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采用的是接口加注解
• feign 整合了ribbon

二、準備工作

繼續用上一節的工程： 啟動eureka-server，端口為8761; 啟動service-hi 兩次，端口分別為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"?> <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/> <!-- lookup parent from repository --></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>

向服務注冊中心注冊它自己，這時service-feign既是服務提供者，也是服務消費者,配置文件application.yml

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

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

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

定義一個feign接口類,通過@ FeignClient（“服務名”），來指定調用哪個服務：

/*** 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層的controllrt:

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

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) public interface StoreClient {//.. }

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

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

總結

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