[java] How to customise the Jackson JSON mapper implicitly used by Spring Boot?

I'm using Spring Boot (1.2.1), in a similar fashion as in their Building a RESTful Web Service tutorial:

@RestController
public class EventController {
   @RequestMapping("/events/all")
   EventList events() {
       return proxyService.getAllEvents();
   }
}

So above, Spring MVC implicitly uses Jackson for serialising my EventList object into JSON.

But I want to do some simple customisations to the JSON format, such as:

setSerializationInclusion(JsonInclude.Include.NON_NULL)

Question is, what is the simplest way to customise the implicit JSON mapper?

I tried the approach in this blog post, creating a CustomObjectMapper and so on, but the step 3, "Register classes in the Spring context", fails:

org.springframework.beans.factory.BeanCreationException: 
  Error creating bean with name 'jacksonFix': Injection of autowired dependencies failed; 
  nested exception is org.springframework.beans.factory.BeanCreationException: 
  Could not autowire method: public void com.acme.project.JacksonFix.setAnnotationMethodHandlerAdapter(org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter); 
  nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: 
  No qualifying bean of type [org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter]   
  found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}

It looks like those instructions are for older versions of Spring MVC, while I'm looking for a simple way to get this working with latest Spring Boot.

You can add a following method inside your bootstrap class which is annotated with @SpringBootApplication

    @Bean
    @Primary
    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
    ObjectMapper objectMapper = builder.createXmlMapper(false).build();
    objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
    objectMapper.configure(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS, false);

    objectMapper.registerModule(new JodaModule());

    return objectMapper;
}

When I tried to make ObjectMapper primary in spring boot 2.0.6 I got errors So I modified the one that spring boot created for me

Also see https://stackoverflow.com/a/48519868/255139

@Lazy
@Autowired
ObjectMapper mapper;

@PostConstruct
public ObjectMapper configureMapper() {
    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);

    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);

    mapper.configure(MapperFeature.ALLOW_COERCION_OF_SCALARS, true);
    mapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true);

    SimpleModule module = new SimpleModule();
    module.addDeserializer(LocalDate.class, new LocalDateDeserializer());
    module.addSerializer(LocalDate.class, new LocalDateSerializer());
    mapper.registerModule(module);

    return mapper;
}

I found the solution described above with :

spring.jackson.serialization-inclusion=non_null

To only work starting at the 1.4.0.RELEASE version of spring boot. In all other cases the config is ignored.

I verified this by experimenting with a modification of the spring boot sample "spring-boot-sample-jersey"

The documentation states several ways to do this.

If you want to replace the default ObjectMapper completely, define a @Bean of that type and mark it as @Primary.

Defining a @Bean of type Jackson2ObjectMapperBuilder will allow you to customize both default ObjectMapper and XmlMapper (used in MappingJackson2HttpMessageConverter and MappingJackson2XmlHttpMessageConverter respectively).

I know the question asking for Spring boot, but I believe lot of people looking for how to do this in non Spring boot, like me searching almost whole day.

Above Spring 4, there is no need to configure MappingJacksonHttpMessageConverter if you only intend to configure ObjectMapper.

You just need to do:

public class MyObjectMapper extends ObjectMapper {

    private static final long serialVersionUID = 4219938065516862637L;

    public MyObjectMapper() {
        super();
        enable(SerializationFeature.INDENT_OUTPUT);
    }       
}

And in your Spring configuration, create this bean:

@Bean 
public MyObjectMapper myObjectMapper() {        
    return new MyObjectMapper();
}

spring.jackson.serialization-inclusion=non_null used to work for us

But when we upgraded spring boot version to 1.4.2.RELEASE or higher, it stopped working.

Now, another property spring.jackson.default-property-inclusion=non_null is doing the magic.

in fact, serialization-inclusion is deprecated. This is what my intellij throws at me.

Deprecated: ObjectMapper.setSerializationInclusion was deprecated in Jackson 2.7

So, start using spring.jackson.default-property-inclusion=non_null instead

I am answering bit late to this question, but someone, in future, might find this useful. The below approach, besides lots of other approaches, works best, and I personally think would better suit a web application.

@Configuration
@EnableWebMvc
public class WebConfiguration extends WebMvcConfigurerAdapter {

 ... other configurations

@Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
        builder.serializationInclusion(JsonInclude.Include.NON_NULL);
        builder.propertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
        builder.serializationInclusion(Include.NON_EMPTY);
        builder.indentOutput(true).dateFormat(new SimpleDateFormat("yyyy-MM-dd"));
        converters.add(new MappingJackson2HttpMessageConverter(builder.build()));
        converters.add(new MappingJackson2XmlHttpMessageConverter(builder.createXmlMapper(true).build()));
    }
}

A lot of things can configured in applicationproperties. Unfortunately this feature only in Version 1.3, but you can add in a Config-Class

@Autowired(required = true)
public void configureJackson(ObjectMapper jackson2ObjectMapper) {
    jackson2ObjectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
}

[UPDATE: You must work on the ObjectMapper because the build()-method is called before the config is runs.]

I stumbled upon another solution, which is quite nice.

Basically, only do step 2 from the blog posted mentioned, and define a custom ObjectMapper as a Spring @Component. (Things started working when I just removed all the AnnotationMethodHandlerAdapter stuff from step 3.)

@Component
@Primary
public class CustomObjectMapper extends ObjectMapper {
    public CustomObjectMapper() {
        setSerializationInclusion(JsonInclude.Include.NON_NULL); 
        configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); 
    }
}

Works as long as the component is in a package scanned by Spring. (Using @Primary is not mandatory in my case, but why not make things explicit.)

For me there are two benefits compared to the other approach:

• This is simpler; I can just extend a class from Jackson and don't need to know about highly Spring-specific stuff like Jackson2ObjectMapperBuilder.
• I want to use the same Jackson configs for deserialising JSON in another part of my app, and this way it's very simple: new CustomObjectMapper() instead of new ObjectMapper().

The right way to add further configurations to the Spring Boot peconfigured ObjectMapper is to define a Jackson2ObjectMapperBuilderCustomizer. Else you are overwriting Springs configuration, which you do not want to lose.

 @Configuration
public class MyJacksonConfigurer implements Jackson2ObjectMapperBuilderCustomizer {
    @Override
    public void customize(Jackson2ObjectMapperBuilder builder) {
        builder.deserializerByType(LocalDate.class, new MyOwnJsonLocalDateTimeDeserializer());
    }
}