How to set custom Jackson ObjectMapper with Spring Cloud Netflix Feign

Question

I'm running into a scenario where I need to define a one-off @FeignClient for a third party API. In this client I'd like to use a custom Jackson ObjectMapper that differs from my @Primary one. I know it is possible to override spring's feign configuration defaults however it is not clear to me how to simply override the ObjectMapper just by this specific client.

Answer 1

Per the documentation, you can provide a custom decoder for your Feign client as shown below.

Feign Client Interface:

@FeignClient(value = "foo", configuration = FooClientConfig.class)
public interface FooClient{
    //Your mappings
}

Feign Client Custom Configuration:

@Configuration
public class FooClientConfig {

    @Bean
    public Decoder feignDecoder() {
        HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter(customObjectMapper());
        ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(jacksonConverter);
        return new ResponseEntityDecoder(new SpringDecoder(objectFactory));
    }

    public ObjectMapper customObjectMapper(){
        ObjectMapper objectMapper = new ObjectMapper();
        //Customize as much as you want
        return objectMapper;
    }
}