Avoid Jackson Serialization on Non Fetched Lazy Objects

Avoid Jackson serialization on non fetched lazy objects

I finally found the solution! thanks to indybee for giving me a clue.

The tutorial Spring 3.1, Hibernate 4 and Jackson-Module-Hibernate have a good solution for Spring 3.1 and earlier versions. But since version 3.1.2 Spring have his own MappingJackson2HttpMessageConverter with almost the same functionality as the one in the tutorial, so we don't need to create this custom HTTPMessageConverter.

With javaconfig we don't need to create a HibernateAwareObjectMapper too, we just need to add the Hibernate4Module to the default MappingJackson2HttpMessageConverter that Spring already have and add it to the HttpMessageConverters of the application, so we need to:

1. Extend our spring config class from WebMvcConfigurerAdapter and override the method configureMessageConverters.

2. On that method add the MappingJackson2HttpMessageConverter with the Hibernate4Module registered in a previus method.

Our config class should look like this:

@Configuration
@EnableWebMvc
public class MyConfigClass extends WebMvcConfigurerAdapter{

    //More configuration....

    /* Here we register the Hibernate4Module into an ObjectMapper, then set this custom-configured ObjectMapper
     * to the MessageConverter and return it to be added to the HttpMessageConverters of our application*/
    public MappingJackson2HttpMessageConverter jacksonMessageConverter(){
        MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();

        ObjectMapper mapper = new ObjectMapper();
        //Registering Hibernate4Module to support lazy objects
        mapper.registerModule(new Hibernate4Module());

        messageConverter.setObjectMapper(mapper);
        return messageConverter;

    }

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        //Here we add our custom-configured HttpMessageConverter
        converters.add(jacksonMessageConverter());
        super.configureMessageConverters(converters);
    }

    //More configuration....
}

If you have an xml configuration, you don't need to create your own MappingJackson2HttpMessageConverter either, but you do need to create the personalized mapper that appears in the tutorial (HibernateAwareObjectMapper), so your xml config should look like this:

<mvc:message-converters>
    <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
        <property name="objectMapper">
            <bean class="com.pastelstudios.json.HibernateAwareObjectMapper" />
        </property>
    </bean>
</mvc:message-converters>

Hope this answer be understandable and helps someone find the solution for this problem, any questions feel free to ask!

jackson - do not serialize lazy objects

You can do this with the Jackson @JsonInclude annotation.

According to the latest version's javadoc (2.4 right now) you can specify with a simple annotation if to include or not the annotated property if the field value is null or empty.

By default, it's JsonInclude.Include.ALWAYS, and this means that even if your lazily not-loaded values are null, Jackson does include the property.

Specifying to don't include empty or null values can significantly reduce the size of the JSON response, with all the benefits included..

If you want to change this behavior, you can add the annotation at class-level or single property/getterMethod level.

Try to add the following annotations to the fields you don't want to include if empty:

@JsonInclude(JsonInclude.Include.NON_EMPTY)
@OneToMany(fetch = FetchType.LAZY, mappedBy = ("movie"),cascade = CascadeType.ALL)
private List<Genre> genre;

Jackson doesn't serialize hibernate lazy fetched field

You mixed up @JsonBackReference and @JsonManagedReference, a field marked with @JsonBackReference will not be serialized, it should be on PhysicianNote#physician and @JsonManagedReference should be on notes.

---

Related Topics