【SpringCloud教程】2.SpringCloud 负载均衡Loadbalancer和OpenFeign
简介
在SpringCloud第一代中是通过Ribbon负载均衡，第二代是在Ribbon基础上封装了LoadBalancer。本文采用的注册中心是SpringCloud Alibaba Nacos，如果采用SpringCloud Eureka可直接改依赖。LoadBalancer和OpenFeign都属于SpringCloud第二代的产品。
在SpringBoot中可以通过一下方式达到项目通讯：
- RestTemplate结合@LoadBalanced（负载均衡）
- LoadBalancerClient自定义负载均衡策略
- Feign（负载均衡）
- OkHttp
- HttpClient
代码结构如下图：
服务提供者实例
代码一模一样只是端口不同，代码如下：
user-api-9001
@RestController
public class UserService {
@GetMapping("getUser")
public String getUser(){
return "terry-9001";
}
}
user-api-9002
@RestController
public class UserService {
@GetMapping("getUser")
public String getUser(){
return "terry-9002";
}
}
pom.xml依赖
<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>4.0.0modelVersion>
<artifactId>user-consumerartifactId>
<properties>
<maven.compiler.source>8maven.compiler.source>
<maven.compiler.target>8maven.compiler.target>
properties>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.3.2.RELEASEversion>
parent>
<dependencies>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>com.alibaba.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
<version>2.2.6.RELEASEversion>
dependency>
dependencies>
project>
服务消费
服务消费者依赖：
<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>4.0.0modelVersion>
<artifactId>user-consumerartifactId>
<properties>
<maven.compiler.source>8maven.compiler.source>
<maven.compiler.target>8maven.compiler.target>
properties>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.3.2.RELEASEversion>
parent>
<dependencies>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>com.alibaba.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
<version>2.2.6.RELEASEversion>
dependency>
dependencies>
project>
RestTemplate结合@LoadBalanced实现负载均衡
起一个配置类，配置RestTemplate和@LoadBanlanced
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 RestTemplateConfig {
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
Controller配置
@RestController
public class UserService {
@Autowired
private RestTemplate restTemplate;
@GetMapping("/restTemplateGetUser")
public String restTemplateGetUser(){
return restTemplate.getForObject("http://user-api/getUser", String.class);
}
}
打开浏览器输入地址：http://localhost:8080/restTemplateGetUser
多次刷新可以看到是交替运行的。
使用LoadBalancerClient实现负载均衡
@RestController
public class UserService {
@Autowired
private RestTemplate restTemplate;
@Autowired
private LoadBalancerClient loadBalancerClient;
/**
* 使用 LoadBalancerClient实现负载均衡
* @return
*/
@GetMapping("/loadBalancerClientGetUser")
public String loadBalancerClientGetUser(){
ServiceInstance choose = loadBalancerClient.choose("user-api");
System.out.println(choose.getUri().toString());
return restTemplate.getForObject(choose.getUri().toString() + "/getUser", String.class);
}
}
使用OpenFeign实现负载均衡
消费者pom.xml
<?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>
<artifactId>user-consumer</artifactId>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.3.2.RELEASE</version>
</parent>
<dependencies>
<!-- SpringBoot web组件 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- nacos 注册中心 -->
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
<version>2.2.6.RELEASE</version>
</dependency>
<!-- openfeign 客户端 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
<version>2.2.6.RELEASE</version>
</dependency>
</dependencies>
</project>
启动类配置
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@EnableFeignClients
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
openFeign配置类
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
@Component
// 指定服务名称
@FeignClient("user-api")
public interface UserFeign {
/**
* 对应 user-api 的getUser
* @return
*/
@GetMapping("getUser")
public String getUser();
}
Controller
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserService {
@Autowired
private UserFeign userFeign;
/**
* 使用 openFeign实现负载均衡
* @return
*/
@GetMapping("/openFeignGetUser")
public String openFeignGetUser(){
return userFeign.getUser();
}
}
打开浏览器输入地址：http://localhost:8080/restTemplateGetUser
多次刷新可以看到是交替运行的。
