SpringCloud Feign Jackson自定义配置方式

SpringCloud Feign Jackson自定义配置方式

目录FeignJackson自定义配置出现的问题解决思路解决方法Feign自定义配置应用环境自定义Feign的配置Feign中记录日志测试Feign自定义的配置查看日志

Feign Jackson自定义配置

Spring Cloud Feign 默认支持Spring MVC的注解 使用相同的HttpMessageConverters类转换

官方文档说明：

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

但是我们一般在返回给前端jsON格式的时候 都会把相应的 NULL值转为相应的""，这使得Spring Cloud Feign也使用相同的Jackson配置，例如我们项目的配置

@Bean

public ObjectMapper jacksonObjectMapper() {

ObjectMapper objectMapper = new ObjectMapper();

// objectMapper.setSerializationInclusion(Include.NON_NULL);

objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer

@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;

}

出现的问题

在服务通过Feign进行请求的时候，传NULL值引用类型值时，会出现类型转换异常，由于HttpMessageConverters直接把NULL转为了""。

解决思路

自定义配置 Spring Cloud Feign Encoder与Decoder

官方文档说明：

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.

解决方法

统一配置Feign 的Encoder和Decoder的Jackson转换方式

import com.fasterxml.jackson.databind.DeserializationFeature;

import KohwMvMEVlcom.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 objectFactory = () -> new HttpMessageConverters(jacksonConverter);

return new ResponseEntityDecoder(new SpringDecoder(objectFactory));

}

@Bean

public Encoder feignEncoder(){

HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter(customObjectMapper());

ObjectFactory 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 不起作用可以试试这种方式

public ObjectMapper customObjectMapper(){

ObjectMapper objectMapper = new ObjectMapper();

//Customize as much as you want

objectMapper.registerModule(new StringSanitizerModule());

return objectMapper;

}

public class Stringhttp://SanitizerModule extends SimpleModule {

public StringSanitizerModule() {

addDeserializer(String.class, new StdScalarDeserializer(String.class) {

@Override

public String deserialize(JsonParser jsonParser, DeserializationContext ctx) throws IOException {

return StringUtils.trimToNull(jsonParser.getValueAsString());

}

});

}

}

Feign自定义配置应用

环境

nacos: 1.3.1

启动nacos

cd /usr/local/nacos/bin

sh startup.sh -m standalone

自定义Feign的配置

1）添加依赖

加入nacos-discovery发现服务的依赖、web、actuator用于监控检查，添加openfeign依赖才能使用Feign功能

2）修改配置文件

配置nacos注册中心地址，因为不提供服务，所以不需要再注册中心注册因此register-enabled=false

3）添加Feign支持

配置FeignConfiguration类文件

Spring Cloud Netflix默认的SpringMvcController将替换为feign.Contract.Default

用feign.Contract.Default将契约改为Feign原生的默认契约，就可以使用feign自带的注解了

4）自定义Feign接口

Feign接口文件需和启动类再同一包目录下,使用@FeignClient注解配置所需要调用服务，此处nacos-provider是需要在注册中心提供服务

因为上面配置了feign.Contract.Deafault,所以在接口中可以使用Feign原生的注解@RequestLine

添加HelloController类文件

此处使用接口MyFeignClient调用hello方法获取到nacos-provider客户端提供的服务

Feign中记录日志

1）添加配置项

在配置文件中添加记录日志的包，* 而每个FeignClient都需要单独配置，它只能响应debug级别的日志

2）设置日志等级

在FeignConfiguration类文件中配置日志等级

日志等级：

NONE：不记录（默认）BASIC：只记录请求方法、URL、响应状态码和执行时间HEADERS：记录基本信息，请求和响应标题FULL： 记录请求和响应标题、正文和行数据

测试Feign自定义的配置

启动nacos-provider、feign-config客户端，进入nacos查询nacos-provider服务是否注册

进入浏览器端键入地址http://localhost:2334/hello，就能访问到nacos-provider提供的服务内容

查看日志

控制台会输出如下信息

[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: 162020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] content-type: text/plain;charset=UTF-82020-08-13 16:16:23.021 DEBUG 3680 — [nio-2334-exec-1] com.kk.feign.MyFeignClient : [MyFeignClient#hello] date: Thu, 13 Aug 2020 08:16:23 GMT2020-08-13 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)

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