Configured ObjectMapper not used in spring-boot-webflux - spring-boot

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)
);
}
}

Answer 3

Just implement WebFluxConfigurer and override method configureHttpMessageCodecs
Sample code for Spring Boot 2 + Kotlin
#Configuration
#EnableWebFlux
class WebConfiguration : WebFluxConfigurer {
override fun configureHttpMessageCodecs(configurer: ServerCodecConfigurer) {
configurer.defaultCodecs().jackson2JsonEncoder(Jackson2JsonEncoder(ObjectMapper()
.setSerializationInclusion(JsonInclude.Include.NON_EMPTY)))
configurer.defaultCodecs().jackson2JsonDecoder(Jackson2JsonDecoder(ObjectMapper()
.enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)))
}
}
Make sure all your data classes to be encoded/decoded have all its properties annotated with #JsonProperty even if property name is equal in class and json data
data class MyClass(
#NotNull
#JsonProperty("id")
val id: String,
#NotNull
#JsonProperty("my_name")
val name: String)

Answer 4

In my case, I was trying to use a customized ObjectMapper while inheriting all of the behavior from my app's default WebClient.
I found that I had to use WebClient.Builder.codecs. When I used WebClient.Builder.exchangeStrategies, the provided overrides were ignored. Not sure if this behavior is something specific to using WebClient.mutate, but this is the only solution I found that worked.
WebClient customizedWebClient = webClient.mutate()
.codecs(clientCodecConfigurer ->
clientCodecConfigurer.defaultCodecs()
.jackson2JsonDecoder(new Jackson2JsonDecoder(customObjectMapper)))
.build();

Answer 5

I have tried all the different solutions (#Primary #Bean for ObjectMapper, configureHttpMessageCodecs(), etc.). What worked for me at the end was specifying a MIME type. Here's an example:
#Configuration
class WebConfig: WebFluxConfigurer {
override fun configureHttpMessageCodecs(configurer: ServerCodecConfigurer) {
val encoder = Jackson2JsonEncoder(objectMapper, MimeTypeUtils.APPLICATION_JSON)
val decoder = Jackson2JsonDecoder(objectMapper, MimeTypeUtils.APPLICATION_JSON)
configurer.defaultCodecs().jackson2JsonEncoder(encoder)
configurer.defaultCodecs().jackson2JsonDecoder(decoder)
}
}