Configure Jackson to omit lazy-loading attributes in Spring Boot

If you are using SpringBoot, ideally you should already have Hibernate4Module. Else add this dependency

    <dependency>
        <groupId>com.fasterxml.jackson.datatype</groupId>
        <artifactId>jackson-datatype-hibernate4</artifactId>
        <version>2.5.3</version>
    </dependency>

Next create a class called "HibernateAwareObjectMapper" or whatever you want to name it:

with following contents:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.hibernate4.Hibernate4Module;

    public class HibernateAwareObjectMapper extends ObjectMapper {

        public HibernateAwareObjectMapper() {
            registerModule(new Hibernate4Module());
        }
    }

for different versions of Hibernate, refer to these Hibernate modules:

// for Hibernate 4.x:
mapper.registerModule(new Hibernate4Module());
// or, for Hibernate 5.x
mapper.registerModule(new Hibernate5Module());
// or, for Hibernate 3.6
mapper.registerModule(new Hibernate3Module());

Now you need to register your HibernateAwareObjectMapper through a message Converter. For this create a Config class that extens extends WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter. (If you already have one just follow the next step).

Now register the MessageConverter using HibernateObjectMapper :

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters){
    List<MediaType> supportedMediaTypes=new ArrayList<>();
    supportedMediaTypes.add(MediaType.APPLICATION_JSON);
    supportedMediaTypes.add(MediaType.TEXT_PLAIN);
    MappingJackson2HttpMessageConverter converter=new MappingJackson2HttpMessageConverter();
    converter.setObjectMapper(new HibernateAwareObjectMapper());
    converter.setPrettyPrint(true);
    converter.setSupportedMediaTypes(supportedMediaTypes);
    converters.add(converter);
    super.configureMessageConverters(converters);
}

Viola !!! That should be enough. This is the pure-java (no-xml) way of doing this for a spring boot web app.

Feel free to comment if you want to add to Answer.

For me the easiest way to achieve this was to extend WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter and override extendMessageConverters method. Inside I've searched for the MappingJackson2HttpMessageConverter and just registered Jackson Hibernate module.

@Configuration
@AutoConfigureAfter(DispatcherServletAutoConfiguration.class)
public class CustomWebMvcAutoConfig extends WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter
{
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        for (HttpMessageConverter converter : converters) {
            if (converter instanceof org.springframework.http.converter.json.MappingJackson2HttpMessageConverter) {
                ObjectMapper mapper = ((MappingJackson2HttpMessageConverter) converter).getObjectMapper();
                mapper.registerModule(new Hibernate4Module());
                // replace Hibernate4Module() with the proper class for your hibernate version.
            }
        }
    }
}

This way you won't lose all the default converters configured by Spring.

With recent versions of Spring Boot this is much easier.

Any beans of type com.fasterxml.jackson.databind.Module will be automatically registered with the auto-configured Jackson2ObjectMapperBuilder and applied to any ObjectMapper instances that it creates. This provides a global mechanism for contributing custom modules when you add new features to your application.

74.3 Customize the Jackson ObjectMapper

First ensure you have the required Jackson dependency:

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-hibernate4</artifactId>
</dependency>

You can then just include the module as a @Bean in the application context.

@Bean
public Module hibernate4Module()
{
    return new Hibernate4Module();
}

I user springboot and hibernamte5.0.x. It works!

1. pom.xml

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-hibernate5</artifactId>
    <version>2.8.4</version>
</dependency>

2. Webconfig

@Configuration
public class WebConfig implements WebMvcConfigurer {

    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        for (HttpMessageConverter converter : converters) {
            if (converter instanceof org.springframework.http.converter.json.MappingJackson2HttpMessageConverter) {
                ObjectMapper mapper = ((MappingJackson2HttpMessageConverter) converter).getObjectMapper();
                mapper.registerModule(new Hibernate5Module());
                // replace Hibernate4Module() with the proper class for your hibernate version.
            }
        }
    }
}