springcloud项目创建笔记8 之《feign客户端》

在springboot中，我们使用restTemplate来发送http请求。而在springcloud中，提供了feign客户端

1、建立一个内部应用mycloud-inside-app1，提供controller调用类InsideApp1Resource.java

package com.example.mycloud.resource;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/insideApp1")
public class InsideApp1Resource {

	@GetMapping("/remoteApi/{id}")
	public String remoteApi(@PathVariable String id) {
		return "hello:"+id;
	}
}

测试：http://localhost:8015/insideApp1/remoteApi/123
返回：hello:123

2、添加依赖包
修改mycloud-service-provider1模块pom.xml

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

3、启动类添加注解@EnableFeignClients
注意包扫描路径

@EnableDiscoveryClient
@SpringBootApplication
@ComponentScan("com.example.mycloud")
@EnableFeignClients("com.example.mycloud")
public class ServiceProvider1Application {
	public static void main(String[] args) {
        SpringApplication.run(ServiceProvider1Application.class, args);
    }
}

4、application.yml文件添加feign配置

#feign client配置
feign:
  client:
    config:
      #或者为想要调用的微服务名称
      default:
        connectTimeout: 30000
        readTimeout: 30000
        loggerLevel: basic
  okhttp:
    #使用okhttp作为client
    enabled: true
  hystrix:
    #禁用hystrix
    enabled: false

5、添加包com.example.mycloud.feign，在包下添加
客户端调用接口类FeignClientService.java，其中inside-app1表示内部应用mycloud-inside-app1在eureka注册时的服务名称

package com.example.mycloud.feign;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(name = "inside-app1")
public interface FeignClientService {
	
	@GetMapping("/insideApp1/remoteApi/{id}")
	public String remoteApi(@PathVariable String id);
}

6、添加测试controller，FeginTestResource.java

package com.example.mycloud.resource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import com.example.mycloud.feign.FeignClientService;

@RestController
public class FeginTestResource {

	@Autowired
	FeignClientService feignClientService;
	
	@GetMapping("/feginTest/{id}")
	public String feginTest(@PathVariable String id) {
		return feignClientService.remoteApi(id);
	}
}

7、报错com.netflix.client.ClientException: Load balancer does not have available server for client: inside-app1
需要在application.yml文件中修改eureka client的配置：
fetchRegistry: true
因为原来是false，就不会从注册中心拉取服务列表

8、测试
启动模块：
mycloud-eureka
mycloud-inside-app1
mycloud-service-provider1
访问浏览器：
http://localhost:8011/feginTest/233
返回：
hello:233

9、初始化日志

2021-03-04 21:00:04.537  INFO 19708 --- [nio-8011-exec-2] c.netflix.config.ChainedDynamicProperty  : Flipping property: inside-app1.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2021-03-04 21:00:04.552  INFO 19708 --- [nio-8011-exec-2] c.n.u.concurrent.ShutdownEnabledTimer    : Shutdown hook installed for: NFLoadBalancer-PingTimer-inside-app1
2021-03-04 21:00:04.552  INFO 19708 --- [nio-8011-exec-2] c.netflix.loadbalancer.BaseLoadBalancer  : Client: inside-app1 instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=inside-app1,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null
2021-03-04 21:00:04.558  INFO 19708 --- [nio-8011-exec-2] c.n.l.DynamicServerListLoadBalancer      : Using serverListUpdater PollingServerListUpdater
2021-03-04 21:00:04.572  INFO 19708 --- [nio-8011-exec-2] c.netflix.config.ChainedDynamicProperty  : Flipping property: inside-app1.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2021-03-04 21:00:04.573  INFO 19708 --- [nio-8011-exec-2] c.n.l.DynamicServerListLoadBalancer      : DynamicServerListLoadBalancer for client inside-app1 initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=inside-app1,current list of Servers=[localhost:8015],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone;	Instance count:1;	Active connections count: 0;	Circuit breaker tripped count: 0;	Active connections per server: 0.0;]
},Server stats: [[Server:localhost:8015;	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@38ccb981

参考资料：
https://github.com/OpenFeign/feign
https://spring.io/projects/spring-cloud-openfeign
https://www.imooc.com/article/299674

注：最新代码上传至https://github.com/csj50/mycloud