un8.2:springcloud——使用feign实现微服务之间的调用。

红太狼 2023-10-11 18:06 22阅读 0赞

Feign是Netflix开发的声明式、模板化的HTTP客户端， Feign可以帮助我们更快捷、优雅地实现微服务之间的调用。  
一、Feign的优点是什么？

1.feign采用的是基于接口的注解；

2.feign整合了ribbon，具有负载均衡的能力；

3.整合了Hystrix，具有熔断的能力。  
二、项目编码

服务消费者content-center（内容中心微服务）向服务提供者user-center（用户中心微服务）发送请求，获取用户的微信昵称，我们通过Feign来实现该需求。

请求路径：http://localhost:8082/user/1

响应的json数据：

User u1 = new User(1, "小峰", "bigBadEgg", "https://sdjklsjfklsdfjklsf.jpg");
    User u2 = new User(2, "小坏蛋", "lttleBadEgg", "https://sdjklsjfklsdfjklsf.jpg");

2.1、在pom.xml中添加依赖

<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>

2.2、在BootApplication中添加@EnableFeignClients注解

package com.example.content_center;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableFeignClients
    public class ContentCenterApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(ContentCenterApplication.class, args);
        }
    
    }

2.3、新建FeignClient实现Feign远程请求

package com.example.content_center.feignclient;
    
    import com.example.content_center.entity.User;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    
    //Feign访问微服务的名称
    @FeignClient(name = "user-center")
    public interface UserCenterFeignClient {
        /**
         * Feign会自动构建URL为http://user-center/user/get_user?id=xxx
         *
         * @param id
         * @return
         */
        @GetMapping("/user/get_user")
        User findById(@RequestParam int id);
    }

2.4、新建测试Controller

package com.example.content_center.controller;
    
    import com.example.content_center.entity.User;
    import com.example.content_center.feignclient.UserCenterFeignClient;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    @RequestMapping("/content")
    public class ContentController {
        @Autowired
        private UserCenterFeignClient feignClient;
        @GetMapping("/test")
        public User test(){
            //去user-center微服务中获取童用户信息
            return feignClient.findById(1);
        }
    }

2.5、测试效果

访问UserController可以通过feign顺利调用到user-center中的方法

[http://localhost:8070/user/get\_user?id=1][http_localhost_8070_user_get_user_id_1]

![0fd9c8bf2de542b784dbb46f5bee193e.png][]  
三、Feign自定义日志级别

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>级别</td> 
   <td>打印内容</td> 
  </tr> 
  <tr> 
   <td>NONE（默认值）</td> 
   <td>不记录任何日志</td> 
  </tr> 
  <tr> 
   <td>BASIC</td> 
   <td>仅记录请求方法、URL、请求状态码以及执行时间</td> 
  </tr> 
  <tr> 
   <td>HEADERS</td> 
   <td>BASIC级别的基础之上，记录请求和响应的header</td> 
  </tr> 
  <tr> 
   <td>FULL</td> 
   <td>记录请求和响应的header、body和元数据</td> 
  </tr> 
 </tbody> 
</table>

1、在application.yml添加属性，在application.yml中结合log添加属性

#设置日志输出级别
        logging:
          level:
            com.itmuch.contentcenter.feignclient.UserCenterFeignClient: debug
        feign:
          client:
            config:
              #想要调用的微服务的名称
              user-center:
                loggerLevel: full

2、测试效果

![80f31b1505a4413382d2774b0ae1df76.png][]

四、Feign支持的配置项

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>配置项&nbsp;</td> 
   <td>&nbsp;作用</td> 
  </tr> 
  <tr> 
   <td>Logger.Level</td> 
   <td>&nbsp;指定日志级别</td> 
  </tr> 
  <tr> 
   <td>Retryer</td> 
   <td>指定重试策略</td> 
  </tr> 
  <tr> 
   <td>ErrorDecoder&nbsp;</td> 
   <td>指定错误解码器</td> 
  </tr> 
  <tr> 
   <td>Request.Options</td> 
   <td>超时时间</td> 
  </tr> 
  <tr> 
   <td>Collection&lt;RequestInterceptor&gt;</td> 
   <td>&nbsp; &nbsp;拦截器</td> 
  </tr> 
  <tr> 
   <td>SetterFactory</td> 
   <td>&nbsp;用于设置Hystrix的配置属性，当Feign整合Hystrix时才会使用</td> 
  </tr> 
 </tbody> 
</table>

application.yml配置参考

![63c0e30dccd64774a1734ec8af8b20fa.png][]

五、多参数请求

1、多参数可以使用@SpringQueryMap注解实现

package com.itmuch.contentcenter.feignclient;
         
        import com.itmuch.contentcenter.domain.dto.user.UserDTO;
        import org.springframework.cloud.openfeign.FeignClient;
        import org.springframework.cloud.openfeign.SpringQueryMap;
        import org.springframework.web.bind.annotation.GetMapping;
         
        @FeignClient(name = "user-center")
        public interface TestUserCenterFeignClient {
            @GetMapping("/q")
            UserDTO query(@SpringQueryMap UserDTO userDTO);
        }

注意，在开发中可能会出现多个Feign接口访问同一个微服务的情况，解决方法：

2、在application.yml中添加属性配置

spring:
          #解决Feign多个Client接口指向同一个微服务出现异常的问题
          main:
            allow-bean-definition-overriding: true

六、脱离Nacos单独使用Feign  
1、新建FeignClient，请求user-center

2、在测试Controller中调用FeignClient方法

3、测试效果,网址：[http://localhost:8060/content/test][http_localhost_8060_content_test]

![53f0d10d08574ae395f2e5f29dac1ba2.png][]

七、RestTemplate和Feign对比

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>角度</td> 
   <td>&nbsp;RestTemplate&nbsp;</td> 
   <td>Feign</td> 
  </tr> 
  <tr> 
   <td>可读性、可维护性</td> 
   <td>&nbsp;一般</td> 
   <td>极佳</td> 
  </tr> 
  <tr> 
   <td>开发体验&nbsp;</td> 
   <td>欠佳</td> 
   <td>极佳</td> 
  </tr> 
  <tr> 
   <td>性能&nbsp;</td> 
   <td>很好</td> 
   <td>&nbsp;中等（RestTemplate的50%左右，但是可以使用连接池将性能提升15%所有）</td> 
  </tr> 
  <tr> 
   <td>灵活性</td> 
   <td>&nbsp;极佳</td> 
   <td>&nbsp;中等（内置功能可以满足绝大多数需求）</td> 
  </tr> 
 </tbody> 
</table>

八、Feign的性能优化  
1、使用连接池提升15%性能

pom.xml中添加依赖

<dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>

application.yml中添加属性配置连接池

feign:
          httpclient:
            #让feign使用Apache httpclient做请求，而不是默认的urlconnection
            enabled: true
            #feign的最大连接数
            max-connections: 200
            #feign单个路径的最大连接数
            max-connections-per-route: 50

2、将日志的级别设置为basic，不要使用full

feign:
          client:
            config:
              #想要调用的微服务的名称或全局配置
              default:
                loggerLevel: basic

九、Feign的常见问题总结

参考：https://www.imooc.com/article/289005  
十、pom.xml及源代码下载

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.5.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>com.example</groupId>
        <artifactId>user_center</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>user_center</name>
        <description>user_center</description>
        <properties>
            <java.version>1.8</java.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <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-alibaba-nacos-discovery</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.12</version>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
            <dependency>
                <groupId>io.github.openfeign</groupId>
                <artifactId>feign-httpclient</artifactId>
            </dependency>
        </dependencies>
        <dependencyManagement>
            <dependencies>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Greenwich.SR1</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>0.9.0.RELEASE</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    </project>

如此，我们便用feign实现微服务之间的调动，快行动起来吧。

[http_localhost_8070_user_get_user_id_1]: http://localhost:8070/user/get_user?id=1
[0fd9c8bf2de542b784dbb46f5bee193e.png]: https://img-blog.csdnimg.cn/0fd9c8bf2de542b784dbb46f5bee193e.png
[80f31b1505a4413382d2774b0ae1df76.png]: https://img-blog.csdnimg.cn/80f31b1505a4413382d2774b0ae1df76.png
[63c0e30dccd64774a1734ec8af8b20fa.png]: https://img-blog.csdnimg.cn/63c0e30dccd64774a1734ec8af8b20fa.png
[http_localhost_8060_content_test]: http://localhost:8060/content/test
[53f0d10d08574ae395f2e5f29dac1ba2.png]: https://img-blog.csdnimg.cn/53f0d10d08574ae395f2e5f29dac1ba2.png