@Test
    public void test() {
        String inputString
                = "{\"clazz\":com.foo.MyObject,\"value\":20}";
        IdDeserializer deserializer = new IdDeserializer();
        Gson gson = new GsonBuilder()
                .registerTypeAdapter(Id.class, deserializer)
                .create();
        Id outList = gson.fromJson(inputString, new TypeToken<Id>(){}.getType());
        System.out.println(outList.getValue());
    }

@Test
   public void test() {
       Id id = new Id(Foo.class, 20);
       Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdSerializer()).create();
       Gson gson2 = new GsonBuilder()
               .registerTypeAdapter(Id.class, new IdDeserializer())
               .create();
       Id outList = gson2.fromJson(gson.toJson(id), new TypeToken<Id>(){}.getType());
       System.out.println(outList.getValue());
   }