SpringCloud - （三）服务消费者（feign）

深藏阁楼爱情的钟 2022-05-26 06:22 322阅读 0赞

## Feign ##

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。***

简而言之：

*  Feign 采用的是基于接口的注解
 *  Feign 整合了ribbon

## 准备工作 ##

启动项目

*  Ahut-Eureka-Server（注册中心）
 *  Ahut-Eureka-Client-One（AHUT-EUREKA-CLIENT服务一）
 *  Ahut-Eureka-Client-Two（AHUT-EUREKA-CLIENT服务二）

浏览器访问Eureka  
![这里写图片描述][70]

## 此时的项目架构 ##

![这里写图片描述][70 1]

## 创建服务消费者 ##

新创建一个项目Ahut-Service-Feign，和Ahut-Eureka-Client-One类似

右键，New>>Module>>Spring Init>>填写项目maven信息>>选择依赖>>填写项目名称

![这里写图片描述][70 2]

pom.xml文件如下

<?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>com.ahut</groupId>
        <artifactId>service-feign</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <name>service-feign</name>
        <description>service feign</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.12.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.version>
            <spring-cloud.version>Edgware.SR3</spring-cloud.version>
        </properties>
    
        <dependencies>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</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-feign</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    
    </project>

项目启动类  
加上@EnableFeignClients注解开启Feign的功能

package com.ahut;
    
    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;
    
    /** * @author cheng * @className: ServiceFeignApplication * @description: service feign * @dateTime 2018/4/26 16:36 */
    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients
    public class ServiceFeignApplication { 
    
        public static void main(String[] args) {
            SpringApplication.run(ServiceFeignApplication.class, args);
        }
    }

项目配置文件application.properties

# 配置服务器端口
    server.port=8930
    # spring项目名称
    spring.application.name=AHUT-SERVICE-FEIGN
    # 配置注册中心
    eureka.client.service-url.defaultZone=http://localhost:8900/eureka/

声明一个接口HelloService  
通过@ FeignClient（“服务名”），来指定调用哪个服务

package com.ahut.service;
    
    import org.springframework.cloud.netflix.feign.FeignClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    /** * @author cheng * @interfaceName: HelloService * @description: * @dateTime 2018/4/26 16:39 */
    @FeignClient(value = "AHUT-EUREKA-CLIENT")
    public interface HelloService { 
    
        @RequestMapping(value = "/v1/showPort")
        String showPort();
    
        /** * @description: 演示带参数 * @author cheng * @dateTime 2018/4/26 16:45 */
        //@GetMapping(value = "/demo")
        //void demo(@RequestParam(value = "name") String name);
    
    }

控制层HelloAction

package com.ahut.action;
    
    import com.ahut.service.HelloService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    /** * @author cheng * @className: HelloAction * @description: * @dateTime 2018/4/26 14:40 */
    @RestController
    @RequestMapping(value = "/v1")
    public class HelloAction { 
    
        @Autowired
        private HelloService helloService;
    
        /** * @description: 模拟调用 * @author cheng * @dateTime 2018/4/26 14:42 */
        @RequestMapping(value = "/hello")
        public String hello() {
            return helloService.showPort();
        }
    
    }

启动项目

*  Ahut-Eureka-Server（注册中心）
 *  Ahut-Eureka-Client-One（AHUT-EUREKA-CLIENT服务一）
 *  Ahut-Eureka-Client-Two（AHUT-EUREKA-CLIENT服务二）
 *  Ahut-Service-Feign（AHUT-SERVICE-FEIGN服务消费者）

访问eureka  
![这里写图片描述][70 3]

## 此时的项目架构 ##

![这里写图片描述][70 4]

[70]: /images/20220526/4dace33f904e427ba4a0857a36b8a357.png
[70 1]: /images/20220526/9fbd9b676aa84b73a2afc21b875cf65e.png
[70 2]: /images/20220526/50855adca06245f993cc09d3afdf141a.png
[70 3]: /images/20220526/bf1e44ba9ddd4c97b395da9b50f459b4.png
[70 4]: /images/20220526/291de1fb5ba1414487c18d45dd6b7f08.png