springcloud学习第三篇

一、客户端负载均衡组件Ribbon

1.添加依赖

<!-- 添加ribbon 依赖 -->
<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>

2.添加配置类

@Configuration
public class MyConfig {@Bean@LoadBalancedpublic RestTemplate restTemplate() {return new RestTemplate();}
}

3.使用

@RestController
public class Controller {@Autowiredprivate RestTemplate restTemplate;public string function() {ResponseEntity responseEntity = restTemplate.getForEntity("http://service-name/other/interface");}
}

4.常见负载均衡策略

默认轮询

4.1.随机

@Configuration
public class MyConfig {@Bean@LoadBalancedpublic RestTemplate restTemplate() {return new RestTemplate();}/*** 随机算法的负载均衡* @return 结果*/@Beanpublic IRule MyRule(){return new RandomRule();}
}

4.2.自定义

import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.Server;
import java.util.List;
import java.util.Random;public class CustomRule extends AbstractLoadBalancerRule {@Overridepublic Server choose(Object key) {// 获取所有可达的服务实例List<Server> reachableServers = getLoadBalancer().getReachableServers();if (reachableServers.isEmpty()) {return null;}// 示例：自定义过滤逻辑 - 只选择端口为 8081 的实例List<Server> filteredServers = reachableServers.stream().filter(server -> server.getPort() == 8081).collect(Collectors.toList());if (filteredServers.isEmpty()) {// 回退到随机选择return new Random().nextInt(reachableServers.size());}// 从过滤后的列表中选择return filteredServers.get(new Random().nextInt(filteredServers.size()));}
}

5.缺点

参数需要拼接到url上面

二、客户端负载均衡组件Feign

1.添加依赖

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

2.开启openFeign

@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients(basePackages = "com.jhk")
public class AppUserApplication {public static void main(String[] args) {SpringApplication.run(AppUserApplication.class, args);}
}

3.使用

// 调用其他服务
@FeignClient(name="service-name")
public interface serviceApi{@RequestMapping("/getData")String getData();
}

三、Feign源码

EnableFeignClients
org.springframework.cloud.openfeign.EnableFeignClients>org.springframework.cloud.openfeign.FeignClientsRegistrar # @Import({FeignClientsRegistrar.class}) 通过import注解方式加载FeignClientsRegistrar到容器>org.springframework.cloud.openfeign.FeignClientsRegistrar#registerBeanDefinitions # 将Bean 注册到 FeignClientsRegistrar>org.springframework.cloud.openfeign.FeignClientsRegistrar#registerFeignClients>org.springframework.cloud.openfeign.FeignClientsRegistrar#registerClientConfiguration # 扫描EnableFeignClients标签中的配置信息并注册>org.springframework.cloud.openfeign.FeignClientsRegistrar#registerFeignClient # 扫描所有@FeignClient注解的类注入spring容器>org.springframework.cloud.openfeign.FeignClientFactoryBean # 接口的代理Bean>org.springframework.cloud.openfeign.FeignClientFactoryBean#getObject>org.springframework.cloud.openfeign.FeignClientFactoryBean#getTarget>org.springframework.cloud.openfeign.FeignClientFactoryBean#loadBalance # 如果feignClient中没有url属性，会调用loadBalance完成自动负载调用>org.springframework.beans.factory.support.BeanDefinitionBuilder#genericBeanDefinition(java.lang.Class<?>) # 创建每个feignClient接口的代理Bean>org.springframework.beans.factory.support.BeanDefinitionReaderUtils#registerBeanDefinition # 注册到bena容器中

本文来自博客园，作者：TheLifelongLearner，转载请注明原文链接：https://www.cnblogs.com/The-Lifelong-Learner/p/20490144