Spring Cloud之feign调用

小灰灰 2020-11-28 15:42 661阅读 0赞

# Spring Cloud之feign调用 #

## feign简介 ##

Feign是一个声明式的伪Http客户端，它使得写Http客户端变得更简单。使用Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

## 准备工作 ##

### 服务注册中心 ###

先创建一个服务注册中心，IDEA中先在父项目中new一个module：  
![这里写图片描述][SouthEast]  
然后next：  
![这里写图片描述][SouthEast 1]  
next,然后选择Cloud Discovery，选择Eureka Server，再next，finish。  
![这里写图片描述][SouthEast 2]

然后再在src中的EurekaServerApplication中加上@EnableEurekaServer注解，表明它是一个注册中心  
![这里写图片描述][SouthEast 3]

最后在resources目录下的application.properties中写入：

server.port=8761
    eureka.instance.hostname=localhost
    eureka.client.register-with-eureka=false
    eureka.client.fetch-registry=false
    eureka.client.service-url.defaultZone=http://localhost:${server.port}/eureka/

之后可以启动注册中心，浏览器输入localhost:8761,可以看到暂时是没有注册的  
![这里写图片描述][SouthEast 4]

### 创建一个服务提供者 ###

新建一个module，创建一个服务提供者eureka-client，过程和上面创建注册中心可以是一样的。  
然后在EurekaClientApplication中：

package com.springcloud.eurekaclient;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    
    @SpringBootApplication
    @EnableEurekaClient
    public class EurekaClientApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(EurekaClientApplication.class, args);
        }
    }

在resources目录下的application.yml(后缀改名为yml文件，这种写法感觉更好用)

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/
    server:
      port: 8762
    
    spring:
      application:
        name: service-A

这时可以新建controller层和service层，写几个服务方法：  
![这里写图片描述][SouthEast 5]  
比如 serviceClientController:

package com.springcloud.eurekaclient.Controller;
    
    import com.springcloud.eurekaclient.Service.IFeignSevice;
    import com.springcloud.eurekaclient.dto.User;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.web.bind.annotation.*;
    
    /** * Copyright Shanghai Hand Co. Ltd. * * @author liguo.wang@hand-china.com * @date 2018/1/29 14:24 * @version: 1.0 * @description */
    @RestController
    public class serviceClientController { 
    
        @Value("${server.port}")
        private String port;
    
        @Autowired
        private IFeignSevice feignSevice;
    
        @RequestMapping(value = "/",method = RequestMethod.GET)
        public String getServiceClientPort(){
    
            return "我是服务提供者的第一个方法" + feignSevice.getMsg(port);
        }
    
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        public String getServiceClientPort2(String name){
            return "我是服务提供者的第二个方法," + name + feignSevice.getMsg(port);
        }
    
        @RequestMapping(value = "/helloworld",method = RequestMethod.POST)
        public String getService(@RequestBody User user){
            return "我是服务提供者的第三个方法," + feignSevice.getMsg2(port,user);
        }
    }

service实现类：

package com.springcloud.eurekaclient.Service.FeignServiceImpl;
    
    import com.springcloud.eurekaclient.Service.IFeignSevice;
    import com.springcloud.eurekaclient.dto.User;
    import org.springframework.stereotype.Service;
    
    /** * Copyright Shanghai Hand Co. Ltd. * * @author liguo.wang@hand-china.com * @date 2018/1/29 19:39 * @version: 1.0 * @description */
    @Service
    public class FeignServiceImpl implements IFeignSevice { 
        @Override
        public String getMsg(String port) {
            return " 我的端口号是："+port;
        }
    
        @Override
        public String getMsg2(String port, User user) {
            String msg = " 我的端口号是："+port+" 姓名"+user.getUserName()+" 身高"+user.getHeight()+" 年龄"+user.getAge();
            return msg;
        }
    }

然后启动项目，浏览器访问第一个方法，因为其他两个方法需要参数，然后我们会在后面使用feign来调用这两个方法。  
可以看到，服务注册到注册中心了  
![这里写图片描述][SouthEast 6]  
然后访问浏览器地址：  
![这里写图片描述][SouthEast 7]

## 创建一个feign服务 ##

新建模块的过程和前面的类似，只是pom文件引入的依赖不一样，如图：  
![这里写图片描述][SouthEast 8]  
然后 ServiceFeignApplication：

package com.springcloud.servicefeign;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.feign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients
    public class ServiceFeignApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(ServiceFeignApplication.class, args);
        }
    }

application.yml:

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/
    server:
      port: 8765
    spring:
      application:
        name: service-feign

然后在feign服务里面创建controller层和service层：  
![这里写图片描述][SouthEast 9]  
frignController:

package com.springcloud.servicefeign.Controller;
    
    import com.springcloud.servicefeign.Service.IFeignService;
    import com.springcloud.servicefeign.dto.User;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    /** * Copyright Shanghai Hand Co. Ltd. * * @author liguo.wang@hand-china.com * @date 2018/1/29 17:09 * @version: 1.0 * @description */
    @RestController
    public class frignController { 
    
        @Autowired
        private IFeignService feignService;
    
        @RequestMapping(value = "/",method = RequestMethod.GET)
        public String getMsg(){
            return feignService.getMsg();
        }
    
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        public String getServiceClientPort(){
            String name = "我是帅哥";
            return feignService.getServiceClientPort(name);
        }
    
        @RequestMapping(value = "/hello")
        public String getServiceClientPort2(){
            User user = new User().setUserName("wlg").setHeight(174).setAge(18);
            return feignService.getServiceClientPort2(user);
        }
    }

IFeignService:

package com.springcloud.servicefeign.Service;
    
    import com.springcloud.servicefeign.dto.User;
    import org.springframework.cloud.netflix.feign.FeignClient;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    
    /** * Copyright Shanghai Hand Co. Ltd. * * @author liguo.wang@hand-china.com * @date 2018/1/29 17:22 * @version: 1.0 * @description */
    @FeignClient(value = "service-A")
    public interface IFeignService {
    
        @RequestMapping(value = "/")
        String getMsg();
    
        @RequestMapping(value = "/hi")
        String getServiceClientPort(@RequestParam("name") String name);
    
        @RequestMapping(value = "/helloworld")
        String getServiceClientPort2(@RequestBody User user);
    }

通过注解@FeignClient(value = “service-A”)找到服务提供者service-A，再通过@RequestMapping(value = “”)找到要调用的方法，  
这里的例子举了调用GET方法和POST方法。feign调用的一方记得加上注解，比如说get请求的@RequestParam注解，@PathVariable注解等等，  
post请求记得加上@RequestBody注解等等。被feign调用的一方由于是controller层，所以带参数的话这些注解按道理是有的，  
但被调用的一方的controller的某个GET请求接口如果仅仅只是用来被feign调用，我发现在这边的参数不写注解也是行的。比如：  
![这里写图片描述][SouthEast 10]  
启动项目，看注册中心：  
![这里写图片描述][SouthEast 11]  
浏览器再分别访问localhost:8765的三个接口：  
![这里写图片描述][SouthEast 12]  
![这里写图片描述][SouthEast 13]  
![这里写图片描述][SouthEast 14]

[SouthEast]: /images/1606578128315.png
[SouthEast 1]: /images/1606578102545.png
[SouthEast 2]: /images/1606578081792.png
[SouthEast 3]: /images/1606578061015.png
[SouthEast 4]: /images/1606578038942.png
[SouthEast 5]: /images/1606578014215.png
[SouthEast 6]: /images/1606577990365.png
[SouthEast 7]: /images/1606577966823.png
[SouthEast 8]: /images/1606577945200.png
[SouthEast 9]: /images/1606577921942.png
[SouthEast 10]: /images/1606577898502.png
[SouthEast 11]: /images/1606577876718.png
[SouthEast 12]: /images/1606577660606.png
[SouthEast 13]: /images/1606577638613.png
[SouthEast 14]: /images/1606577611723.png