[FIXED] How to set custom Jackson ObjectMapper with Spring Cloud Netflix Feign

Issue

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.

Solution

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());

        HttpMessageConverters httpMessageConverters = new HttpMessageConverters(jacksonConverter);
        ObjectFactory<HttpMessageConverters> objectFactory = () -> httpMessageConverters;


        return new ResponseEntityDecoder(new SpringDecoder(objectFactory));
    }

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

Answered By - Newbie
Answer Checked By - Marilyn (JavaFixing Volunteer)