java - Jackson's @JsonView, @JsonFilter and Spring

Question

Can one use the Jackson @JsonView and @JsonFilter annotations to modify the JSON returned by a Spring MVC controller, whilst using MappingJacksonHttpMessageConverterand Spring's @ResponseBody and @RequestBody annotations?

public class Product
{
    private Integer id;
    private Set<ProductDescription> descriptions;
    private BigDecimal price;
    ...
}


public class ProductDescription
{
    private Integer id;
    private Language language;
    private String name;
    private String summary;
    private String lifeStory;
    ...
}

When the client requests a collection of Products, I'd like to return a minimal version of each ProductDescription, perhaps just its ID. Then in a subsequent call the client can use this ID to ask for a full instance of ProductDescription with all properties present.

It would be ideal to be able to specify this on the Spring MVC controller methods, as the method invoked defines the context in which client was requesting the data.

Answer 1

Ultimately, we want to use notation similar to what StaxMan showed for JAX-RS. Unfortunately, Spring doesn't support this out of the box, so we have to do it ourselves.

This is my solution, it's not very pretty, but it does the job.

@JsonView(ViewId.class)
@RequestMapping(value="get", method=RequestMethod.GET) // Spring controller annotation
public Pojo getPojo(@RequestValue Long id)
{
   return new Pojo(id);
}

---

public class JsonViewAwareJsonView extends MappingJacksonJsonView {

    private ObjectMapper objectMapper = new ObjectMapper();

    private boolean prefixJson = false;

    private JsonEncoding encoding = JsonEncoding.UTF8;

    @Override
    public void setPrefixJson(boolean prefixJson) {
        super.setPrefixJson(prefixJson);
        this.prefixJson = prefixJson;
    }

    @Override
    public void setEncoding(JsonEncoding encoding) {
        super.setEncoding(encoding);
        this.encoding = encoding;
    }


    @Override
    public void setObjectMapper(ObjectMapper objectMapper) {
        super.setObjectMapper(objectMapper);
        this.objectMapper = objectMapper;
    }


    @Override
    protected void renderMergedOutputModel(Map<String, Object> model,
            HttpServletRequest request, HttpServletResponse response)
            throws Exception {

        Class<?> jsonView = null;
        if(model.containsKey("json.JsonView")){
            Class<?>[] allJsonViews = (Class<?>[]) model.remove("json.JsonView");
            if(allJsonViews.length == 1)
                jsonView = allJsonViews[0];
        }


        Object value = filterModel(model);
        JsonGenerator generator =
                this.objectMapper.getJsonFactory().createJsonGenerator(response.getOutputStream(), this.encoding);
        if (this.prefixJson) {
            generator.writeRaw("{} && ");
        }
        if(jsonView != null){
            SerializationConfig config = this.objectMapper.getSerializationConfig();
            config = config.withView(jsonView);
            this.objectMapper.writeValue(generator, value, config);
        }
        else
            this.objectMapper.writeValue(generator, value);
    }
}

---

public class JsonViewInterceptor extends HandlerInterceptorAdapter
{

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response,
        Object handler, ModelAndView modelAndView) {
        HandlerMethod handlerMethod = (HandlerMethod) handler;
        JsonView jsonViewAnnotation = handlerMethod.getMethodAnnotation(JsonView.class);
        if(jsonViewAnnotation != null)
            modelAndView.addObject("json.JsonView", jsonViewAnnotation.value());
    }
}

---

In spring-servlet.xml

<bean name="ViewResolver" class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
        <property name="mediaTypes">
            <map>
                <entry key="json" value="application/json" />
            </map>
        </property>
        <property name="defaultContentType" value="application/json" />
        <property name="defaultViews">
            <list>
                <bean class="com.mycompany.myproject.JsonViewAwareJsonView">
                </bean>
            </list>
        </property>
    </bean>

and

<mvc:interceptors>
    <bean class="com.mycompany.myproject.JsonViewInterceptor" />
</mvc:interceptors>