【Spring Cloud 基础设施搭建系列】Spring Cloud Demo项目使用Feign实现声明式REST调用

Dear 丶 2024-04-19 08:09 9阅读 0赞

### 文章目录 ###

*   *  Feign简介
     *  微服务整合Feign
     *  参考
     *  源代码

## Feign简介 ##

Feign是Netflix开发的声明式、模板化的HTTP客户端，其灵感来自Retrofit、JAXRS-2.0以及WebSocket。Feign可帮助我们更加便捷、优雅地调用HTTPAPI。

在Spring Cloud中，使用Feign非常简单—创建一个接口，并在接口上添加一些注解，代码就完成了。Feign支持多种注解，例如Feign自带的注解或者JAX-RS注解等。  
Spring Cloud对Feign进行了增强，使Feign支持了Spring MVC注解，并整合了Ribbon和Eureka，从而让Feign的使用更加方便。

## 微服务整合Feign ##

1.  往cloud-service-member,cloud-service-order的pom文件中都加入Feign的依赖。

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

`<artifactId>spring-cloud-starter-feign</artifactId>`已经过期，推荐使用`<artifactId>spring-cloud-starter-openfeign</artifactId>`

1.  创建一个Feign接口，并添加@FeignClient注解。

*  cloud-service-member

package com.cc.cloud.member.feign;
    
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import java.util.List;
    
    @FeignClient("cloud-service-order")
    public interface OrderFeign { 
    
        @RequestMapping("/order/orders")
        List<String> getAllOrderList();
    }

修改Controller代码，让其调用Feign接口。

package com.cc.cloud.member.controller;
    
    import com.cc.cloud.member.feign.OrderFeign;
    import com.google.common.collect.Lists;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.http.HttpStatus;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseStatus;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    
    @RestController
    @RequestMapping("/member")
    public class MemberController { 
    
        private OrderFeign orderFeign;
    
    
        @Autowired
        public void setOrderFeign(OrderFeign orderFeign) { 
            this.orderFeign = orderFeign;
        }
    
        @RequestMapping("/orders")
        @ResponseStatus(HttpStatus.OK)
        public List<String> getOrderList() { 
            return orderFeign.getAllOrderList();
        }
    
        @RequestMapping("/members")
        @ResponseStatus(HttpStatus.OK)
        public List<String> getMemberList() { 
            List<String> memberList = Lists.newArrayList();
            memberList.add("member 1");
            memberList.add("member 2");
            memberList.add("member 3");
            return memberList;
        }
    
    }

*  cloud-service-order

package com.cc.cloud.order.feign;
    
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import java.util.List;
    
    @FeignClient("cloud-service-member")
    public interface MemberFeign { 
        @RequestMapping("/member/members")
        List<String> getAllMemberList();
    }

修改Controller代码，让其调用Feign接口。

package com.cc.cloud.order.controller;
    
    import com.cc.cloud.order.feign.MemberFeign;
    import com.google.common.collect.Lists;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.http.HttpStatus;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseStatus;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    @RestController
    @RequestMapping("/order")
    public class OrderController { 
    
        private MemberFeign memberFeign;
    
        @Autowired
        public void setMemberFeign(MemberFeign memberFeign) { 
            this.memberFeign = memberFeign;
        }
    
        @RequestMapping("/members")
        @ResponseStatus(HttpStatus.OK)
        public List<String> getMemberList() { 
            return memberFeign.getAllMemberList();
        }
    
    
        @GetMapping("/orders")
        @ResponseStatus(HttpStatus.OK)
        public List<String> getOrders() { 
            List<String> orders = Lists.newArrayList();
            orders.add("order 1");
            orders.add("order 2");
            return orders;
        }
    }

@FeignClient 注解中的cloud-service-member是一个任意的客户端名称，用于创建Ribbon负载均衡器。在本例中，由于使用了Eureka，所以Ribbon会把cloud-service-member解析成Eureka Server服务注册表中的服务。当然，如果不想使用Eureka，可使用service.ribbon.listofServers属性配置服务器列表.  
还可使用url属性指定请求的URL（URL可以是完整的URL或者主机名），例如  
@FeignClient（name =“cloud-service-member”，url=“http://localhost:8762”）。

1.  修改启动类，为其添加@EnableFeignClients注解，如下：

package com.cc.cloud.member;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableEurekaClient
    @EnableFeignClients
    public class MemberApp { 
        public static void main(String[] args) { 
            SpringApplication.run(MemberApp.class, args);
        }
    }

package com.cc.cloud.order;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableEurekaClient
    @EnableFeignClients
    public class OrderApp { 
        public static void main(String[] args) { 
            SpringApplication.run(OrderApp.class, args);
        }
    }

分别访问： http://localhost:8762/member/orders 和 http://localhost:8765/order/members

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70 1]

## 参考 ##

SpringCloud与Docker微服务架构实战-完整版.pdf

[【SpringCloud Greenwich版本】第三章：服务消费者（Feign）][SpringCloud Greenwich_Feign]

## 源代码 ##

[https://gitee.com/cckevincyh/spring-cloud-demo/tree/fegin][https_gitee.com_cckevincyh_spring-cloud-demo_tree_fegin]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/e2f924b52438485999d05b20c43435f4.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/a92648c7c6124ebe8ed7908b06a42511.png
[SpringCloud Greenwich_Feign]: https://blog.csdn.net/haobao528/article/details/85276379
[https_gitee.com_cckevincyh_spring-cloud-demo_tree_fegin]: https://gitee.com/cckevincyh/spring-cloud-demo/tree/fegin