SpringCloud系列之声明式服务调用Netflix Feign

一时失言乱红尘 2021-09-02 03:11 435阅读 0赞

在[上一章][Link 1]的学习中，我们知道了微服务的基本概念，知道怎么基于Ribbon+restTemplate的方式实现服务调用，接着上篇博客，我们学习怎么基于Feign实现服务调用，请先学习上篇博客，然后再学习本篇博客

Feign是一个声明式的web service客户端，它使得编写web service客户端更为容易。创建接口，为接口添加注解，即可使用Feign。Feign可以使用Feign注解或者JAX-RS注解，还支持热插拔的编码器和解码器。

环境准备：

*  JDK 1.8
 *  SpringBoot2.2.3
 *  SpringCloud(Hoxton.SR6)
 *  Maven 3.2+
 *  开发工具
    
     *  IntelliJ IDEA
     *  smartGit

创建一个SpringBoot Initialize项目，详情可以参考我之前博客：[SpringBoot系列之快速创建项目教程][SpringBoot]  
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port: 8083
    spring:
      application:
        name: feign-service-consumer
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/
        healthcheck:
          enabled: false
      instance:
        status-page-url-path: http://localhost:8761/actuator/info
        health-check-url-path: http://localhost:8761/actuator//health
        prefer-ip-address: true
        instance-id: feign-service-consumer8083

`@FeignClient`指定服务名称，`@RequestMapping`指定要调用的接口

package com.example.springcloud.client.service;
    
    import com.example.springcloud.client.bean.User;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.stereotype.Service;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    
    /** * <pre> * UserService * </pre> * * <pre> * @author mazq * 修改记录 * 修改后版本: 修改人： 修改日期: 2020/07/28 13:09 修改内容: * </pre> */
    @FeignClient(value = "EUREKA-SERVICE-PROVIDER")
    @Service
    public interface UserService { 
        @RequestMapping(value = "/api/users/{username}",method = RequestMethod.GET)
        User findGithubUser(@PathVariable("username")String username);
    
    }

加上`@EnableEurekaClient`，`@EnableFeignClients`，写个接口进行测试

package com.example.springcloud.client;
    
    import com.example.springcloud.client.bean.User;
    import com.example.springcloud.client.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    import org.springframework.scheduling.annotation.Async;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RestController;
    
    @SpringBootApplication
    @EnableEurekaClient
    @EnableFeignClients
    @RestController
    public class SpringcloudFeignClientApplication { 
    
        @Autowired
        UserService userService;
    
        public static void main(String[] args) { 
            SpringApplication.run(SpringcloudFeignClientApplication.class, args);
        }
    
        @GetMapping("/findUser/{username}")
        public User index(@PathVariable("username")String username){ 
            return userService.findGithubUser(username);
        }
    }

要运行eureka服务端，eureka服务提供者，代码请参考[上一章博客][Link 1]

补充：IDEA中多实例运行方法

step1：如图，不要加上勾选  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0MjczOTE_size_16_color_FFFFFF_t_70 3]

step2：指定不同的server端口和实例id，如图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0MjczOTE_size_16_color_FFFFFF_t_70 4]

服务注册，可以看到两个实例  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0MjczOTE_size_16_color_FFFFFF_t_70 5]  
ok，启动eureka server（服务注册中心），eureka服务提供者端，和feign服务消费者端  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0MjczOTE_size_16_color_FFFFFF_t_70 6]  
[http://localhost:8083/findUser/mojombo][http_localhost_8083_findUser_mojombo]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0MjczOTE_size_16_color_FFFFFF_t_70 7]  
附录：

ok，本博客参考官方教程进行实践，仅仅作为入门的学习参考资料，详情可以参考Spring Cloud官方文档[https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.0.RELEASE/reference/html/][https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.0.RELEASE_reference_html]

代码例子下载：[code download][]

优质学习资料参考：

*  方志鹏大佬系列Spring Cloud博客：[https://www.fangzhipeng.com/spring-cloud.html][https_www.fangzhipeng.com_spring-cloud.html]
 *  使用Spring Cloud与Docker实战微服务：[https://eacdy.gitbooks.io/spring-cloud-book/content/][https_eacdy.gitbooks.io_spring-cloud-book_content]
 *  程序员DD大佬系列Spring Cloud博客：[http://blog.didispace.com/spring-cloud-learning/][http_blog.didispace.com_spring-cloud-learning]

[Link 1]: https://smilenicky.blog.csdn.net/article/details/107567035
[SpringBoot]: https://blog.csdn.net/u014427391/article/details/102870300
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[http_localhost_8083_findUser_mojombo]: http://localhost:8083/findUser/mojombo
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0MjczOTE_size_16_color_FFFFFF_t_70 7]: /images/20210813/e90b8e47b24340029d449c372650f980.png
[https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.0.RELEASE_reference_html]: https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.0.RELEASE/reference/html/
[code download]: https://github.com/u014427391/springCloudExamples/tree/master/springcloud-eureka
[https_www.fangzhipeng.com_spring-cloud.html]: https://www.fangzhipeng.com/spring-cloud.html
[https_eacdy.gitbooks.io_spring-cloud-book_content]: https://eacdy.gitbooks.io/spring-cloud-book/content/
[http_blog.didispace.com_spring-cloud-learning]: http://blog.didispace.com/spring-cloud-learning/