@Test
public void testOptionalNull()throws B2JsonException {

    String json =
            "{" +
            "  \"v_string\" : null,\n" +
            "  \"v_empty\" : null\n" +
            "}";
    AllOptionalTypes obj = b2Json.fromJson(json, AllOptionalTypes.class);
    assertNull(obj.v_string);
    assertNull(obj.v_empty);
}