Customize JSON serialization with JaxRS

Question

In a webservice call, I would like to return my objects with this JSON structure.

{
  "date" : "30/06/2014",
  "price" : {
    "val" : "12.50",
    "curr" : "EUR"
  }
}

I'd like to map this JSON code to this Java structure (with joda-time and joda-money):

public class MyResponse {
  LocalDate date;
  Money price;
}

My webservice currently looks like this:

@javax.ws.rs.POST
@javax.ws.rs.Path("test")
@javax.ws.rs.Produces({MediaType.APPLICATION_JSON})
@javax.ws.rs.Consumes({MediaType.APPLICATION_JSON})
public MyResponse test(MyRequest request) {
  MyResponse response = new MyResponse();
  response.setDate(LocalDate.now());
  response.setMoney(Money.parse("EUR 12.50"));
  return response;
}

So my question is: where do I register a custom handler to format dates as I want as well as money representations?

Answer 1

If you are using Jackson (which should be the default for JBoss EAP 6) you can use custom JsonSerializers

For the LocalDate:

public class DateSerializer extends JsonSerializer<LocalDate> {

    @Override
    public void serialize(LocalDate date, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        jgen.writeString(date.toString("dd/MM/yyyy"));
    }

}

For the Money:

public class MoneySerializer extends JsonSerializer<Money> {

    @Override
    public void serialize(Money money, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeStringField("val", money.getAmount().toString());
        jgen.writeStringField("curr", money.getCurrencyUnit().getCurrencyCode());
        jgen.writeEndObject();
    }

}

Both Serializers can be registered globally:

@Provider
public class JacksonConfig implements ContextResolver<ObjectMapper> {

    private ObjectMapper objectMapper;

    public JacksonConfig() {
        objectMapper = new ObjectMapper();
        SimpleModule module = new SimpleModule("MyModule", new Version(1, 0, 0, null));
        module.addSerializer(Money.class, new MoneySerializer());
        module.addSerializer(LocalDate.class, new DateSerializer());
        objectMapper.registerModule(module);
    }

    public ObjectMapper getContext(Class<?> objectType) {
        return objectMapper;
    }

}

For parsing JSON in this custom format you need to implement custom JsonDeserializers.

If you are using Jettison you can do the same thing with custom XmlAdapters.