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在Feign 接口中定义了依赖服务的接口，当Feign调用依赖服务的接口失败时怎么办？
我们也可以在Feign中利用Hystrix的功能，当Feign 调用依赖服务的接口失败时，通过Hystrix调用指定的方法,Spring Cloud默认为Feign整合了Hystrix，但在Spring Cloud 基于Spring boot 2.x的版本中，默认是Feign是关闭Hystrix的。
那么Feign与Hystrix怎么配合使用呢？

1、创建项目futurecloud-feign-hystrix
注意：不需要添加依赖spring-cloud-starter-netflix-hystrix，Spring Cloud默认已为Feign整合了Hystrix。spring boot 主函数也不需要添加注解@EnableCircuitBreaker 来开启Hystrix。主函数类如下：

package com.futurecloud.feignhystrix;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.netflix.eureka.EnableEurekaClient;import org.springframework.cloud.openfeign.EnableFeignClients;import org.springframework.context.annotation.Bean;import org.springframework.web.client.RestTemplate;@SpringBootApplication@EnableEurekaClient //声明为eureka 客户端@EnableFeignClients //启动Feignpublic class FuturecloudFeignHystrixApplication{ @Bean //相当于xml中的bean标签，主要是用于调用当前方法获取到指定对象 public RestTemplate getRestTemplate(){ return new RestTemplate(); } public static void main( String[] args ) { SpringApplication.run(FuturecloudFeignHystrixApplication.class,args); }}

开启Hystrix在application.yml中配置

#开启hystrix配置feign: hystrix: enabled: true

2、Feign 使用fallback 方式进行Hystrix的回退
在定义Feign接口时，我们可以指定Feign接口中的方法调用失败后的一个回调类，这个类实现此Feign接口，
Feign接口代码如下：

package com.futurecloud.feignhystrix.feign;import com.futurecloud.feignhystrix.bean.User;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;@FeignClient(name = "futurecloud-user",fallback = FeignHystrixFallback.class) //指定依赖服务Hystrixd的回调类public interface FeignInterface { @GetMapping("/user/{id}") User getUser(@PathVariable("id") Long id); @GetMapping("/getObject") User getObject(User user); @GetMapping("/find//user/{id}") User findUser(@PathVariable("id") Long id);}

FeignHystrixFallback 代码如下：

package com.futurecloud.feignhystrix.feign;import com.futurecloud.feignhystrix.bean.User;import org.springframework.stereotype.Component;import java.util.Date;@Componentpublic class FeignHystrixFallback implements FeignInterface{ @Override public User getUser(Long id) { User user = new User(); user.setId(-401L); user.setUsername("01-feignHystrixFallback"); user.setMail("hystrix-fallback@sina.com"); user.setPhone("13838389438"); user.setCreateDate(new Date()); return user; } @Override public User getObject(User user) { user = new User(); user.setId(-402L); user.setUsername("02-feignHystrixFallback"); user.setMail("hystrix-fallback@sina.com"); user.setPhone("13838389438"); user.setCreateDate(new Date()); return user; } @Override public User findUser(Long id) { User user = new User(); user.setId(-403L); user.setUsername("03-feignHystrixFallback"); user.setMail("hystrix-fallback@sina.com"); user.setPhone("13838389438"); user.setCreateDate(new Date()); return user; }}

注意：要添加注解@Component，否则Spring boot 找不到这个bean

启动eureka 服务futurecloud-service，
启动服务提供者服务futurecloud-user，
启动此服务futurecloud-feign-hystrix
访问http://localhost:8907/order/20 ,成功访问
将服务futurecloud-user关掉，再一次访问http://localhost:8907/order/20，调用了fallback指定的FeignHystrixFallback中的方法。

3、Feign 使用fallbackFactory方式进行Hystrix的回退
在Feign接口中指定使用fallbackFactory工厂类，其实就是实现Feign接口的匿名类

Feign接口定义如下：

package com.futurecloud.feignhystrix.feign;import com.futurecloud.feignhystrix.bean.User;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;@FeignClient(name = "futurecloud-user",fallbackFactory = FeignHystrixFallbackFactory.class)public interface FeignInterface { @GetMapping("/user/{id}") User getUser(@PathVariable("id") Long id); @GetMapping("/getObject") User getObject(User user); @GetMapping("/find//user/{id}") User findUser(@PathVariable("id") Long id);}

FeignHystrixFallbackFactory代码如下：

package com.futurecloud.feignhystrix.feign;import com.futurecloud.feignhystrix.bean.User;import feign.hystrix.FallbackFactory;import org.springframework.stereotype.Component;import java.util.Date;@Componentpublic class FeignHystrixFallbackFactory implements FallbackFactory<FeignInterface>{ @Override public FeignInterface create(Throwable throwable) { return new FeignInterface() { @Override public User getUser(Long id) { User user = new User(); user.setId(-404L); user.setUsername("01-feignHystrixFallbackFactory"); user.setMail("hystrix-fallback@sina.com"); user.setPhone("13838389438"); user.setCreateDate(new Date()); return user; } @Override public User getObject(User user) { user = new User(); user.setId(-405L); user.setUsername("02-feignHystrixFallbackFactory"); user.setMail("hystrix-fallback@sina.com"); user.setPhone("13838389438"); user.setCreateDate(new Date()); return user; } @Override public User findUser(Long id) { User user = new User(); user.setId(-406L); user.setUsername("03-feignHystrixFallbackFactory"); user.setMail("hystrix-fallback@sina.com"); user.setPhone("13838389438"); user.setCreateDate(new Date()); return user; } }; }}

其余配置与fallback一致。