【微服务架构 - 08 - Spring Cloud】05 创建服务消费者（Feign)

约定不等于承诺〃 2022-03-22 18:18 141阅读 0赞

## 概述 ##

--------------------

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，它使用 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效果

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

## 创建服务消费者 ##

--------------------

创建一个工程名为 `hello-spring-cloud-web-admin-feign` 的服务消费者项目，  
`pom.xml` 配置如下：

<?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>
    
        <parent>
            <groupId>com.yuu</groupId>
            <artifactId>hello-spring-cloud-dependencies</artifactId>
            <version>1.0.0-SNAPSHOT</version>
            <relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath>
        </parent>
    
        <artifactId>hello-spring-cloud-web-admin-feign</artifactId>
        <packaging>jar</packaging>
    
        <name>hello-spring-cloud-web-admin-feign</name>
        <inceptionYear>2019-Now</inceptionYear>
    
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-tomcat</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-thymeleaf</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-actuator</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
            
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
            
    
            
            <dependency>
                <groupId>net.sourceforge.nekohtml</groupId>
                <artifactId>nekohtml</artifactId>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                    <configuration>
                        <mainClass>com.funtl.hello.spring.cloud.web.admin.feign.WebAdminFeignApplication</mainClass>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    </project>

主要是增加了 Feign 的依赖

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

## Application ##

--------------------

package com.yuu.hello.spring.cloud.service.admin;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    
    /**
     * @Classname ServiceAdminApplication
     * @Date 2019/1/28 22:50
     * @Created by Yuu
     */
    @SpringBootApplication
    @EnableEurekaClient
    public class ServiceAdminApplication {
        public static void main(String[] args) {
            SpringApplication.run(ServiceAdminApplication.class, args);
        }
    }

## application.yml ##

--------------------

设置程序端口号为：`8765`

spring:
      application:
        name: hello-spring-cloud-web-admin-fegin
      thymeleaf:
        cache: false
        mode: HTML
        encoding: UTF-8
        servlet:
          content-type: text/html
    server:
      port: 8765
    
    eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:8761/eureka/

## 创建 Feign 接口 ##

--------------------

通过 `@FeignClient("服务名")` 注解来指定调用那个服务。代码如下：

package com.yuu.hello.spring.cloud.web.admin.feign.service;
    
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    
    /**
     * @Classname AdminService
     * @Date 2019/1/29 13:09
     * @Created by Yuu
     */
    @FeignClient(value = "hello-spring-cloud-service-admin")
    public interface AdminService {
    
        @RequestMapping(value = "hi", method = RequestMethod.GET)
        public String sayHi(@RequestParam(value = "message") String message);
    }

## 创建测试用的 Controller ##

--------------------

package com.yuu.hello.spring.cloud.web.admin.feign.controller;
    
    import com.yuu.hello.spring.cloud.web.admin.feign.service.AdminService;
    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;
    
    /**
     * @Classname AdminController
     * @Date 2019/1/29 13:11
     * @Created by Yuu
     */
    @RestController
    public class AdminController {
    
        @Autowired
        private AdminService adminService;
    
        @RequestMapping(value = "hi", method = RequestMethod.GET)
        public String sayHi(String message) {
            return adminService.sayHi(message);
        }
    }

## 测试访问 ##

--------------------

在浏览器上多次访问 [http://localhost:8765/hi?message=HelloFeign][http_localhost_8765_hi_message_HelloFeign]

浏览器交替显示：

![在这里插入图片描述][20190129133504287.png]

![在这里插入图片描述][20190129133525793.png]

[http_localhost_8765_hi_message_HelloFeign]: http://localhost:8765/hi?message=HelloFeign
[20190129133504287.png]: /images/20220322/0f12ca8ac1094bd4a419c04547c4fb04.png
[20190129133525793.png]: /images/20220322/ad4c293c44314e39958fcfda3d4319a2.png