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

Love The Way You Lie 2024-04-19 09:22 63阅读 0赞

## 服务间的相互调用之feign ##

上一篇文章，讲述了通过restTemplate+ribbon去消费服务，这篇文章主要讲述通过feign去消费服务。

### 一、Feign简介 ###

Feign是一个声明式的web服务客户端，它使得写web服务变得更简单。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，包括Feign 注解和JAX-RS注解。Feign同时支持可插拔的编码器和解码器。Spring cloud对Spring mvc添加了支持，同时在spring web中次用相同的HttpMessageConverter。当我们使用feign的时候，spring cloud 整和了Ribbon和eureka去提供负载均衡。

简而言之：

*  feign采用的是接口加注解
 *  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 ###

创建一个spring-boot工程，取名为：serice-feign,它的pom文件为：

<?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>

向服务注册中心注册它自己，这时service-ribbon既是服务提供者，也是服务消费者,配置文件application.yml

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

在程序的入口类，需要通过注解@EnableFeignClients来开启feign:

@SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients
    public class ServiceFeignApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(ServiceFeignApplication.class, args);
        }
    }

定义一个feign接口类,通过@ FeignClient（“服务名”），来指定调用哪个服务：

/**
     * 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);
    }

在web层的controllrt:

@RestController
    public class HiController {
    
        @Autowired
        SchedualServiceHi schedualServiceHi;
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        public String sayHi(@RequestParam String name){
            return schedualServiceHi.sayHiFromClientOne(name);
        }
    }

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

#### 四、更改feign的配置 ####

在声明feignclient的时候，不仅要指定服务名，同时需要制定服务配置类：

@FeignClient(name = "stores", configuration = FooConfiguration.class)
    public interface StoreClient {
        //..
    }

重写配置，需要加@Configuration注解，并重写下面的两个bean,栗子：

@Configuration
    public class FooConfiguration {
        @Bean
        public Contract feignContractg() {
            return new feign.Contract.Default();
        }
    
        @Bean
        public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
            return new BasicAuthRequestInterceptor("user", "password");
        }
    }

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][]

转载于:https://my.oschina.net/abcijkxyz/blog/3057102

[http_localhost_8765_hi_name_forezp]: https://link.jianshu.com?t=http://localhost:8765/hi?name=forezp
[https_github.com_forezp_SpringCloudLearning_tree_master_chapter3]: https://link.jianshu.com?t=https://github.com/forezp/SpringCloudLearning/tree/master/chapter3
[spring-cloud-feign]: https://link.jianshu.com?t=http://projects.spring.io/spring-cloud/spring-cloud.html#spring-cloud-feign