Customizable Jackson ObjectMapper in WebFluxConfigurationSupport [SPR-15247]

[spring-projects-issues]

Attila Király opened SPR-15247 and commented

Currently WebFluxConfigurationSupport (in its addDefaultHttpMessageReaders and addDefaultHttpMessageWriters methods) creates ObjectMapper-s indirectly through the new Jackson2JsonDecoder() and new Jackson2JsonEncoder() calls.

These ObjectMapper-s are not passed through any hooks which would make it possible to customize them (for example to disable SerializationFeature.WRITE_DATES_AS_TIMESTAMPS).

The only way I could customize it (and still keep the default writers added) was to create a custom WebFluxConfigurer:

@Component
public class Jackson2WebFluxReConfigurer implements WebFluxConfigurer {

  @Override
  public void extendMessageWriters(List<HttpMessageWriter<?>> writers) {
    writers.removeIf(Jackson2ServerHttpMessageWriter.class::isInstance);

    List<Encoder<?>> sseDataEncoders = new ArrayList<>();
    Jackson2JsonEncoder encoder = new Jackson2JsonEncoder(
        Jackson2ObjectMapperBuilder.json().featuresToDisable(
            SerializationFeature.WRITE_DATES_AS_TIMESTAMPS).build());
    writers.add(new Jackson2ServerHttpMessageWriter(encoder));
    sseDataEncoders.add(encoder);
    HttpMessageWriter<Object> writer = new ServerSentEventHttpMessageWriter(sseDataEncoders);
    writers.add(new Jackson2ServerHttpMessageWriter(writer));
  }
}

It would be great if (for example) WebFluxConfigurer had a callback method to customize the ObjectMapper (or anytlhing equivalent with this).

---

Affects: 5.0 M4

Issue Links:

• #19977 Use ServerCodecConfigurer in HandlerStrategies

Referenced from: commits f8a21ab, 4a7218f, dc3851d

[spring-projects-issues]

Rossen Stoyanchev commented

This will definitely require some kind of improvement, thanks for raising it. I'm postponing till RC1 since we need to a broader review of the message reading and writing and how it's configured.

[spring-projects-issues]

Attila Király commented

Thanks for looking into this.

It would be also nice if - whatever the improvement will be - it was possible to use that with spring boots jackson support (the spring.jackson.* properties).

[spring-projects-issues]

Rossen Stoyanchev commented

WebFluxConfigurer now exposes a ServerCodecConfigurer with the method exposing it, configureHttpMessageCodecs, essentially taking the place of the addMessageReaders, addMessageWriters, extendMessageReaders, and extendMessageWriters methods. The new configurer makes it easy to replace the built-in Jackson encoder/decoder.