?? ?@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(xiàn)的問(wèn)題

在服務(wù)通過(guò)Feign進(jìn)行請(qǐng)求的時(shí)候，傳NULL值引用類型值時(shí)，會(huì)出現(xiàn)類型轉(zhuǎn)換異常，由于HttpMessageConverters直接把NULL轉(zhuǎn)為了""。

解決思路

自定義配置 Spring Cloud Feign Encoder與Decoder

官方文檔說(shuō)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(tǒng)一配置Feign 的Encoder和Decoder的Jackson轉(zhuǎn)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(yīng)用

環(huán)境

nacos: 1.3.1

啟動(dòng)nacos

cd /usr/local/nacos/bin

sh startup.sh -m standalone

自定義Feign的配置

1）添加依賴

加入nacos-discovery發(fā)現(xiàn)服務(wù)的依賴、web、actuator用于監(jiān)控檢查，添加openfeign依賴才能使用Feign功能

2）修改配置文件

配置nacos注冊(cè)中心地址，因?yàn)椴惶峁┓?wù)，所以不需要再注冊(cè)中心注冊(cè)因此register-enabled=false

3）添加Feign支持

配置FeignConfiguration類文件

Spring Cloud Netflix默認(rèn)的SpringMvcController將替換為feign.Contract.Default

用feign.Contract.Default將契約改為Feign原生的默認(rèn)契約，就可以使用feign自帶的注解了

4）自定義Feign接口

Feign接口文件需和啟動(dòng)類再同一包目錄下,使用@FeignClient注解配置所需要調(diào)用服務(wù)，此處nacos-provider是需要在注冊(cè)中心提供服務(wù)

因?yàn)樯厦媾渲昧薴eign.Contract.Deafault,所以在接口中可以使用Feign原生的注解@RequestLine

添加HelloController類文件

此處使用接口MyFeignClient調(diào)用hello方法獲取到nacos-provider客戶端提供的服務(wù)

Feign中記錄日志

1）添加配置項(xiàng)

在配置文件中添加記錄日志的包，* 而每個(gè)FeignClient都需要單獨(dú)配置，它只能響應(yīng)debug級(jí)別的日志

2）設(shè)置日志等級(jí)

在FeignConfiguration類文件中配置日志等級(jí)

日志等級(jí)：

NONE：不記錄（默認(rèn)）
BASIC：只記錄請(qǐng)求方法、URL、響應(yīng)狀態(tài)碼和執(zhí)行時(shí)間
HEADERS：記錄基本信息，請(qǐng)求和響應(yīng)標(biāo)題
FULL：記錄請(qǐng)求和響應(yīng)標(biāo)題、正文和行數(shù)據(jù)

測(cè)試Feign自定義的配置

啟動(dòng)nacos-provider、feign-config客戶端，進(jìn)入nacos查詢nacos-provider服務(wù)是否注冊(cè)

進(jìn)入瀏覽器端鍵入地址http://localhost:2334/hello，就能訪問(wèn)到nacos-provider提供的服務(wù)內(nèi)容

查看日志

控制臺(tái)會(huì)輸出如下信息

[MyFeignClient#hello] <— HTTP/1.1 200 (405ms)
2020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] content-length: 16
2020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] content-type: text/plain;charset=UTF-8
2020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] date: Thu, 13 Aug 2020 08:16:23 GMT
2020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello]
2020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] Hello Gateway A!
2020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] <— END HTTP (16-byte body)

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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