Feign是一個聲明式的僞Http客戶端,它使得寫Http客戶端變得更簡單。使用Feign,只須要建立一個接口並註解。它具備可插拔的註解特性,可以使用Feign 註解和JAX-RS註解。Feign支持可插拔的編碼器和解碼器。Feign默認集成了Ribbon,並和Eureka結合,默認實現了負載均衡的效果。java
簡而言之:web
繼續用上一節的工程, 啓動eureka-server,端口爲1111; 啓動service-hi 兩次,端口分別爲222二、3333.spring
新建一個spring-boot工程,取名爲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,代碼以下:apache
<?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.example.springcloud</groupId> <artifactId>feign</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>feign</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.4.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> <spring-cloud.version>Finchley.SR1</spring-cloud.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId> </dependency> <!-- feign相關依賴--> <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>${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.xml文件,指定程序名爲service-feign,端口號爲5555,服務註冊地址爲http://localhost:1111/eureka/ ,代碼以下:瀏覽器
server.port = 5555 spring.application.name = service-feign eureka.client.serviceUrl.defaultZone = http://localhost:1111/eureka/
定義一個feign接口,經過@ FeignClient(「服務名」),來指定調用哪一個服務。好比在代碼中調用了service-hi服務的「/hi」接口,代碼以下:app
package com.example.springcloud.feign.service;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(value = "service-hi")
public interface SchedualServiceHi {
@RequestMapping(value = "/hi",method = RequestMethod.GET)
String sayHiFromClientOne(@RequestParam(value = "name") String name);
}
在Web層的controller層,對外暴露一個」/hi」的API接口,經過上面定義的Feign客戶端SchedualServiceHi 來消費服務。代碼以下負載均衡
package com.example.springcloud.feign.web; import com.example.springcloud.feign.service.SchedualServiceHi; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; @RestController public class HiController { @Autowired SchedualServiceHi schedualServiceHi; @RequestMapping(value = "/hi",method = RequestMethod.GET) public String sayHi(@RequestParam String name){ return schedualServiceHi.sayHiFromClientOne(name); } }
在程序的啓動類ServiceFeignApplication ,加上@EnableFeignClients註解開啓Feign的功能:maven
package com.example.springcloud.feign; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.openfeign.EnableFeignClients; @EnableDiscoveryClient @EnableFeignClients @SpringBootApplication public class FeignApplication { public static void main(String[] args) { SpringApplication.run(FeignApplication.class, args); } }
啓動程序,屢次訪問http://localhost:5555/hi?name=forezp,瀏覽器交替顯示:spring-boot