一、Feign简介
- Feign是一个声明式的伪Http客户端
- 使用Feign，只需要创建一个接口并注解
- 有可插拔的注解特性，使用Feign 注解和JAX-RS注解
- Feign支持可插拔的编码器和解码器
- Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果
- 整合了Hystrix，具有熔断的能力
二、准备工作
启动eureka-server，端口为8761; 启动service-hi 两次，端口分别为8762 、8773.
新建一个父工程与第一节相同建一个spring-boot工程，取名为serice-feign，在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-netflix-eureka-client、Web的起步依赖spring-boot-starter-web，代码如下：
<?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 https://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> <name>service-feign</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.3.RELEASE</version> </parent> <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> <exclusions> <exclusion> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId> </exclusion> </exclusions> </dependency> </dependencies> </project>
在工程的配置文件application.yml文件，指定程序名为service-feign，端口号为8765，服务注册地址为http://localhost:8761/eureka/ ，代码如下：
server:
port: 8765
spring:
application:
name: service-feign
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
在程序的启动类ServiceFeignApplication ，加上@EnableFeignClients注解开启Feign的功能：
package com.forezp.servicefeign; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; import org.springframework.cloud.openfeign.EnableFeignClients; @SpringBootApplication @EnableEurekaClient @EnableDiscoveryClient @EnableFeignClients public class ServiceFeignApplication { public static void main(String[] args) { SpringApplication.run(ServiceFeignApplication.class, args); } }
定义一个feign接口，通过@ FeignClient（“服务名”），来指定调用哪个服务。比如在代码中调用了service-hi服务的“/hi”接口，代码如下：
package com.forezp.servicefeign.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; /** * @Auther: chengmr * @Date: 2020/6/23 14:41 * @Description: */ @FeignClient(value = "service-hi") public interface SchedualServiceHi { @RequestMapping(value = "/hi",method = RequestMethod.GET) String sayHiFromClientOne(@RequestParam(value = "name") String name); }
在Web层的controller层，对外暴露一个”/hello”的API接口，通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下：
package com.forezp.servicefeign.controller; import com.forezp.servicefeign.service.SchedualServiceHi; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; /** * @Auther: chengmr * @Date: 2020/6/23 14:43 * @Description: */ @RestController public class HiController { //编译器报错，无视。 因为这个Bean是在程序启动的时候注入的，编译器感知不到，所以报错。 @Autowired SchedualServiceHi schedualServiceHi; @RequestMapping("/hello") public String sayHi(@RequestParam String name){ return schedualServiceHi.sayHiFromClientOne(name); } }
启动程序，多次访问http://localhost:8765/hello?name=forezp,浏览器交替显示：
源码下载：IT虾米网
