Configured ObjectMapper not used in spring-boot-webflux

Question

I have mixins configured in my objectmapperbuilder config, using the regular spring web controller, the data outputted according to the mixins. However using webflux, a controller with a method returning a Flow or Mono have the data serialized like if the objectmapper a default one.

How to get webflux to enforce an objectmapper configuration to be used ?

sample config:

@Bean
JavaTimeModule javatimeModule(){
    return new JavaTimeModule();
}

@Bean
Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer(){
return jacksonObjectMapperBuilder ->  jacksonObjectMapperBuilder.featuresToEnable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
                                                                    .mixIn(MyClass.class, MyClassMixin.class);
}

Answer 1

I actually found my solution by stepping through the init code:

@Configuration
public class Config {

    @Bean
    JavaTimeModule javatimeModule(){
        return new JavaTimeModule();
    }

    @Bean
    Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer(){
    return jacksonObjectMapperBuilder -> jacksonObjectMapperBuilder.featuresToEnable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
            .mixIn(MyClass.class, MyClassMixin.class);
    }


    @Bean
    Jackson2JsonEncoder jackson2JsonEncoder(ObjectMapper mapper){
       return new Jackson2JsonEncoder(mapper);
    }

    @Bean
    Jackson2JsonDecoder jackson2JsonDecoder(ObjectMapper mapper){
        return new Jackson2JsonDecoder(mapper);
    }

    @Bean
    WebFluxConfigurer webFluxConfigurer(Jackson2JsonEncoder encoder, Jackson2JsonDecoder decoder){
        return new WebFluxConfigurer() {
            @Override
            public void configureHttpMessageCodecs(ServerCodecConfigurer configurer) {
                configurer.defaultCodecs().jackson2JsonEncoder(encoder);
                configurer.defaultCodecs().jackson2JsonDecoder(decoder);
            }
        };

    }
}

Answer 2

I translated the solution of @Alberto Galiana to Java and injected the configured Objectmapper for convenience, so you avoid having to do multiple configurations:

@Configuration
@RequiredArgsConstructor
public class WebFluxConfig implements WebFluxConfigurer {

    private final ObjectMapper objectMapper;

    public void configureHttpMessageCodecs(ServerCodecConfigurer configurer) {
        configurer.defaultCodecs().jackson2JsonEncoder(
            new Jackson2JsonEncoder(objectMapper)
        );

        configurer.defaultCodecs().jackson2JsonDecoder(
            new Jackson2JsonDecoder(objectMapper)
        );
    }
}