史上最简单的SpringCloud教程 | 第三篇: 服务消费者（Feign）

不念不忘少年蓝@ 2022-06-09 05:13 170阅读 0赞

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springcloud（25） ![arrow_triangle_20_down.jpg][]

目录[(?)][Link 1][\[+\]][Link 1]

> 转载请标明出处：   
> [http://blog.csdn.net/forezp/article/details/69808079][http_blog.csdn.net_forezp_article_details_69808079]   
> 本文出自[方志朋的博客][Link 2]

上一篇文章，讲述了如何通过RestTemplate+Ribbon去消费服务，这篇文章主要讲述如何通过Feign去消费服务。

### 一、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。

简而言之：

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

### 二、准备工作 ###

继续用上一节的工程， 启动eureka-server，端口为8761; 启动service-hi 两次，端口分别为8762 、8773.

### 三、创建一个feign的服务 ###

新建一个[spring][]\-boot工程，取名为serice-feign，在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-eureka、Web的起步依赖spring-boot-starter-web，代码如下：

<?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.forezp</groupId>
        <artifactId>service-feign</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <name>service-feign</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.2.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>
        </properties>
    
        <dependencies>
            <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-web</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>Dalston.RC1</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>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>
    
    
    </project>
    
       
        
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在工程的配置文件application.yml文件，指定程序名为service-feign，端口号为8765，服务注册地址为[http://localhost:8761/eureka/][http_localhost_8761_eureka] ，代码如下：

eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:8761/eureka/
    server:
      port: 8765
    spring:
      application:
        name: service-feign
    
       
        
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在程序的启动类ServiceFeignApplication ，加上@EnableFeignClients注解开启Feign的功能：

@SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients
    public class ServiceFeignApplication { 
    
        public static void main(String[] args) {
            SpringApplication.run(ServiceFeignApplication.class, args);
        }
    }
    
    
       
        
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定义一个feign接口，通过@ FeignClient（“服务名”），来指定调用哪个服务。比如在代码中调用了service-hi服务的“/hi”接口，代码如下：

/** * Created by fangzhipeng on 2017/4/6. */
    @FeignClient(value = "service-hi")
    public interface SchedualServiceHi { 
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        String sayHiFromClientOne(@RequestParam(value = "name") String name);
    }
    
    
       
        
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在Web层的controller层，对外暴露一个”/hi”的API接口，通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下：

@RestController
    public class HiController { 
    
        @Autowired
        SchedualServiceHi schedualServiceHi;
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        public String sayHi(@RequestParam String name){
            return schedualServiceHi.sayHiFromClientOne(name);
        }
    }
    
    
       
        
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启动程序，多次访问[http://localhost:8765/hi?name=forezp][http_localhost_8765_hi_name_forezp],浏览器交替显示：

> hi forezp,i am from port:8762
> 
> hi forezp,i am from port:8763

Feign源码解析：[http://blog.csdn.net/forezp/article/details/73480304][http_blog.csdn.net_forezp_article_details_73480304]

本文源码下载：   
[https://github.com/forezp/SpringCloudLearning/tree/master/chapter3][https_github.com_forezp_SpringCloudLearning_tree_master_chapter3]

### 五、参考资料 ###

[spring-cloud-feign][]

[category_icon.jpg]: /images/20220609/249b5a1eddad4f048fa89a33441487e7.png
[arrow_triangle_20_down.jpg]: /images/20220609/1dd2ba7f1df147829d2e2e04e945e8df.png
[Link 1]: http://blog.csdn.net/forezp/article/details/69808079#
[http_blog.csdn.net_forezp_article_details_69808079]: http://blog.csdn.net/forezp/article/details/69808079
[Link 2]: http://blog.csdn.net/forezp
[spring]: http://lib.csdn.net/base/javaee
[http_localhost_8761_eureka]: http://localhost:8761/eureka/
[http_localhost_8765_hi_name_forezp]: http://localhost:8765/hi?name=forezp
[http_blog.csdn.net_forezp_article_details_73480304]: http://blog.csdn.net/forezp/article/details/73480304
[https_github.com_forezp_SpringCloudLearning_tree_master_chapter3]: https://github.com/forezp/SpringCloudLearning/tree/master/chapter3
[spring-cloud-feign]: http://projects.spring.io/spring-cloud/spring-cloud.html#spring-cloud-feign