spring - 如何使用 Spring Cloud Netflix Feign 设置自定义 Jackson ObjectMapper

Question

我遇到了一种情况，我需要为第三方 API 定义一次性的 @FeignClient。在这个客户端中，我想使用与我的@Primary 不同的自定义 Jackson ObjectMapper。我知道可以覆盖 spring 的 feign 配置默认值，但是我不清楚如何仅通过这个特定的客户端简单地覆盖 ObjectMapper。

Answer 1

根据文档，您可以为您的 Feign 客户端提供自定义解码器，如下所示。

Feign客户端界面：

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

Feign 客户端自定义配置：

@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

@NewBie 的回答存在严重的性能问题。在此new HttpMessageConverters过程中，会执行loadclass，导致大量线程阻塞。如果您使用过此代码，请修改如下：

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

改成

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

可以使用JMeter和Arthas来重现这种现象，修改后的程序有了很大的改进。

Answer 4

如下定义一个自定义解码器，注释@Configuration并设置为 feign 客户端接口的参数，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);
        };
    }
}