How to set custom Jackson ObjectMapper with Spring Cloud Netflix Feign - spring

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());
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;
}
}

Answer 2

follow #NewBie`s answer, i can give the better one...
#Bean
public Decoder feignDecoder() {
return new JacksonDecoder();
}
if you want use jackson message converter in feign client, please use JacksonDecoder, because SpringDecoder will increase average latency of feignclient call in production.
<!-- feign-jackson decoder -->
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-jackson</artifactId>
<version>10.1.0</version>
</dependency>

Answer 3

Define a custom decoder as below, annotated with #Configuration and set as parameter for the feign client interface, configuration = CustomFeignClientConfig.class
#Configuration
public class CustomFeignClientConfig {
#Bean
public Decoder feignDecoder() {
return (response, type) -> {
String bodyStr = Util.toString(response.body().asReader(Util.UTF_8));
JavaType javaType = TypeFactory.defaultInstance().constructType(type);
return new ObjectMapper().readValue( bodyStr, javaType);
};
}
}

Answer 4

#NewBie's answer has serious performance problems. During the new HttpMessageConverters process, loadclass will be performed, resulting in a large number of thread block. If you have used this code, please modify it as follows:
ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(jacksonConverter);
change to
HttpMessageConverters httpMessageConverters = new HttpMessageConverters(jacksonConverter);
ObjectFactory<HttpMessageConverters> objectFactory = () -> httpMessageConverters;
You can use JMeter and Arthas to reproduce this phenomenon, and the modified program has been greatly improved.