史上最簡單的SpringCloud教程 | 第三篇: 服務消費者（Feign）

上一篇文章，講述了通過restTemplate+ribbon去消費服務，這篇文章主要講述通過feign去消費服務。

一、Feign簡介

Feign是一個聲明式的web服務客戶端，它使得寫web服務變得更簡單。使用Feign,只需要創建一個介面並註解。它具有可插拔的註解特性，包括Feign 註解和JAX-RS註解。Feign同時支持可插拔的編碼器和解碼器。spring cloud對Spring mvc添加了支持，同時在spring web中次用相同的HttpMessageConverter。當我們使用feign的時候，spring cloud 整和了Ribbon和eureka去提供負載均衡。

簡而言之：

• feign採用的是介面加註解
• feign 整合了ribbon

二、準備工作

繼續用上一節的工程： 啟動eureka-server，埠為8761; 啟動service-hi 兩次，埠分別為8762 、8773.

三、創建一個feign的服務

創建一個spring-boot工程，取名為：serice-feign,它的pom文件為：

<?xml version="1.0" encoding="UTF-8"?>n<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"n xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">n <modelVersion>4.0.0</modelVersion>nn <groupId>com.forezp</groupId>n <artifactId>service-feign</artifactId>n <version>0.0.1-SNAPSHOT</version>n <packaging>jar</packaging>nn <name>service-feign</name>n <description>Demo project for Spring Boot</description>nn <parent>n <groupId>org.springframework.boot</groupId>n <artifactId>spring-boot-starter-parent</artifactId>n <version>1.5.2.RELEASE</version>n <relativePath/> <!-- lookup parent from repository -->n </parent>nn <properties>n <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>n <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>n <java.version>1.8</java.version>n </properties>nn <dependencies>n <dependency>n <groupId>org.springframework.cloud</groupId>n <artifactId>spring-cloud-starter-eureka</artifactId>n </dependency>n <dependency>n <groupId>org.springframework.cloud</groupId>n <artifactId>spring-cloud-starter-feign</artifactId>n </dependency>n <dependency>n <groupId>org.springframework.boot</groupId>n <artifactId>spring-boot-starter-web</artifactId>n </dependency>nn <dependency>n <groupId>org.springframework.boot</groupId>n <artifactId>spring-boot-starter-test</artifactId>n <scope>test</scope>n </dependency>n </dependencies>nn <dependencyManagement>n <dependencies>n <dependency>n <groupId>org.springframework.cloud</groupId>n <artifactId>spring-cloud-dependencies</artifactId>n <version>Dalston.RC1</version>n <type>pom</type>n <scope>import</scope>n </dependency>n </dependencies>n </dependencyManagement>nn <build>n <plugins>n <plugin>n <groupId>org.springframework.boot</groupId>n <artifactId>spring-boot-maven-plugin</artifactId>n </plugin>n </plugins>n </build>nn <repositories>n <repository>n <id>spring-milestones</id>n <name>Spring Milestones</name>n <url>https://repo.spring.io/milestone</url>n <snapshots>n <enabled>false</enabled>n </snapshots>n </repository>n </repositories>n</project>n

向服務註冊中心註冊它自己，這時service-ribbon既是服務提供者，也是服務消費者,配置文件application.yml

eureka:n client:n serviceUrl:n defaultZone: http://localhost:8761/eureka/nserver:n port: 8765nspring:n application:n name: service-feignn

在程序的入口類，需要通過註解@EnableFeignClients來開啟feign:

@SpringBootApplicationn@EnableDiscoveryClientn@EnableFeignClientsnpublic class ServiceFeignApplication {nn public static void main(String[] args) {n SpringApplication.run(ServiceFeignApplication.class, args);n }n}n

定義一個feign介面類,通過@ FeignClient（「服務名」），來指定調用哪個服務：

/**n * Created by fangzhipeng on 2017/4/6.n */n@FeignClient(value = "service-hi")npublic interface SchedualServiceHi {n @RequestMapping(value = "/hi",method = RequestMethod.GET)n String sayHiFromClientOne(@RequestParam(value = "name") String name);n}n

在web層的controllrt:

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

訪問 http://localhost:8765/hi?name=forezp, 瀏覽器交替顯示：

hi forezp,i am from port:8762

hi forezp,i am from port:8763

四、更改feign的配置

在聲明feignclient的時候，不僅要指定服務名，同時需要制定服務配置類：

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

重寫配置，需要加@Configuration註解，並重寫下面的兩個bean,栗子：

@Configurationnpublic class FooConfiguration {n @Beann public Contract feignContractg() {n return new feign.Contract.Default();n }nn @Beann public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {n return new BasicAuthRequestInterceptor("user", "password");n }n}n

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五、參考資料

spring-cloud-feign