搭建springcloud的demo之Feign工程构建(六)

亦凉 2022-03-09 01:30 242阅读 0赞

## Feign的使用步骤 ##

**Feign只需要创建一个接口,然后在上面添加注解即可;**

**新建microservicecloud-consumer-dept-feign**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70]  
**microservicecloud-consumer-dept-feign工程的pom.xml,主要添加对feign的支持**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 1]  
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<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>
      <parent>
        <groupId>com.yt.springcloud</groupId>
        <artifactId>microservicecloud</artifactId>
        <version>0.0.1-SNAPSHOT</version>
      </parent>
      <artifactId>microservicecloud-consumer-dept-feign</artifactId>
      
      <dependencies>
      
      	<dependency>
      		<groupId>com.yt.springcloud</groupId> 
      		<artifactId>microservicecloud-api</artifactId>
      		<version>${project.version}</version>
      	</dependency>
      	
      	<dependency>
      		<groupId>org.springframework.boot</groupId>
      		<artifactId>spring-boot-starter-web</artifactId>
      	</dependency>
      	
      	 
      	<dependency>
      		<groupId>org.springframework</groupId>
      		<artifactId>springloaded</artifactId>
      	</dependency>
      	<dependency>
      		<groupId>org.springframework.boot</groupId>
      		<artifactId>spring-boot-devtools</artifactId>
      	</dependency>
      	
      		
      	<dependency>
      		<groupId>org.springframework.cloud</groupId>
      		<artifactId>spring-cloud-starter-eureka</artifactId>
      	</dependency>
      	<dependency>
      		<groupId>org.springframework.cloud</groupId>
      		<artifactId>spring-cloud-starter-ribbon</artifactId>
      	</dependency>
      	<dependency>
      		<groupId>org.springframework.cloud</groupId>
      		<artifactId>spring-cloud-starter-config</artifactId>
      	</dependency>
      	
      	
    	<dependency>
    		<groupId>org.springframework.cloud</groupId>
    		<artifactId>spring-cloud-starter-feign</artifactId>
    	</dependency>
    	
      </dependencies>
      
    </project>

**修改microservicecloud-api工程的pom.xml**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 3]

**microservicecloud-api工程添加一个DeptClientService接口并新增注解@FeignClient**  
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package com.yt.springcloud.service;
    
    import java.util.List;
    
    import org.springframework.cloud.netflix.feign.FeignClient;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    
    import com.yt.springcloud.entity.Dept;
    
    /**
     * 
     * @Description: 修改microservicecloud-api工程，根据已经有的DeptClientService接口
     * 一个实现了FallbackFactory接口的类DeptClientServiceFallbackFactory
     * @author zzyy
     * @date 2018年4月21日
     */
    @FeignClient(value = "MICROSERVICECLOUD-DEPT")//针对于更细粒化的控制,针对哪一个微服务进行面向接口的feign的
    //@FeignClient(value = "MICROSERVICECLOUD-DEPT",fallbackFactory=DeptClientServiceFallbackFactory.class)
    public interface DeptClientService
    {
    	@RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
    	public Dept get(@PathVariable("id") long id);
    
    	@RequestMapping(value = "/dept/list", method = RequestMethod.GET)
    	public List<Dept> list();
    
    	@RequestMapping(value = "/dept/add", method = RequestMethod.POST)
    	public boolean add(Dept dept);
    }

**对api公共项目工程maven clean–>maven install**  
**microservicecloud-consumer-dept-feign工程修改Controller,  
添加上一步新建的DeptClientService**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 5]

package com.yt.springcloud.controller;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.yt.springcloud.entity.Dept;
    import com.yt.springcloud.service.DeptClientService;
    
    @RestController
    public class DeptController_consumer {
    	
    	@Autowired
    	private DeptClientService service;
    
    	@RequestMapping(value = "/consumer/dept/get/{id}")
    	public Dept get(@PathVariable("id") Long id)
    	{
    		return this.service.get(id);
    	}
    
    	@RequestMapping(value = "/consumer/dept/list")
    	public List<Dept> list()
    	{
    		return this.service.list();
    	}
    
    	@RequestMapping(value = "/consumer/dept/add")
    	public Object add(Dept dept)
    	{
    		return this.service.add(dept);
    	}
    }

**microservicecloud-consumer-dept-feign工程修改主启动类**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 6]

package com.yt.springcloud;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.cloud.netflix.feign.EnableFeignClients;
    import org.springframework.context.annotation.ComponentScan;
    
    @SpringBootApplication
    @EnableEurekaClient
    @EnableFeignClients(basePackages= {"com.yt.springcloud"})
    @ComponentScan("com.yt.springcloud")
    public class DeptConsumer80_Feign_App {
    	
    	public static void main(String[] args) {
    		SpringApplication.run(DeptConsumer80_Feign_App.class, args);
    	}
    
    }

**测试**  
**先启动3个rureka项目工程,再驱动8001,8002,8003,和feign项目工程**  
**测试路径:[http://localhost/consumer/dept/list][http_localhost_consumer_dept_list]**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 7]

**如果控制台报了这个异常的话**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 8]  
**去feign项目工程的配置类里面加上一个方法**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 9]

package com.yt.springcloud.cfgbeans;
    
    import org.springframework.cloud.client.loadbalancer.LoadBalanced;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.client.RestTemplate;
    
    import com.fasterxml.jackson.databind.ObjectMapper;
    import com.fasterxml.jackson.databind.SerializationFeature;
    import com.netflix.loadbalancer.IRule;
    import com.netflix.loadbalancer.RandomRule;
    
    @Configuration//其实就是ApplicationContext.xml
    public class ConfigBean {
    	
    	/**
    	 * 注册一个objectMapper覆盖掉默认的,这样就不用在每个类上面使用@jsonIgnoreProperties
    	 * @return
    	 */
    	@Bean
    	public ObjectMapper objectMapper() {
    		return new ObjectMapper().disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
    	}
    	
    	
    	/**
    	 * RestTemplate提供了多种便捷访问远程Http服务的方法
    	 * 是一种简单便捷的访问restful服务模板类,是Spring提供的用于访问Rest服务的客户端模板工具集
    	 * @return
    	 */
    	@Bean
    	@LoadBalanced//ribbon是客户端的负载均衡工具,所以在rest去访问微服务的时候,自带负载均衡,这个注解是开启负载均衡的
    	public RestTemplate getRestTemplate() {
    		return new RestTemplate();
    	}
    	
    	/**
    	 * 自定义负载均衡算法(有7种负载均衡算法)
    	 * 有显示的声明算法,就覆盖默认的轮询算法
    	 * @return
    	 */
    	@Bean
    	public IRule myRule() {
    		
    		//return new RoundRobinRule();//轮询算法
    		return new RandomRule();//随机算法
    	}
    
    }

## Feign集成了Ribbon ##

**利用Ribbon维护了microservicecloud-Dept的服务列表信息,并且通过轮询实现了客户端的负载均衡,而与Ribbon不同的是,通过feign只需要定义服务绑定接口且以声明式的方法,优雅而简单的实现了服务调用**

**Feign通过接口的方法,调用Rest服务(之前是Ribbon+RestTemplate)**  
该请求发送给Eureka服务器([http://MICROSERVICECLOUD-DEPT/dept/list][http_MICROSERVICECLOUD-DEPT_dept_list]),通过Feign直接找到服务接口,由于在进行服务调用的时候融合了Ribbon技术,所以也支持负载均衡作用;

## 总结 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 10]  
翻译于尚硅谷周阳老师:[https://www.bilibili.com/video/av22613028?from=search&seid=11377756339718254280][https_www.bilibili.com_video_av22613028_from_search_seid_11377756339718254280]

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[http_localhost_consumer_dept_list]: http://localhost/consumer/dept/list
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 7]: /images/20220309/a636f83f323546ea9cbdb3f85f8cce29.png
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[http_MICROSERVICECLOUD-DEPT_dept_list]: http://MICROSERVICECLOUD-DEPT/dept/list
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 10]: /images/20220309/55a10ecbb68442c8886fbaaca53324de.png
[https_www.bilibili.com_video_av22613028_from_search_seid_11377756339718254280]: https://www.bilibili.com/video/av22613028?from=search&seid=11377756339718254280