概述
Feign 是一个声明式的伪 Http 客户端，它使得写 Http 客户端变得更简单。使用 Feign，只需要创建一个接口并注解。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
- Feign 采用的是基于接口的注解
- Feign 整合了 ribbon
创建服务消费者
创建一个工程名为 hello-spring-cloud-web-admin-feign 的服务消费者项目，pom.xml 配置如下：
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>com.ycq</groupId> <artifactId>hello-spring-cloud-dependencies</artifactId> <version>1.0.0-SNAPSHOT</version> <relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath> </parent> <artifactId>hello-spring-cloud-web-admin-feign</artifactId> <packaging>jar</packaging> <name>hello-spring-cloud-web-admin-feign</name> <dependencies> <!-- Spring Boot Begin --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!-- Spring Boot End --> <!-- Spring Cloud Begin --> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> </dependency> <!-- Spring Cloud End --> <!-- 解决 thymeleaf 模板引擎一定要执行严格的 html5 格式校验问题 --> <dependency> <groupId>net.sourceforge.nekohtml</groupId> <artifactId>nekohtml</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <mainClass>com.ycq.hello.spring.cloud.web.admin.feign.WebAdminFeignApplication</mainClass> </configuration> </plugin> </plugins> </build> </project>
主要是增加了 Feign 的依赖
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> </dependency>
Application
通过 @EnableFeignClients 注解开启 feign 功能
package com.ycq.hello.spring.cloud.web.admin.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; @SpringBootApplication @EnableDiscoveryClient @EnableFeignClients public class WebAdminFeignApplication { public static void main(String[] args) { SpringApplication.run(WebAdminFeignApplication.class, args); } }
application.yml
设置程序端口号为：8765
spring: application: name: hello-spring-cloud-web-admin-feign thymeleaf: cache: false mode: LEGACYHTML5 encoding: UTF-8 servlet: content-type: text/html server: port: 8765 eureka: client: serviceUrl: defaultZone: http://localhost:8761/eureka/
创建 Feign 接口
通过 @FeignClient("服务名") 注解来指定调用哪个服务。代码如下：
package com.ycq.hello.spring.cloud.web.admin.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 = "hello-spring-cloud-service-admin") public interface AdminService { @RequestMapping(value = "hi", method = RequestMethod.GET) public String sayHi(@RequestParam(value = "message") String message); }
创建测试用的 Controller
package com.ycq.hello.spring.cloud.web.admin.feign.controller; import com.ycq.hello.spring.cloud.web.admin.feign.service.AdminService; 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 AdminController { @Autowired private AdminService adminService; @RequestMapping(value = "hi", method = RequestMethod.GET) public String sayHi(@RequestParam String message) { return adminService.sayHi(message); } }
测试访问
在浏览器上多次访问 http://localhost:8765/hi?message=HelloFeign
浏览器交替显示：
You message is HelloFeign，You port is 8762 You message is HelloFeign，You port is 8763
请求成功则表示我们已经成功实现了 Feign 功能来访问不同端口的实例
