>(MyEnumType.class);
    x.put(MyEnumType.A, 100);
    x.put(MyEnumType.B, 200);
    x.put(MyEnumType.C, 300);
    x.put(MyEnumType.D, 400);
    final String s = Json.toJson(x);
    LOG.info("x.toJson = {}", s);
    Assert.assertEquals(
            "{\"A\":100,\"B\":200,\"C\":300,\"D\":400}",
            s);
}