简介
RestTemplate
Spring用于同步client端的核心类,简化了与http服务的通信,并满足RESTful原则,程序代码可以给它提供URL,并提取结果。默认情况下,RestTemplate默认依赖jdk的HTTP连接工具。
Ribbon
Spring Cloud Ribbon是一个基于HTTP和TCP的客户端负载均衡工具,它基于Netflix Ribbon实现。通过Spring Cloud的封装,可以让我们轻松地将面向服务的REST模版请求自动转换成客户端负载均衡的服务调用。Spring Cloud Ribbon几乎存在于每一个Spring Cloud构建的微服务和基础设施中。因为微服务间的调用,API网关的请求转发等内容,实际上都是通过Ribbon来实现的,包括Feign,它也是基于Ribbon实现的工具。
在Spring Cloud中,当Ribbon与Eureka配合使用时,Ribbon可自动从Eureka Server获取服务提供者地址列表,并基于负载均衡算法,选择其中一个服务提供者实例。
启动注册中心和服务提供者
https://blog.csdn.net/miaodichiyou/article/details/104160284
1、启动SpringCloud高可用服务注册中心(Eureka)搭建的注册中心
2、在springcloud-eureka-provider项目Hi_provider.java文件中添加一个controller,对外提供服务 "/hi"
package org.springcloud.eureka.provider;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@SpringBootApplication
@EnableEurekaClient
public class Hi_provider
{
public static void main( String[] args )
{
SpringApplication.run(Hi_provider.class, args);
}
@RestController
public class HiController {
@Value("${server.port}")
String port;
@GetMapping("/hi")
public String Home(@RequestParam String name){
return "hi "+name+",This is from serverport:"+port;
}
}
}
启动三个springcloud-eureka-provider实例,端口分别为8001,8002和8003
创建服务消费者
添加依赖包文件POM.xml
<?xml version="1.0"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.springcloud</groupId>
<artifactId>springcloud-root</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>springcloud-ribbon</artifactId>
<name>springcloud-ribbon</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<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-netflix-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</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>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
配置application.yml文件
spring:
application:
name: springcloud-ribbon
freemarker:
prefer-file-system-access: false
security:
user:
name: admin
password: 123456
server:
port: 8100
eureka:
instance:
hostname: eureka-ribbon.com
instance-id: eureka-ribbon
client:
service-url:
defaultZone: http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer1.com:8897/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer2.com:8898/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer3.com:8899/eureka/
修改C:\Windows\System32\drivers\etc\hosts
127.0.0.1 eureka-ribbon.com
添加服务消费者启动类
- RibbonApplication.java
package org.springcloud.ribbon;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class RibbonApplication {
public static void main(String[] args) {
SpringApplication.run(RibbonApplication.class, args);
}
}
添加RESTful API接口
调用springcloud-eureka-provider实例的API接口"/hi",即消费服务。由于springcloud-eureka-provider为三个实例(端口8001、8002、8003),在调用时希望做到轮流访问这三个实例,这时需要将RestTemplate和Ribbon结合进行负载均衡。只需要在程序的IOC容器中注入一个restTemplate的Bean,并加上@LoadBalanced注解,此时RestTemplate就结合了Ribbon开启了负载均衡功能。
- RestTemplateConfig.java
package org.springcloud.ribbon;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;
@Configuration
public class RestTemplateConfig {
@Bean
@LoadBalanced
public RestTemplate restTemplate(){
HttpComponentsClientHttpRequestFactory httpRequestFactory = new HttpComponentsClientHttpRequestFactory();
httpRequestFactory.setConnectionRequestTimeout(30000);
httpRequestFactory.setConnectTimeout(30000);
httpRequestFactory.setReadTimeout(30000);
return new RestTemplate(httpRequestFactory);
}
}
添加service消费服务提供者实例提供的服务
编写一个RibbonService类,在该类的hi()方法用restTemplate调用springcloud-eureka-provider的API接口,uri上不需要使用硬编码(如IP地址),只需写服务名springcloud-eureka-provider即可。
- RibbonService.java
package org.springcloud.ribbon;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class RibbonService {
@Autowired
RestTemplate restTemplate;
public String hi(String name){
return restTemplate.getForObject("http://springcloud-eureka-provider/hi?name="+name,String.class);
}
}
注:getForObject中的url springcloud-eureka-provider为springcloud-eureka-provider项目(服务提供者)的应用名称,也就是在创建springcloud-eureka-provider项目时在配置文件中配置的spring.application.name=springcloud-eureka-provider。hi为springcloud-eureka-provider项目中接口的地址(controller), name是请求参数。
创建controller,调用service中的方法
编写一个RibbonController类
package org.springcloud.ribbon;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class RibbonController {
@Autowired
private RibbonService ribbonService;
@GetMapping("/hi")
public String hi(@RequestParam(required = false,defaultValue = "zhaojq") String name){
return ribbonService.hi(name);
}
}
启动springcloud-ribbon工程
查看Eureka注册中心
运行启动类,访问http://eureka-peer1.com:8897/
http://eureka-peer2.com:8898/,http://eureka-peer3.com:8899/ 结果同上。
服务消费者实例已成功注册。
在浏览器地址栏访问ribbon项目中的controller
在浏览器多次访问http://localhost:8100/hi?name=zhaojq,浏览器会轮流显示如下
当一直刷新http://localhost:8100/hi?name=zhaojq时可以发现浏览器交替显示端口8001,8002和8003,说明已经实现客户端的负载均衡,并且Ribbon默认采用轮询的负载均衡算法。
Ribbon负载均衡策略
自定义负载均衡策略(随机策略)
修改springcloud-ribbon工程的application.yml配置文件添加如下配置:
# 自定义配置负载均衡策略
Load_Balance:
ribbon:
NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule
Load_Balance为需要负载的服务地址,com.netflix.loadbalancer.RandomRule为服务策略。此处我们配置为随机策略
修改RestTemplateConfig配置类:
@Bean
public IRule ribbonRule() {
return new RandomRule();//实例化与配置文件对应的策略类
}
修改RibbonController
package org.springcloud.ribbon;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class RibbonController {
@Autowired
private RibbonService ribbonService;
@Autowired
private LoadBalancerClient loadBalancerClient;
@GetMapping("/hi")
public String hi(@RequestParam(required = false,defaultValue = "zhaojq")String name){
this.loadBalancerClient.choose("Load_Balance");
return ribbonService.hi(name);
}
}
LoadBalancerClient(RibbonLoadBalancerClient是实现类)在初始化的时候(execute方法),会通过ILoadBalance(BaseLoadBalancer是实现类)向Eureka注册中心获取服务注册列表,并且每10s一次向EurekaClient发送“ping”,来判断服务的可用性,如果服务的可用性发生了改变或者服务数量和之前的不一致,则从注册中心更新或者重新拉取。LoadBalancerClient有了这些服务注册列表,就可以根据具体的IRule来进行负载均衡。
重新启动springcloud-ribbon项目,访问http://eureka-ribbon.com:8100/hi?name=zhaojq
在命令窗口curl http://eureka-ribbon.com:8100/hi,发现Ribbon已经实现随机负载均衡策略