上一章中完成了Ribbon和hytrix的整合，本章整合Hystrix和Feign

要实现Hystrix和Feign的整合，需要在消费端完成以下几个步骤:

1.添加Hystrix和Feign的maven依赖

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

2.在启动类中添加注解

@EnableFeignClients
@EnableCircuitBreaker

3.添加FeignClient接口

package com.example.demo.feign;
@FeignClient(name="spring-cloud-provider",fallback=UserFeignClientFallback.class)
public interface UserFeignClient {
    @RequestMapping(value="/user/get?id={id}",method=RequestMethod.GET)
    public User get(@PathVariable("id") String id);
    @RequestMapping(value="/user/list",method=RequestMethod.GET)
    public List<User>  list();
}

4.添加Fallback的实现了，Fallback实现了FeignClient接口

package com.example.demo.fallback;
@Component
public class UserFeignClientFallback implements UserFeignClient{
    @Override
    public User get(String id) {
        // TODO Auto-generated method stub
        return new User();
    }
    @Override
    public List<User> list() {
        // TODO Auto-generated method stub
        return new ArrayList<User>();
    }
}

5.使用FeignClient实现对微服务的调用

//只需要在使用的SpringBean中注入Feignclient即可
@Autowired
private UserFeignClient userFeignClient;

使用fallbackFactory实现Hystrix和Feign的整合，并且捕获异常

UserFeignClient.java

把@FeignClient的fallback属性给删除了,并且添加fallbackFactory=UserFeignClientFactory.class

package com.example.demo.feign;
@FeignClient(name="spring-cloud-provider"/*,fallback=UserFeignClientFallback.class*/,fallbackFactory=UserFeignClientFactory.class)
public interface UserFeignClient {

    @RequestMapping(value="/user/get?id={id}",method=RequestMethod.GET)
    public User get(@PathVariable("id") String id);

    @RequestMapping(value="/user/list",method=RequestMethod.GET)
    public List<User>  list();

}

UserFeignClientFactory.java

package com.example.demo.fallback;
@Component
public class UserFeignClientFactory implements FallbackFactory<UserFeignClient>{

    @Override
    public UserFeignClient create(Throwable arg0) {
        //返回一个匿名内部类,这个匿名内部类实现了FeignClient接口
        return new UserFeignClient(){

            @Override
            public User get(String id) {
                // TODO Auto-generated method stub
                return new User("-1", "error", -1, new Date());
        }
            @Override
            public List<User> list() {
                // TODO Auto-generated method stub
                return new ArrayList<User>();
            }};
    }

}

验证

关闭微服务，浏览器打开http://192.168.88.101:9000/user/feign_get?id=1，在消费端被浏览器调用的时候

浏览器显示如下内容:

{"id":"-1","userName":"error","age":-1,"birthday":1503539977737}

系统抛出下面的异常

java.lang.RuntimeException: com.netflix.client.ClientException: Load balancer does not have available server for client: spring-cloud-provider
    at org.springframework.cloud.netflix.feign.ribbon.LoadBalancerFeignClient.execute(LoadBalancerFeignClient.java:71)
    at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:97)
    at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76)
    at feign.hystrix.HystrixInvocationHandler$1.run(HystrixInvocationHandler.java:108)