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，它使用 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.yuu</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><inceptionYear>2019-Now</inceptionYear><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.funtl.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
package com.yuu.hello.spring.cloud.service.admin;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;/*** @Classname ServiceAdminApplication* @Date 2019/1/28 22:50* @Created by Yuu*/
@SpringBootApplication
@EnableEurekaClient
public class ServiceAdminApplication {public static void main(String[] args) {SpringApplication.run(ServiceAdminApplication.class, args);}
}application.yml
设置程序端口号为：8765
spring:application:name: hello-spring-cloud-web-admin-feginthymeleaf:cache: falsemode: HTMLencoding: UTF-8servlet:content-type: text/html
server:port: 8765eureka:client:serviceUrl:defaultZone: http://localhost:8761/eureka/创建 Feign 接口
通过 @FeignClient("服务名") 注解来指定调用那个服务。代码如下：
package com.yuu.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;/*** @Classname AdminService* @Date 2019/1/29 13:09* @Created by Yuu*/
@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.yuu.hello.spring.cloud.web.admin.feign.controller;import com.yuu.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.RestController;/*** @Classname AdminController* @Date 2019/1/29 13:11* @Created by Yuu*/
@RestController
public class AdminController {@Autowiredprivate AdminService adminService;@RequestMapping(value = "hi", method = RequestMethod.GET)public String sayHi(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：
