Question

I am using the MappingJacksonJsonView in my SpringMVC application to render JSON from my controllers. I want the ObjectId from my object to render as .toString but instead it serializes the ObjectId into its parts. It works just fine in my Velocity/JSP pages:

Velocity:
    $thing.id
Produces:
    4f1d77bb3a13870ff0783c25


Json:
    <script type="text/javascript">
         $.ajax({
             type: 'GET',
             url: '/things/show/4f1d77bb3a13870ff0783c25',
             dataType: 'json',
             success : function(data) {
                alert(data);
             }
         });
    </script>
Produces:
    thing: {id:{time:1327331259000, new:false, machine:974358287, timeSecond:1327331259, inc:-260555739},…}
        id: {time:1327331259000, new:false, machine:974358287, timeSecond:1327331259, inc:-260555739}
            inc: -260555739
            machine: 974358287
            new: false
            time: 1327331259000
            timeSecond: 1327331259
        name: "Stack Overflow"


XML:
    <script type="text/javascript">
         $.ajax({
             type: 'GET',
             url: '/things/show/4f1d77bb3a13870ff0783c25',
             dataType: 'xml',
             success : function(data) {
                alert(data);
             }
         });
    </script>
Produces:
    <com.place.model.Thing>
        <id>
            <__time>1327331259</__time>
            <__machine>974358287</__machine>
            <__inc>-260555739</__inc>
            <__new>false</__new>
        </id>
        <name>Stack Overflow</name>
    </com.place.model.Thing>

Is there a way to stop MappingJacksonJsonView from getting that much information out of the ObjectId? I just want the .toString() method, not all the details.

Thanks.

Adding the Spring config:

@Configuration
@EnableWebMvc
public class MyConfiguration {

    @Bean(name = "viewResolver")
    public ContentNegotiatingViewResolver viewResolver() {
        ContentNegotiatingViewResolver contentNegotiatingViewResolver = new ContentNegotiatingViewResolver();
        contentNegotiatingViewResolver.setOrder(1);
        contentNegotiatingViewResolver.setFavorPathExtension(true);
        contentNegotiatingViewResolver.setFavorParameter(true);
        contentNegotiatingViewResolver.setIgnoreAcceptHeader(false);
        Map<String, String> mediaTypes = new HashMap<String, String>();
        mediaTypes.put("json", "application/x-json");
        mediaTypes.put("json", "text/json");
        mediaTypes.put("json", "text/x-json");
        mediaTypes.put("json", "application/json");
        mediaTypes.put("xml", "text/xml");
        mediaTypes.put("xml", "application/xml");
        contentNegotiatingViewResolver.setMediaTypes(mediaTypes);
        List<View> defaultViews = new ArrayList<View>();
        defaultViews.add(xmlView());
        defaultViews.add(jsonView());
        contentNegotiatingViewResolver.setDefaultViews(defaultViews);
        return contentNegotiatingViewResolver;
    }

    @Bean(name = "xStreamMarshaller")
    public XStreamMarshaller xStreamMarshaller() {
        return new XStreamMarshaller();
    }

    @Bean(name = "xmlView")
    public MarshallingView xmlView() {
        MarshallingView marshallingView = new MarshallingView(xStreamMarshaller());
        marshallingView.setContentType("application/xml");
        return marshallingView;
    }

    @Bean(name = "jsonView")
    public MappingJacksonJsonView jsonView() {
        MappingJacksonJsonView mappingJacksonJsonView = new MappingJacksonJsonView();
        mappingJacksonJsonView.setContentType("application/json");
        return mappingJacksonJsonView;
    }
}

And my controller:

@Controller
@RequestMapping(value = { "/things" })
public class ThingController {

    @Autowired
    private ThingRepository thingRepository;

    @RequestMapping(value = { "/show/{thingId}" }, method = RequestMethod.GET)
    public String show(@PathVariable ObjectId thingId, Model model) {
        model.addAttribute("thing", thingRepository.findOne(thingId));
        return "things/show";
    }
}

Answer 1

Previous answer did the trick, but it was ugly and not well thought out – a clear workaround to actually fixing the problem.

The real issue is that ObjectId deserializes into its component parts. MappingJacksonJsonView sees ObjectId for what it is, an object, and goes to work on it. The deserialized fields being seen in the JSON are the fields that make up an ObjectId. To stop the serialization/deserialization of such an object, you have to configure a CustomObjectMapper that extends ObjectMapper.

Here is the CustomeObjectMapper:

public class CustomObjectMapper extends ObjectMapper {

    public CustomObjectMapper() {
        CustomSerializerFactory sf = new CustomSerializerFactory();
        sf.addSpecificMapping(ObjectId.class, new ObjectIdSerializer());
        this.setSerializerFactory(sf);
    }
}

Here is the ObjectIdSerializer that the CustomObjectMapper uses:

public class ObjectIdSerializer extends SerializerBase<ObjectId> {

    protected ObjectIdSerializer(Class<ObjectId> t) {
        super(t);
    }

    public ObjectIdSerializer() {
        this(ObjectId.class);
    }

    @Override
    public void serialize(ObjectId value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
        jgen.writeString(value.toString());
    }
}

And here is what needs to change in your @Configuration-annotated class:

@Bean(name = "jsonView")
public MappingJacksonJsonView jsonView() {
    final MappingJacksonJsonView mappingJacksonJsonView = new MappingJacksonJsonView();
    mappingJacksonJsonView.setContentType("application/json");
    mappingJacksonJsonView.setObjectMapper(new CustomObjectMapper());
    return mappingJacksonJsonView;
}

You are basically telling Jackson how to serialize/deserialize this particular object. Works like a charm.