概述
在微服架构中，业务都会被拆分成一个独立的服务，服务与服务的通讯是基于 http restful 的。Springg cloud 有两种服务调用方式，一种是 ribbon + restTemplate，另一种是 feign。在这一篇文章首先讲解下基于 ribbon + rest。
Ribbon 简介
Ribbon 是一个负载均衡客户端，可以很好的控制 http 和 tcp 的一些行为。
准备工作
- 启动服务提供者（案例工程为：
hello-spring-cloud-server-admin） 端口号为：8762 - 修改配置文件的端口号为：
8763，启动后在 Eureka 中会注册两个实例，这相当于一个小集群
创建服务消费者
创建一个工程名为 hello-spring-cloud-web-admin-ribbon 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-ribbon</artifactId> <packaging>jar</packaging> <name>hello-spring-cloud-web-admin-ribbon</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-netflix-ribbon</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.ribbon.WebAdminRibbonApplication</mainClass> </configuration> </plugin> </plugins> </build> </project>
主要是增加了 Ribbon 的依赖
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-ribbon</artifactId> </dependency>
Application
通过 @EnableDiscoveryClient 注解注册到服务中心
package com.ycq.hello.spring.cloud.web.admin.ribbon; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; @SpringBootApplication @EnableDiscoveryClient public class WebAdminRibbonApplication { public static void main(String[] args) { SpringApplication.run(WebAdminRibbonApplication.class, args); } }
application.yml
设置程序端口号为：8764
spring: application: name: hello-spring-cloud-web-admin-ribbon thymeleaf: cache: false mode: LEGACYHTML5 encoding: UTF-8 servlet: content-type: text/html server: port: 8764 eureka: client: serviceUrl: defaultZone: http://localhost:8761/eureka/
Configuration
配置注入 RestTemplate 的 Bean，并通过 @LoadBalanced 注解表明开启负载均衡功能
package com.ycq.hello.spring.cloud.web.admin.ribbon.config; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.client.RestTemplate; @Configuration public class RestTemplateConfiguration { @Bean @LoadBalanced public RestTemplate restTemplate(){ return new RestTemplate(); } }
创建测试用的 Service
在这里我们直接用的程序名替代了具体的 URL 地址，在 Ribbon 中它会根据服务名来选择具体的服务实例，根据服务实例在请求的时候会用具体的 URL 替换掉服务名，代码如下：
package com.ycq.hello.spring.cloud.web.admin.ribbon.service; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import org.springframework.web.client.RestTemplate; @Service public class AdminService { @Autowired private RestTemplate restTemplate; public String sayHi(String message){ return restTemplate.getForObject("http://hello-spring-cloud-service-admin/hi?message=" + message, String.class); } }
创建测试用的 Controller
package com.ycq.hello.spring.cloud.web.admin.ribbon.controller; import com.ycq.hello.spring.cloud.web.admin.ribbon.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:8764/hi?message=HelloRibbon
浏览器交替显示：
You message is HelloRibbon，You port is 8762 You message is HelloRibbon，You port is 8763
