調整された JSON シリアル化のために Jackson でカスタム シリアライザーを作成して登録するにはどうすればよいですか?

public class ItemSerializer extends JsonSerializer<Item> {

    @Override
    public void serialize(Item value, JsonGenerator jgen,
                          SerializerProvider provider) throws IOException,
                                                             JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeNumberField("id", value.id);
        jgen.writeNumberField("itemNr", value.itemNr);
        jgen.writeNumberField("createdBy", value.createdBy.id);
        jgen.writeEndObject();
    }
}

SimpleModule simpleModule = new SimpleModule("SimpleModule",
                                              new Version(1,0,0,null));
simpleModule.addSerializer(new ItemSerializer());
mapper.registerModule(simpleModule);

public class ItemSerializer extends JsonSerializer<Item> {

    @Override
    public void serialize(Item value, JsonGenerator jgen,
                          SerializerProvider provider) throws IOException,
                                                             JsonProcessingException {
        // ... (Serialization code)
    }

    @Override
    public Class<Item> handledType() {
        return Item.class;
    }
}

StringWriter writer = new StringWriter();

try {
    mapper.writeValue(writer, myItem);
} catch (JsonGenerationException | JsonMappingException | IOException e) {
    e.printStackTrace();
}