Spring Cloud 之 Feign Client服务消费（六）

上一篇讲了Ribbon的使用，会发现其实Ribbon的使用还是比较繁琐的，其实微服务系统内部调用一般都是通过Feign完成调用的。本篇讲一下Feign。

1、创建一个module名称为x-demo-service-ribbon的ribbon服务

2、build.gradle中加入依赖

dependencies {
    compile("org.springframework.cloud:spring-cloud-starter-netflix-eureka-client")
    compile("org.springframework.cloud:spring-cloud-starter-openfeign")
}

3、创建Service层

注意第7行value配置，必须和x-demo-service中定义的接口path一致

/**
 * @author Leo
 */
@FeignClient(value = "x-demo-service")
public interface FeignClientDemoService {

    @RequestMapping(value = "demo/service", method = RequestMethod.GET)
    String service();
}

4、创建Controller层

@RestController
@RequestMapping("feign")
public class FeignClientDemoController {

    @Autowired
    FeignClientDemoService feignClientDemoService;

    @RequestMapping(value = "service", method = RequestMethod.GET)
    public String service() {
        return feignClientDemoService.service();
    }
}

5、bootstrap.yml配置

spring:
  application:
    name: x-demo-service-feign

server:
  port: 8092

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/,http://localhost:8762/eureka/,http://localhost:8763/eureka/

6、创建启动类

/**
 * @author Leo
 */
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class FeignServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(FeignServerApplication.class, args);
    }
}

7、启动服务，验证Feign调用

浏览器中输入：http://localhost:8092/feign/service，多次刷新后会返回如下结果：

x-demo-service hello.8081

x-demo-service hello.8082

x-demo-service hello.8083

至此，说明我们的Feign调用已经完成。通过同一个接口访问，会访问到8081,8082,8083三个不同的服务提供者。

同时可以注意到后台日志输出：

2021-02-23 13:50:12.655  INFO 54776 --- [nio-8092-exec-1] c.n.l.DynamicServerListLoadBalancer      : DynamicServerListLoadBalancer for client x-demo-service initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=x-demo-service,current list of Servers=[windows10.microdone.cn:8082, windows10.microdone.cn:8081, windows10.microdone.cn:8083],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone;    Instance count:3;    Active connections count: 0;    Circuit breaker tripped count: 0;    Active connections per server: 0.0;]
},Server stats: [[Server:windows10.microdone.cn:8082;    Zone:defaultZone;    Total Requests:0;    Successive connection failure:0;    Total blackout seconds:0;    Last connection made:Thu Jan 01 08:00:00 CST 1970;    First connection made: Thu Jan 01 08:00:00 CST 1970;    Active Connections:0;    total failure count in last (1000) msecs:0;    average resp time:0.0;    90 percentile resp time:0.0;    95 percentile resp time:0.0;    min resp time:0.0;    max resp time:0.0;    stddev resp time:0.0]
, [Server:windows10.microdone.cn:8083;    Zone:defaultZone;    Total Requests:0;    Successive connection failure:0;    Total blackout seconds:0;    Last connection made:Thu Jan 01 08:00:00 CST 1970;    First connection made: Thu Jan 01 08:00:00 CST 1970;    Active Connections:0;    total failure count in last (1000) msecs:0;    average resp time:0.0;    90 percentile resp time:0.0;    95 percentile resp time:0.0;    min resp time:0.0;    max resp time:0.0;    stddev resp time:0.0]
, [Server:windows10.microdone.cn:8081;    Zone:defaultZone;    Total Requests:0;    Successive connection failure:0;    Total blackout seconds:0;    Last connection made:Thu Jan 01 08:00:00 CST 1970;    First connection made: Thu Jan 01 08:00:00 CST 1970;    Active Connections:0;    total failure count in last (1000) msecs:0;    average resp time:0.0;    90 percentile resp time:0.0;    95 percentile resp time:0.0;    min resp time:0.0;    max resp time:0.0;    stddev resp time:0.0]
]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@7655c176

看到这个日志，是不是想起了Ribbon，没错！Feign底层就是封装了Ribbon实现的负载均衡，而Feign只是一种声明式的服务调用。