SpringCloud Alibaba 微服务架构（四）- 服务调用之OpenFeign方式

迷南。 2023-05-22 14:25 35阅读 0赞

*  **OpenFeign属性配置列表文档：** [https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.2.RELEASE/reference/html/appendix.html][https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.2.RELEASE_reference_html_appendix.html]
 *  **OpenFeign官方教程文档：** [https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.2.RELEASE/reference/html/\#configuration-properties][https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.2.RELEASE_reference_html_configuration-properties]

## 一、前言 ##

`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。

Spring Cloud为Feign添加了Spring MVC的注解支持，并整合了Ribbon和Eureka来为使用Feign时提供负载均衡。使用@EnableFeignClients即可开启Feign。

**简而言之：**

*  `Feign`采用的是基于接口的注解
 *  `Feign`默认整合了`ribbon`，具有负载均衡的能力
 *  `Feign`默认整合了`Hystrix`，具有熔断的能力

## 二、初探Feign ##

微服务间的通讯是基于`HTTP`的，而`Feign`就是一个伪`HTTP`请求客户端，通过声明式的`Feign`客户端可以调用远程微服务，在实现远程微服务调用的过程中，多个实例存在的时候，`Ribbon`负载均衡器会默认的进行本地负载均衡，默认通过轮询机制进行微服务的调用，`Feign`默认则是集成了并且支持`Ribbon`负载均衡。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70]  
下面以订单服务`（Order）`调用商品服务`（Product）`为例，搭建环境使用`Feign`远程调用消费服务

## 三、父工程 ##

*  **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">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>org.example</groupId>
        <artifactId>springcloud-ribbon-hystrix</artifactId>
        <packaging>pom</packaging>
        <version>1.0-SNAPSHOT</version>
        <modules>
            <module>springcloud-product</module>
            <module>springcloud-order</module>
        </modules>
    
        <properties>
            <project.build.sourceEncoding> UTF-8 </project.build.sourceEncoding>
            <project.reporting.outputEncoding> UTF-8 </project.reporting.outputEncoding>
            <java.version> 1.8 </java.version>
        </properties>
    
        <dependencyManagement>
            <dependencies>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Greenwich.SR2</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
    
                
                <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-dependencies</artifactId>
                    <version>2.1.6.RELEASE</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
    
                
                <dependency>
                    <groupId>com.alibaba.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>2.1.1.RELEASE</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
    </project>

## 四、商品(Product)工程 ##

*  **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>springcloud-ribbon-hystrix</artifactId>
            <groupId>org.example</groupId>
            <version>1.0-SNAPSHOT</version>
        </parent>
        <modelVersion>4.0.0</modelVersion>
    
        <artifactId>springcloud-product</artifactId>
    
        <properties>
            <project.build.sourceEncoding> UTF-8 </project.build.sourceEncoding>
            <project.reporting.outputEncoding> UTF-8 </project.reporting.outputEncoding>
            <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-actuator</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba.nacos</groupId>
                <artifactId>nacos-client</artifactId>
                <version>1.2.0</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
            </dependency>
        </dependencies>
    
    </project>

*  **application.yml**

server:
      port: 8013
    
    spring:
      application:
        name: nacos-product
      cloud:
        nacos:
          discovery:
            #开启服务注册与发现功能
            enabled: true
            #服务注册与发现地址
            server-addr: 130.252.102.241:8848

*  **商品服务接口ProviderController**

package com.thinkingcao.product.controller;
    
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RestController;
    
    /** * @desc: 生产者-商品服务 * @author: cao_wencao * @date: 2020-04-29 19:48 */
    @RestController
    @Slf4j
    public class ProviderController { 
        @GetMapping(value = "/getProductInfo/{productId}")
        public String getProductInfo(@PathVariable("productId") String productId) { 
            log.info("请求进来啦");
            return "Hello Nacos Discovery " + productId;
        }
    }

*  **启动类ProductProviderApp**

package com.thinkingcao.product;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.cloud.client.SpringCloudApplication;
    
    /** * @desc: 商品服务-提供者 * @author: cao_wencao * @date: 2020-04-29 17:48 */
    @SpringCloudApplication
    public class ProductProviderApp { 
        public static void main(String[] args) { 
            SpringApplication.run(ProductProviderApp.class, args);
        }
    }

## 五、订单(Order)工程 ##

*  **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>springcloud-ribbon-hystrix</artifactId>
            <groupId>org.example</groupId>
            <version>1.0-SNAPSHOT</version>
        </parent>
        <modelVersion>4.0.0</modelVersion>
    
        <artifactId>springcloud-order</artifactId>
    
        <properties>
            <project.build.sourceEncoding> UTF-8 </project.build.sourceEncoding>
            <project.reporting.outputEncoding> UTF-8 </project.reporting.outputEncoding>
            <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-actuator</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
                <exclusions>
                    <exclusion>
                        <artifactId>nacos-client</artifactId>
                        <groupId>com.alibaba.nacos</groupId>
                    </exclusion>
                </exclusions>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba.nacos</groupId>
                <artifactId>nacos-client</artifactId>
                <version>1.2.0</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
            </dependency>
    
        </dependencies>
    </project>

*  **application.yml**

server:
      port: 8012
    
    spring:
      application:
        name: nacos-order
      cloud:
        nacos:
          discovery:
            enabled: true
            server-addr: 130.252.102.241:8848
            register-enabled: true

*  **定义`Feign`客户端`OrderFeign`**

> OrderFeign 中引入了Hystrix熔断器组件起到服务的保护降级作用，@FeignClient注解当中使用断路器支持的有两种方式fallback 和fallbackFactory

**关于Feign Hystrix Fallbacks：**  
**第一种：**`Hystrix`支持回退的概念：当它们的电路断开或出现错误时，将执行默认代码路径。要为给定`@FeignClient`集启用后备，该`fallback`属性应为实现后备的类名称。您还需要将实现声明为`Spring bean`。

package com.thinkingcao.order.feign;
    
    import com.thinkingcao.order.feign.callback.OrderFeignFallbackFactory;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    
    /** * @desc: 订单调用商品服务 * @author: cao_wencao * @date: 2020-04-29 20:19 */
    @FeignClient(name = "nacos-product",fallback = HystrixClientFallback.class)
    public interface OrderFeign { 
    
        @GetMapping(value = "/getProductInfo/{productId}")
        public String getProductInfo(@PathVariable("productId") String productId);
    
        static class HystrixClientFallback implements OrderFeign { 
            @Override
            public String getProductInfo(String productId) { 
                return "fallback; reason was: 服务忙，稍后重试" ;
            }
        }
    }

**第二种：** 如果需要访问引起后备触发器的原因，则可以使用`fallbackFactory inside`的属性`@FeignClient`。说白了就是如果你想知道服务调用为什么失败了，可以使用下面这种断路器方式。

package com.thinkingcao.order.feign;
    
    import com.thinkingcao.order.feign.callback.OrderFeignFallbackFactory;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    
    /** * @desc: 订单调用商品服务 * @author: cao_wencao * @date: 2020-04-29 20:19 */
    @FeignClient(name = "nacos-product",fallbackFactory = OrderFeignFallbackFactory.class)
    public interface OrderFeign { 
    
        @GetMapping(value = "/getProductInfo/{productId}")
        public String getProductInfo(@PathVariable("productId") String productId);
    
        @Component
        @Slf4j
        static class OrderFeignFallbackFactory implements FallbackFactory<OrderFeign> { 
          @Override
          public OrderFeign create(Throwable throwable) { 
             log.error("调用异常："+ throwable.toString());
             return new OrderFeign() { 
                @Override
                public String getProductInfo(String string) { 
                    return "开启断路-fallback; reason was: "+ throwable;
                }
            };
          }
    }

参考自官网： **[https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.2.RELEASE/reference/html/\#spring-cloud-feign-overriding-defaults][https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.2.RELEASE_reference_html_spring-cloud-feign-overriding-defaults]**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70 1]

*  **服务消费`OrderController`**

package com.thinkingcao.order.controller;
    
    import com.thinkingcao.order.feign.OrderFeign;
    import lombok.extern.slf4j.Slf4j;
    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;
    
    /** * @desc: 消费者-订单服务 * @author: cao_wencao * @date: 2020-04-29 19:50 */
    @RestController
    @Slf4j
    public class OrderController { 
        @Autowired(required = false)
        private OrderFeign orderFeign;
    
        @GetMapping("/getProduct/{productId}")
        public String getProduct(@PathVariable("productId") String id){ 
            String response = orderFeign.getProductInfo(id);
            log.info("调用服务结束： "+ response);
            return response;
        }
    }

*  **启动类OrderConsumerApp**

**`1.@SpringCloudApplication`**： 组合注解：

*  `@SpringBootApplication(启动SPringBoot程序)`、
 *  `@EnableDiscoveryClient(开启服务注册与发现)`、
 *  `@EnableCircuitBreaker(开启断路器)`

**`2.@EnableFeignClients`**： 开启`Feign`客户端

package com.thinkingcao.order;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.cloud.client.SpringCloudApplication;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    /** * @desc: 订单服务-消费者 * @author: cao_wencao * @date: 2020-04-29 17:50 */
    @SpringCloudApplication
    @EnableFeignClients
    public class OrderConsumerApp { 
        public static void main(String[] args) { 
            SpringApplication.run(OrderConsumerApp.class, args);
        }
    }

## 五、测试 ##

**地址：** [http://130.252.102.241:8012/getProduct/1010110][http_130.252.102.241_8012_getProduct_1010110]

**访问结果：** Hello Nacos Discovery 1010110  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70 2]

## 六、源码 ##

**[https://github.com/Thinkingcao/SpringCloudLearning/tree/master/springcloud-ribbon-hystrix][https_github.com_Thinkingcao_SpringCloudLearning_tree_master_springcloud-ribbon-hystrix]**

## 七、Spring Cloud Alibaba教程 ##

**1. 下一篇：** **《[Spring Cloud Alibaba教程五》- 使用Nacos实现分布式配置中心][Spring Cloud Alibaba_- _Nacos]**

**2. Nacos官方文档：** **[https://nacos.io/zh-cn/docs/what-is-nacos.html][https_nacos.io_zh-cn_docs_what-is-nacos.html]**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70 3]

[https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.2.RELEASE_reference_html_appendix.html]: https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.2.RELEASE/reference/html/appendix.html
[https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.2.RELEASE_reference_html_configuration-properties]: https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.2.RELEASE/reference/html/#configuration-properties
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70]: /images/20230521/23f1325600fb427c8e6fa2eeb97bbaa6.png
[https_cloud.spring.io_spring-cloud-static_spring-cloud-openfeign_2.2.2.RELEASE_reference_html_spring-cloud-feign-overriding-defaults]: https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.2.RELEASE/reference/html/#spring-cloud-feign-overriding-defaults
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70 1]: /images/20230521/b285a22e26ef4f4fb7340884f248e556.png
[http_130.252.102.241_8012_getProduct_1010110]: http://130.252.102.241:8012/getProduct/1010110
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70 2]: /images/20230521/71b507ee2f8c44d0a596bbc47d5b8e71.png
[https_github.com_Thinkingcao_SpringCloudLearning_tree_master_springcloud-ribbon-hystrix]: https://github.com/Thinkingcao/SpringCloudLearning/tree/master/springcloud-ribbon-hystrix
[Spring Cloud Alibaba_- _Nacos]: https://blog.csdn.net/Thinkingcao/article/details/105444692
[https_nacos.io_zh-cn_docs_what-is-nacos.html]: https://nacos.io/zh-cn/docs/what-is-nacos.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1RoaW5raW5nY2Fv_size_16_color_FFFFFF_t_70 3]: /images/20230521/2636767fb0a74a34be4f6398df12aff9.png