Hystrix详解、Feign 使用Hystrix

2022-08-04 09:25:56

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Feign
public 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;
@Component
public 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;

@Component
public 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。