1、创建Hystrix-Service服务端

引入依赖：
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.8.RELEASE</version>
        <relativePath/>
    </parent>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <spring-cloud.version>Greenwich.SR2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

启动类配置：
@EnableCircuitBreaker
@EnableDiscoveryClient
@SpringBootApplication
public class HystrixServiceAppRun {
    public static void main(String[] args) {
        SpringApplication.run(HystrixServiceAppRun.class, args);
    }
}

配置文件：
spring:
  application:
    name: hystrix-service
server:
  port: 7004
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://localhost:7001/eureka/
service-url:
  order-service: http://order-service

编写一个测试接口：

@RestController
@RequestMapping("/order")
public class OrderHystrixController {

    @Autowired
    private OrderService orderService;

    @GetMapping("/testFallback/{id}")
    public CommonResult testFallbackOrder(@PathVariable Long id) {
        return orderService.getOrder(id);
    }
}

Service层代码：
@Service
public class OrderServiceImpl implements OrderService {

    @Autowired
    private RestTemplate restTemplate;

    @Value("${service-url.order-service}")
    private String orderServiceUrl;

    @HystrixCommand(fallbackMethod = "getDefaultOrder")
    @Override
    public CommonResult getOrder(Long id) {
        return restTemplate.getForObject(orderServiceUrl + "/order/{1}", CommonResult.class, id);
    }

    public CommonResult getDefaultOrder(@PathVariable Long id) {
        Order defaultOrder = new Order();
        defaultOrder.setOrderId(999L);
        defaultOrder.setOrderName("华为手机");
        return new CommonResult<>(defaultOrder);
    }

}

启动eureka-server服务
启动order-service服务
启动hystrix-service服务

2、接口测试

调用此接口：[http://localhost:7004/order/testFallback/1](http://localhost:7004/order/testFallback/1)

然后将Order-service服务关闭，测试降级：