3. Feign 简介

Spring Cloud Feign整合了Spring Cloud Ribbon与Spring Cloud Hystrix，除提供两者强大功能外，提供了一种声明式的web服务客户端定义方式。只用使用注解便能轻松使用Feign客户端。

3.1. 快速入门

1.创建一个Spring boot项目，命名为hello-service，在pom.xml中添加Hystrix依赖:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-feign</artifactId>
</dependency>

2.在主类中使用@EnableFeignClients注解开启Feign功能支持:

@EnableFeignClients
@EnableDiscoveryClient
@SpringBooApplication
public class ConsumerApplication{

    public static void main(String[] args){

        SpringApplication.run(ConsumerApplication.class, args);

    }

}

3.定义SslmRemoteService接口，通过@FeignClient的value属性指定服务名来绑定服务，fallback属性指定服务降级调用方法类，path属性指定公共的URL:

@FeignClient(value = "srm-supplier-lifecycle", fallback = SslmRemoteServiceFallback.class, path = "/v1/{organizationId}")
public interface SslmRemoteService{

    /**
    *创建调查表头并发布调查表
    *
    * @param organizationId
    * @param investigateHeaderList
    * @return List<InvestigateHeaderVO>
    */
    @PostMapping("/investigate/save-release")
    List<InvestigateHeaderVO> batchSaveAndReleaseInvestgHeader(@PathVariable("organizationId") Long organizationId,
                                                                @RequestBody List<InvestigateHeaderVO> investigateHeaderList);


}

4.定义SslmRemoteServiceFallback回调方法类:

@Component
@SuppressWarnings("all")
public class SslmRemoteServiceFallback implements SslmRemoteService{

    private static final Logger LOGGER = LoggerFactory.getLogger(SslmRemoteServiceFallback.class);

    @Override
    public List<InvestigateHeaderVO> batchSaveAndReleaseInvestgHeader(Long organizationId, List<InvestigateHeaderVO> investigateHeaderList) {
        LOGGER.error("Post batch save and release investgHeader fail");
        throw new CommonException(BaseConstants.ErrorCode.ERROR);
    }
}

4. Feign 属性配置

Spring Cloud Feign整合了Spring Cloud Ribbon和Spring Cloud Hystrix，所以对于负载均衡、熔断降级的配置可以按Ribbon和Hystrix的配置。

4.1. Ribbon配置

@FeignClient中name或value属性指定的服务名即Ribbon客户端的名，因此Feign中想对不同客户端做不同配置可以根据<client>.ribbon.key=value进行配置

4.2. Hystrix配置

feign.hystrix.enabled: 设置是否开启Feign 客户端Hystrix支持。

4.3. 禁用Hystrix配置

除通过feign.hystrix.enabled设置外还可针对服务客户端关闭Hystrix支持

1.创建关闭Hystrix配置类:

@Configuration
public class DisableHystrixConfiguration{

    @Bean
    @Scope("prototype")
    public Feign.Builder feignBuilder(){
        return Feign.builder();
    }

}

2.通过@FeignClient注解中，configuration参数引入配置:

@FeignClient(value = "hello-service", configuration = DisableHystrixConfiguration.class)
public interface HelloService{

}

4.4. Feign配置属性

feign.compression.request.enabled: 设置是否开启请求GZIP压缩功能 feign.compression.response.enabled: 设置是否开启响应GZIP压缩功能 feign.compression.request.mime-type: 设置GZIP压缩请求的类型，默认text/xml,application/xml,application/json feign.compression.request.min-request-size: 设置GZIP压缩请求大小下限，超过的请求将被压缩