步骤： 1.在配置文件中开启Hystrix 熔断功能：feign.hystrix.eabled:true 2.FeignClient 注解的fallback 和fallbackFactory属性 两种属性都是用于配置响应回退，但是不可以同时使用 fallbackFactory 能够获取OpenFeign 调用抛出的异常

/**
 * <h1>AuthorityFeignClient 后备 fallback</h1>
 * */
@Slf4j
@Component
public class AuthorityFeignClientFallback implements AuthorityFeignClient {

    @Override
    public JwtToken getTokenByFeign(UsernameAndPassword usernameAndPassword) {

        log.info("authority feign client get token by feign request error " +
                "(Hystrix Fallback): [{}]", JSON.toJSONString(usernameAndPassword));
        return new JwtToken("qinyi");
    }
}

/**
 * <h1>与 Authority 服务通信的 Feign Client 接口定义</h1>
 * */
@FeignClient(
        contextId = "AuthorityFeignClient", value = "e-commerce-authority-center",
//        fallback = AuthorityFeignClientFallback.class
        fallbackFactory = AuthorityFeignClientFallbackFactory.class
)
public interface AuthorityFeignClient {

    /**
     * <h2>通过 OpenFeign 访问 Authority 获取 Token</h2>
     * */
    @RequestMapping(value = "/ecommerce-authority-center/authority/token",
            method = RequestMethod.POST,
            consumes = "application/json", produces = "application/json")
    JwtToken getTokenByFeign(@RequestBody UsernameAndPassword usernameAndPassword);
}

/**
 * <h1>OpenFeign 集成 Hystrix 的另一种模式</h1>
 * */
@Slf4j
@Component
public class AuthorityFeignClientFallbackFactory
        implements FallbackFactory<AuthorityFeignClient> {

    @Override
    public AuthorityFeignClient create(Throwable throwable) {

        log.warn("authority feign client get token by feign request error " +
                "(Hystrix FallbackFactory): [{}]", throwable.getMessage(), throwable);

        return new AuthorityFeignClient() {

            @Override
            public JwtToken getTokenByFeign(UsernameAndPassword usernameAndPassword) {
                return new JwtToken("qinyi-factory");
            }
        };
    }
}