SpringCloud?Feign?Jackson自定義配置的方法

發布時間：2022-03-17 09:09:47 來源：億速云閱讀：709 作者：iii 欄目：開發技術

今天小編給大家分享一下SpringCloud Feign Jackson自定義配置的方法的相關知識點，內容詳細，邏輯清晰，相信大部分人都還太了解這方面的知識，所以分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后有所收獲，下面我們一起來了解一下吧。

Feign Jackson自定義配置

Spring Cloud Feign 默認支持Spring MVC的注解使用相同的HttpMessageConverters類轉換

官方文檔說明：

Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web.

但是我們一般在返回給前端JSON格式的時候都會把相應的 NULL值轉為相應的""，這使得Spring Cloud Feign也使用相同的Jackson配置，例如我們項目的配置

    @Bean
    public ObjectMapper jacksonObjectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        // objectMapper.setSerializationInclusion(Include.NON_NULL);
        objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
            @Override
            public void serialize(Object value, JsonGenerator jg, SerializerProvider sp)
                throws IOException, JsonProcessingException {
                jg.writeString("");
                sp.getDefaultNullKeySerializer();
            }
        });
        objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
        return objectMapper;
    }

出現的問題

在服務通過Feign進行請求的時候，傳NULL值引用類型值時，會出現類型轉換異常，由于HttpMessageConverters直接把NULL轉為了""。

解決思路

自定義配置 Spring Cloud Feign Encoder與Decoder

官方文檔說明：

Spring Cloud Netflix provides the following beans by default for feign (BeanType beanName: ClassName):Decoder feignDecoder: ResponseEntityDecoder (which wraps a SpringDecoder)Encoder feignEncoder: SpringEncoderLogger feignLogger: Slf4jLoggerContract feignContract: SpringMvcContractFeign.Builder feignBuilder: HystrixFeign.BuilderClient feignClient: if Ribbon is enabled it is a LoadBalancerFeignClient, otherwise the default feign client is used.

解決方法

統一配置Feign 的Encoder和Decoder的Jackson轉換方式

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
import org.springframework.cloud.openfeign.support.ResponseEntityDecoder;
import org.springframework.cloud.openfeign.support.SpringDecoder;
import org.springframework.cloud.openfeign.support.SpringEncoder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import feign.codec.Decoder;
import feign.codec.Encoder;
@Configuration
public class CustomFeignConfig {
    @Bean
    public Decoder feignDecoder() {
        HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter(customObjectMapper());
        ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(jacksonConverter);
        return new ResponseEntityDecoder(new SpringDecoder(objectFactory));
    }
    @Bean
    public Encoder feignEncoder(){
        HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter(customObjectMapper());
        ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(jacksonConverter);
        return new SpringEncoder(objectFactory);
    }
    public ObjectMapper customObjectMapper(){
        ObjectMapper objectMapper = new ObjectMapper();
        //Customize as much as you want
        objectMapper.configure(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true);
        return objectMapper;
    }
}

如果配置DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT 不起作用可以試試這種方式

public ObjectMapper customObjectMapper(){
        ObjectMapper objectMapper = new ObjectMapper();
        //Customize as much as you want
        objectMapper.registerModule(new StringSanitizerModule());
        return objectMapper;
}
public class StringSanitizerModule extends SimpleModule {
    public StringSanitizerModule() {
        addDeserializer(String.class, new StdScalarDeserializer<String>(String.class) {
            @Override
            public String deserialize(JsonParser jsonParser, DeserializationContext ctx) throws IOException {
               return StringUtils.trimToNull(jsonParser.getValueAsString());
            }
        });
    }
}

Feign自定義配置應用

環境

nacos: 1.3.1

啟動nacos

cd /usr/local/nacos/bin

sh startup.sh -m standalone