Feign

墨蓝 2023-07-21 15:28 12阅读 0赞

>  *  GitHub：[https://github.com/openfeign/feign][https_github.com_openfeign_feign]
>  *  [https://docs.spring.io/spring-cloud-openfeign/docs/2.2.4.RELEASE/reference/html/][https_docs.spring.io_spring-cloud-openfeign_docs_2.2.4.RELEASE_reference_html]

>  *  Ribbon：[https://yuanyu.blog.csdn.net/article/details/105280587][https_yuanyu.blog.csdn.net_article_details_105280587] 
>  *  Nacos：[https://blog.csdn.net/qq\_40794973/article/details/104593366][https_blog.csdn.net_qq_40794973_article_details_104593366]

Feign是Netflix开源的声明式HTTP客户端

--------------------

# 2 hello world #

## 2.1 加依赖 ##

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

## 2.2 加注解 ##

> 在SpringBoot的启动类上加@EnableFeignClients注解，如果SpringBoot无法扫描到（当前包及其子包）Feign的接口需要指定basePackages

@SpringBootApplication
    //Feign定义的接口没有在当前项目；是通过依赖引入的接口；需要指定扫描路径
    @EnableFeignClients(basePackages = {"com.nobug.user.client"})
    public class ClientApplication {
        public static void main(String[] args) {
            new SpringApplicationBuilder(ClientApplication.class)
                    .web(WebApplicationType.SERVLET)
                    .run(args);
        }
    }

## 2.3 写配置 ##

无需配置文件

## 2.4 写接口 ##

@FeignClient(name = "user-center")
    public interface UserCenterFeignClient {
        /**
         * 添加用户
         */
        @PostMapping("/user/")
        UserDTO addUser(@SpringQueryMap UserDTO user);
        /**
         * 查找用户
         * http://user-center/user/{userName}
         */
        @GetMapping("/user/{userName}")
        UserDTO getUser(@PathVariable("userName") String userName);
        /**
         * 查找所有
         */
        @GetMapping("/user/")
        UserDTO allUser();
    }

--------------------

# 3 Feign的组成 #

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70][]

//feign.Client.Default#convertAndSend
    HttpURLConnection convertAndSend(Request request, Options options) throws IOException {
    	URL url = new URL(request.url());
    	//HttpURLConnection去发送请求 无连接池 无资源管理的概念
    	//性能不是很好
    	HttpURLConnection connection = this.getConnection(url);
    	if (connection instanceof HttpsURLConnection) {
    		HttpsURLConnection sslCon = (HttpsURLConnection)connection;
    		if (this.sslContextFactory != null) {
    			sslCon.setSSLSocketFactory(this.sslContextFactory);
    		}
    		if (this.hostnameVerifier != null) {
    			sslCon.setHostnameVerifier(this.hostnameVerifier);
    		}
    	}

//org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient
    public class LoadBalancerFeignClient implements Client {
        static final Options DEFAULT_OPTIONS = new Options();
        //用到了代理模式
        private final Client delegate; //默认：带有负载均衡的 Client.Default(null, null) 也会用URLConnection发送请求【后面的优化手段就是引入连接池这些】
    	
    //org.springframework.cloud.openfeign.ribbon.DefaultFeignLoadBalancedConfiguration
    @Configuration(proxyBeanMethods = false)
    class DefaultFeignLoadBalancedConfiguration {
    	@Bean
    	@ConditionalOnMissingBean
    	public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory, SpringClientFactory clientFactory) {
    		return new LoadBalancerFeignClient(new Client.Default(null, null), cachingFactory, clientFactory);
    	}
    }

--------------------

# 4 指定日志级别 #

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70 1][]

2020-04-07 09:40:03.482 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] <--- HTTP/1.1 200 (1788ms)
    2020-04-07 09:40:03.482 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] content-length: 17
    2020-04-07 09:40:03.482 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] content-type: text/plain;charset=UTF-8
    2020-04-07 09:40:03.482 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] date: Tue, 07 Apr 2020 01:40:03 GMT
    2020-04-07 09:40:03.482 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] 
    2020-04-07 09:40:03.482 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] 192.168.56.1:8764
    2020-04-07 09:40:03.483 DEBUG 4060 --- [nio-9761-exec-1] c.n.u.client.UserCenterInfoFeignClient   : [UserCenterInfoFeignClient#info] <--- END HTTP (17-byte body)

## 4.1 细粒度配置  ##

### 4.1.1 Java代码配置  ###

@FeignClient(name="user-center", configuration = UserCenterFeignConfiguration.class)
    public interface UserCenterInfoFeignClient {
        /**
         * 返回服务器的ip和端口信息
         */
        @GetMapping("/user/info")
        String info();
    }

/**
     * 自定义日志级别
     * 这个类别加@Configuration注解了，否则必须挪到@ComponentScan能扫描到的包以外，不然就成为全局配置了【父子上下文重复扫描】
     */
    public class UserCenterFeignConfiguration {
        @Bean
        public Logger.Level level(){
            //打印所有请求的细节
            return Logger.Level.FULL;
        }
    }

logging:
      level:
        com.nobug.user.client.UserCenterInfoFeignClient: debug

### 4.1.2 配置文件 ###

feign.client.config.<feignName>.loggerLevel: full

feign:
      client:
        config:
          user-center:
            loggerLevel: full

## 4.2 全局配置 ##

### 4.2.1 Java代码配置 ###

> 方式一：让父子上下文ComponentScan重叠（强烈不建议使用）
> 
> 方式二【唯一正确的途径】: @EnableFeignClients(defaultConfiguration=xxx.class)

@EnableFeignClients(basePackages = {"com.nobug.user.client"}, defaultConfiguration = GlobalFeignConfiguration.class) //全局配置
    @SpringBootApplication
    public class ClientApplication {
        public static void main(String[] args) {
            new SpringApplicationBuilder(ClientApplication.class)
                    .web(WebApplicationType.SERVLET)
                    .run(args);
        }
    }

public class GlobalFeignConfiguration {
        @Bean
        public Logger.Level level(){
            //打印所有请求的细节
            return Logger.Level.FULL;
        }
    }

### 4.2.2 配置文件 ###

> 将想要调用的微服务名称换成default就可以实现属性方式的全局配置

feign.client.config.<feignName>.loggerLevel: full

feign:
      client:
        config:
          default:
            loggerLevel: full

--------------------

# 5 支持的配置项 #

## 5.1 代码方式 ##

<table> 
 <thead> 
  <tr> 
   <th style="width:311px;">配置项</th> 
   <th style="width:601px;">作用</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="width:311px;">Feign.Builder</td> 
   <td style="width:601px;">Feign的入口</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Client</td> 
   <td style="width:601px;">Feign底层用什么去请求</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Contract</td> 
   <td style="width:601px;">契约，注解支持</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Encoder</td> 
   <td style="width:601px;">编码器，用于将对象转换成HTTP请求消息体</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Decoder</td> 
   <td style="width:601px;">解码器，将响应消息体转换成对象</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Logger</td> 
   <td style="width:601px;">日志管理器</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Logger.Level</td> 
   <td style="width:601px;">指定日志级别</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Retryer</td> 
   <td style="width:601px;">指定重试策略</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">ErrorDecoder</td> 
   <td style="width:601px;">指定错误解码器</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Request.Options</td> 
   <td style="width:601px;">超时时间</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">Collection&lt;RequestInterceptor&gt;</td> 
   <td style="width:601px;">拦截器</td> 
  </tr> 
  <tr> 
   <td style="width:311px;">SetterFactory</td> 
   <td style="width:601px;">用于设置Hystrix的配置属性，Feign整合Hystrix才会用</td> 
  </tr> 
 </tbody> 
</table>

## 5.2 属性方式 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70 2][]

--------------------

# 6 配置最佳实践总结 #

## 6.1 Ribbon配置 vs Feign配置 ##

## ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70 3][]   6.2 Feign代码方式 vs 属性方式 ##

<table> 
 <thead> 
  <tr> 
   <th style="width:143px;">配置方式</th> 
   <th style="width:290px;">优点</th> 
   <th style="width:457px;">缺点</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="width:143px;">代码配置</td> 
   <td style="width:290px;">基于代码，更加灵活</td> 
   <td style="width:457px;">如果Feign的配置类加了Configuration注解，需注意父子上下文；线上修改得重新打包、发布</td> 
  </tr> 
  <tr> 
   <td style="width:143px;">属性配置</td> 
   <td style="width:290px;"> <p>易上手；配置更加直观；线上修改无需重新打包、发布；<span style="color:#f33b45;">优先级更高</span></p> <p>【全局代码 &lt; 全局属性 &lt; 细粒度代码 &lt; 细粒度属性】</p> </td> 
   <td style="width:457px;">极端场景下没有代码配置方式灵活</td> 
  </tr> 
 </tbody> 
</table>

## 6.3 最佳实践 ##

>  *  尽量使用属性配置,属性方式实现不了的情况下再考虑用代码配置
>  *  在同一个微服务内尽量保持单一性，比如统一使用属性配置，不要两种方式混用，增加定位代码的复杂性

--------------------

# 7 Feign的继承 #

>  *  官方观点：不建议使用
>  *  业界观点：很多公司使用

> [https://cloud.spring.io/spring-cloud-static/Greenwich.SR2/single/spring-cloud.html\#spring-cloud-feign-inheritance][https_cloud.spring.io_spring-cloud-static_Greenwich.SR2_single_spring-cloud.html_spring-cloud-feign-inheritance]
> 
> It is generally not advisable to share an interface between a server and a client. It introduces tight coupling, and also actually doesn’t work with Spring MVC in its current form (method parameter mapping is not inherited).

--------------------

# 8 多参数请求构造 #

> [http://www.imooc.com/article/289000][http_www.imooc.com_article_289000]

@FeignClient(name = "user-center")
    public interface UserCenterFeignClient {
        /**
         * ~/user/q?username=1&password=12346
         */
        @GetMapping("/user/q")
        UserDTO query(@SpringQueryMap UserDTO user);
    }

> 如果有两个以上的FeignClient接口name相同会报错

spring:
      main:
        allow-bean-definition-overriding: true

--------------------

# 9 Feign脱离Ribbon使用 #

/**
     * 脱离ribbon的使用
     * name必须有，随便取
     */
    @FeignClient(name = "baidu", url = "www.baidu.com")
    public interface BaiduFeignClient {
        @GetMapping("")
        String getIndexHtml();
    }

--------------------

# 10 RestTemplate vs Feign #

<table> 
 <thead> 
  <tr> 
   <th style="width:237px;">角度</th> 
   <th style="width:269px;">RestTemplate</th> 
   <th style="width:393px;">Feign</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="width:237px;">可读性、可维护性</td> 
   <td style="width:269px;">一般</td> 
   <td style="width:393px;">极佳</td> 
  </tr> 
  <tr> 
   <td style="width:237px;">开发体验</td> 
   <td style="width:269px;">欠佳</td> 
   <td style="width:393px;">极佳</td> 
  </tr> 
  <tr> 
   <td style="width:237px;">性能</td> 
   <td style="width:269px;">很好</td> 
   <td style="width:393px;">中等&nbsp; (RestTemplate的50%左右)</td> 
  </tr> 
  <tr> 
   <td style="width:237px;">灵活性</td> 
   <td style="width:269px;">极佳</td> 
   <td style="width:393px;">中等 (内置功能可满足绝大多数需求)</td> 
  </tr> 
 </tbody> 
</table>

> 如何选择?
> 
> 原则：尽量用Feign，杜绝使用RestTemplate

--------------------

# 11 Feign性能优化 #

## 11.1 连接池【提升15%左右】 ##

> 加依赖

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

> 写配置

feign:
      httpclient:
        max-connections: 200           # feign的最大连接数
        max-connections-per-route: 50  # feign单个路径最大的连接数
        enabled: true                  # 让feign使用apache httpclient发送请求，而不是默认的urlConnection

>  okhttp

<dependency>
        <groupId>io.github.openfeign</groupId>
        <artifactId>feign-okhttp</artifactId>
        <version>10.9</version>
    </dependency>

feign:
      httpclient:
        max-connections: 200
        max-connections-per-route: 50
      okhttp:
        enabled: true

## 11.2 日志级别 ##

--------------------

# 12 常见问题 #

> [http://www.imooc.com/article/289005][http_www.imooc.com_article_289005]

> [https://keepgoon.blog.csdn.net/article/details/101297264][https_keepgoon.blog.csdn.net_article_details_101297264]

[https_github.com_openfeign_feign]: https://github.com/openfeign/feign
[https_docs.spring.io_spring-cloud-openfeign_docs_2.2.4.RELEASE_reference_html]: https://docs.spring.io/spring-cloud-openfeign/docs/2.2.4.RELEASE/reference/html/
[https_yuanyu.blog.csdn.net_article_details_105280587]: https://yuanyu.blog.csdn.net/article/details/105280587
[https_blog.csdn.net_qq_40794973_article_details_104593366]: https://blog.csdn.net/qq_40794973/article/details/104593366
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70 1]: /images/20230528/459beb97a63b423584298695755fb251.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70 2]: /images/20230528/c6afd6beb1524a219aa8cbaace099b81.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNzk0OTcz_size_16_color_FFFFFF_t_70 3]: /images/20230528/c377398c141b450c93f3641fabc326e4.png
[https_cloud.spring.io_spring-cloud-static_Greenwich.SR2_single_spring-cloud.html_spring-cloud-feign-inheritance]: https://cloud.spring.io/spring-cloud-static/Greenwich.SR2/single/spring-cloud.html#spring-cloud-feign-inheritance
[http_www.imooc.com_article_289000]: http://www.imooc.com/article/289000
[http_www.imooc.com_article_289005]: http://www.imooc.com/article/289005
[https_keepgoon.blog.csdn.net_article_details_101297264]: https://keepgoon.blog.csdn.net/article/details/101297264