什么是Feign

Feign 是一個聲明式的偽 Http 客戶端，它使得寫 Http 客戶端變得更簡單。使用 Feign，只需要創建一個接口并注解。它具有可插拔的注解特性，可使用 Feign 注解和 JAX-RS 注解。Feign 支持可插拔的編碼器和解碼器。Feign 默認集成了 Ribbon，Nacos 也很好的兼容了 Feign，默認實現了負載均衡的效果

1. Feign 采用的是基于接口的注解
2. Feign 整合了 ribbon

創建服務者注冊，請參考文章：SpringCloud Alibaba微服務實戰(二) - Nacos服務注冊與發現

構建服務消費者cloud-consumer-feign進行服務調用

1.在父項目中創建子module項目名字為cloud-consumer-feign，在pom中引入nacos服務注冊依賴

<!--Spring web--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!--SpringCloud Alibaba nacos--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency>

完整服務消費者cloud-consumer-feign的pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>cloud-alibaba</artifactId><groupId>com.zsy.springcloud</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>cloud-consumer-feign</artifactId><dependencies><!--Spring web--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!--SpringCloud Alibaba nacos--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build><repositories><!--指定阿里云鏡像庫下載依賴--><repository><id>central</id><name>aliyunmaven</name><url>http://maven.aliyun.com/nexus/content/groups/public/</url></repository></repositories>
</project>

2.配置application.yml或者properties文件

server:port: 8083
spring:#服務應用名字application:name: cloud-consumer-feigncloud:# 指定nacos控制臺地址,配置注冊ip:端口，注意即使是80端口也不可能省略nacos:discovery:server-addr: 127.0.0.1:8848

3.FeignClient接口定義AccountService

package com.zsy.springcloud.service;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import java.util.Map;
@FeignClient("cloud-account")
public interface AccountService {//獲取客戶信息@RequestMapping(value = "/getAccount", method = RequestMethod.GET)public Map<String,Object> getAccount();
}

4.創建消費者AccountConsumerController

package com.zsy.springcloud.controller;
import com.zsy.springcloud.service.AccountService;
import lombok.extern.log4j.Log4j2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import javax.annotation.Resource;
import java.util.HashMap;
import java.util.Map;
@Log4j2
@RestController
public class AccountConsumerController {@Resourceprivate AccountService accountService;@RequestMapping(value = "/getAccount", method = RequestMethod.GET)public Map<String,Object> getAccount() {Map<String,Object> account = new HashMap<>();log.info("---------消費者開始------------");account = accountService.getAccount();log.info("---------消費者結束--------account{}----", account);return account;}
}

5.配置消費者啟動服務的啟動類

package com.zsy.springcloud;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@EnableDiscoveryClient //開啟服務注冊
@EnableFeignClients//開啟feign客戶端
public class FeignConsumerApplication {public static void main(String [] args) {SpringApplication.run(FeignConsumerApplication.class, args);}
}

6.啟動cloud-consumer服務項目，啟動成功，如下圖

7. 驗證服務，瀏覽器訪問http://localhost:8083/getAccount，返回如下圖

查看消費者cloud-consumer控制臺，如下圖

查看服務者cloud-account控制臺，如下圖

碼云地址：https://gitee.com/zlzhaoe/cloud-alibaba

總結

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