StatefulJackson.java

public class TestJackson {

    static class User {
        String name;
        int age;

        public User(String name, int age) {
            this.name = name;
            this.age = age;
        }
    }

    public static class UserSerializer extends StdSerializer<User> {

        public UserSerializer() {
            this(null);
        }

        public UserSerializer(Class<User> t) {
            super(t);
        }

        @Override
        public void serialize(User value, JsonGenerator jgen, SerializerProvider provider) throws IOException {
            jgen.writeStartObject();
            jgen.writeStringField("name", value.name);
            jgen.writeNumberField("age", value.age);
            jgen.writeEndObject();
        }
    }

    static class StatefulJsonGenerator extends JsonGeneratorDelegate {

        public StatefulJsonGenerator(JsonGenerator d) {
            super(d);
        }
    }

    @Test
    public void jackson() throws IOException {

        StringWriter sw = new StringWriter();
        User brad = new User("brad", 50);

        SimpleModule testModule = new SimpleModule("CustomModule", new Version(1, 0, 0, null, "gid", "aid"));
        testModule.addSerializer(new UserSerializer(User.class));

        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.registerModule(testModule);

        JsonFactory jsonFactory = objectMapper.getFactory();
        JsonGenerator writerJsonGenerator = jsonFactory.createGenerator(sw);
        JsonGenerator jsonGenerator = new StatefulJsonGenerator(writerJsonGenerator);

        objectMapper.writeValue(jsonGenerator, brad);

        System.out.println(sw);

    }
}