feign(什么是feign)

一、Feign簡介

Feign是一個聲明式的偽Http客戶端,它使得寫Http客戶端變得更簡單。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,可使用Feign 注解和JAX-RS注解。Feign支持可插拔的編碼器和解碼器。Feign默認集成了Ribbon,并和Eureka結合,默認實現了負載均衡的效果。

簡而言之:

• Feign 采用的是基于接口的注解

• 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

新建一個spring-boot工程,取名為serice-feign,在它的pom文件引入Feign的起步依賴spring-cloud-starter-feign、Eureka的起步依賴spring-cloud-starter-eureka、Web的起步依賴spring-boot-starter-web,代碼如下:

<?xmlversion="1.0"encoding="UTF-8"?><projectxmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.8.RELEASE</version><relativePath/><!--lookupparentfromrepository--></parent><groupId>com.free</groupId><artifactId>serice-feign</artifactId><version>0.0.1-SNAPSHOT</version><name>serice-feign</name><description>DemoprojectforSpringBoot</description><properties><java.version>1.8</java.version><spring-cloud.version>Greenwich.SR3</spring-cloud.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</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>${spring-cloud.version}</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></project>

在工程的配置文件application.yml文件,指定程序名為service-feign,端口號為8765,服務注冊地址為http://localhost:8761/eureka/ ,代碼如下:

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

在程序的啟動類ServiceFeignApplication ,加上@EnableFeignClients注解開啟Feign的功能:

importorg.springframework.boot.SpringApplication;importorg.springframework.boot.autoconfigure.SpringBootApplication;importorg.springframework.cloud.client.discovery.EnableDiscoveryClient;importorg.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication@EnableDiscoveryClient@EnableFeignClientspublicclassSericeFeignApplication{publicstaticvoidmain(String[]args){SpringApplication.run(SericeFeignApplication.class,args);}}

定義一個feign接口,通過@ FeignClient(“服務名”),來指定調用哪個服務。比如在代碼中調用了service-hi服務的“/hi”接口,代碼如下:

@Service@FeignClient(value="service-hi")publicinterfaceSchedualServiceHi{@RequestMapping(value="/hi",method=RequestMethod.GET)StringsayHiFromClientOne(@RequestParam(value="name")Stringname);}

在Web層的controller層,對外暴露一個”/hi”的API接口,通過上面定義的Feign客戶端SchedualServiceHi 來消費服務。代碼如下:

@RestControllerpublicclassHiController{@AutowiredSchedualServiceHischedualServiceHi;@RequestMapping(value="/hi",method=RequestMethod.GET)publicStringsayHi(@RequestParamStringname){returnschedualServiceHi.sayHiFromClientOne(name);}}

啟動程序,多次訪問http://localhost:8765/hi?name=zz,瀏覽器交替顯示:

hi zz,i am from port:8762

hi zz,i am from port:8763

Feign源碼解析:http://blog.csdn.net/forezp/article/details/73480304

本文源碼下載:https://gitee.com/freesystem/SpringCloudDemo/tree/master/serice-feign

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