前言

gateway可以默认通过配置开启，服务自动注册服务名为网关路由地址，比如：服务sc-xxx，可以通过：http://gateway/sc-xx/** 进行访问，开启对应的配置如下：

spring:
  cloud:
    gateway:
      routes:
        discovery:
          locator:
            enabled: true

但有时候我们不想这个样做，原因：

• 开启默认的服务名方式路由映射，会将所有服务的路径都自动暴露在网关下。
• 微服务体系中有多个网关，路由不同的服务，不能默认所有服务都进行路由配置。
• 有时候需要对网关进行额外的配置，比如做个反向代理、转发服务名改为其他名称，默认locator无法满足
• 修改网关配置，需要重启服务，有没有可以不重新打包，不重启就能设置网关配置项的方式哪？

动态网关解决的问题

• 解决修改路由信息和网关服务配置信息必须重启服务才能生效
• 网关作为服务入口，避免重启，造成服务不稳定

实现思路

• 路由信息、配置信息放在nacos中，gateway项目监听nacos对应的配置修改
• 基于SpringCloud Gateway的 RouteDefinitionWriter 接口删除和新增路由配置
• 基于事件 RefreshRoutesEvent 刷新系统中的路由配置

实现细节

新建一个动态路由操作类 DynamicRouteManager 因为要发布 RefreshRoutesEvent 事件，所以需要实现spring 的 ApplicationEventPublisherAware 接口，提供如下方法：

• 增加路由 void add(RouteDefinition definition)
• 更新路由 void update(RouteDefinition definition)
• 删除路由 void delete(String id)

import org.springframework.cloud.gateway.event.RefreshRoutesEvent;
import org.springframework.cloud.gateway.route.RouteDefinition;
import org.springframework.cloud.gateway.route.RouteDefinitionWriter;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.stereotype.Component;
import reactor.core.publisher.Mono;

import java.util.List;

/**
 * 动态路由OP类
 */
@Component
public class DynamicRouteManager implements ApplicationEventPublisherAware {

	private final RouteDefinitionWriter routeDefinitionWriter;

	private ApplicationEventPublisher publisher;

	public DynamicRouteManager(RouteDefinitionWriter routeDefinitionWriter) {
		this.routeDefinitionWriter = routeDefinitionWriter;
	}

	@Override
	public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
		this.publisher = applicationEventPublisher;
	}

	/**
	 * 增加路由
	 */
	public void add(RouteDefinition definition) {
                routeDefinitionWriter.save(Mono.just(definition)).subscribe();
                publisher.publishEvent(new RefreshRoutesEvent(this));
	}

	/**
	 * 更新路由
	 */
	public void update(RouteDefinition definition) {
                routeDefinitionWriter.delete(Mono.just(definition.getId()));
		routeDefinitionWriter.save(Mono.just(definition)).subscribe();
		publisher.publishEvent(new RefreshRoutesEvent(this));
	}

	/**
	 * 批量更新路由
	 */
	public void updateList(List<RouteDefinition> routeDefinitions) {
		routeDefinitions.forEach(this::update);
	}

	/**
	 * 删除路由
	 */
	public void delete(String id) {
		routeDefinitionWriter.delete(Mono.just(id));
	}


}

新建一个 NacosDynamicRouteListener 监听类nacos路由信息变化

import com.alibaba.cloud.nacos.NacosConfigProperties;
import com.alibaba.cloud.nacos.NacosDiscoveryProperties;
import com.alibaba.fastjson.JSON;
import com.alibaba.nacos.api.NacosFactory;
import com.alibaba.nacos.api.PropertyKeyConst;
import com.alibaba.nacos.api.config.ConfigService;
import com.alibaba.nacos.api.config.listener.Listener;
import com.alibaba.nacos.api.exception.NacosException;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.cloud.gateway.route.RouteDefinition;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.Properties;
import java.util.concurrent.Executor;

/**
 * 动态路由监听器
 *
 * @author Chill
 */
@Order
@Slf4j
@Component
public class NacosDynamicRouteListener implements InitializingBean {

	private final DynamicRouteManager dynamicRouteManager;
	private final NacosDiscoveryProperties nacosDiscoveryProperties;
	private final NacosConfigProperties nacosConfigProperties;
	private final DynamicRouteProperties dynamicRouteProperties;

	public NacosDynamicRouteListener(DynamicRouteManager dynamicRouteManager,
									 NacosDiscoveryProperties nacosDiscoveryProperties,
									 NacosConfigProperties nacosConfigProperties,
									 DynamicRouteProperties dynamicRouteProperties) {
		this.dynamicRouteManager = dynamicRouteManager;
		this.nacosDiscoveryProperties = nacosDiscoveryProperties;
		this.nacosConfigProperties = nacosConfigProperties;
		this.dynamicRouteProperties = dynamicRouteProperties;
	}

	/**
	 * 监听Nacos的动态路由配置
	 */
	private void dynamicRouteListener() {
		try {
			String dataId = dynamicRouteProperties.getDataId();
			String group = nacosConfigProperties.getGroup();
			Properties properties = new Properties();
			properties.setProperty(PropertyKeyConst.NAMESPACE, nacosDiscoveryProperties.getNamespace());
			properties.setProperty(PropertyKeyConst.SERVER_ADDR, nacosDiscoveryProperties.getServerAddr());
			ConfigService configService = NacosFactory.createConfigService(properties);
			configService.addListener(dataId, group, new Listener() {
				@Override
				public void receiveConfigInfo(String configInfo) {
					log.info("---监听到路由信息刷新---\n{}\n---------------------------------------", configInfo);
					List<RouteDefinition> routeDefinitions = JSON.parseArray(configInfo, RouteDefinition.class);
					dynamicRouteManager.updateList(routeDefinitions);
				}

				@Override
				public Executor getExecutor() {
					return null;
				}
			});
			String configInfo = configService.getConfig(dataId, group, 1000 * 10);
			if (configInfo != null) {
				List<RouteDefinition> routeDefinitions = JSON.parseArray(configInfo, RouteDefinition.class);
				dynamicRouteManager.updateList(routeDefinitions);
			}
		} catch (NacosException e) {
			log.error("动态路由监听异常", e);
		}
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		dynamicRouteListener();
	}
}

实例展示

监听路由配置信息：xxx.xxx.xxx.json 配置文件，初始配置如下：

[
    {
        "id":"service-xxx",
        "uri":"lb://service-xxx/",
        "predicates":[
            {
                "name":"Path",
                "args":{
                    "pattern1":"/service-xxx/**"
                }
            }
        ],
        "order":1
    }
]

访问地址：http://localhost:8000/service-xxx ，响应结果报错500说明服务路由识别成功，并没有404，可以用一个正常的接口测试就不会500了。

{
    "msg": "Failed to handle request [GET http://localhost:8002/service-xxx]: ",
    "code": 500,
    "data": null
}

修改一下Naco对应json配置,pattern1的service-xxx1 改成 service-xxx1/如下：

[
    {
        "id":"service-xxx",
        "uri":"lb://service-xxx/",
        "predicates":[
            {
                "name":"Path",
                "args":{
                    "pattern1":"/service-xxx1/**"
                }
            }
        ],
        "order":1
    }
]

日志打印：

2022-06-20 18:24:14.362 [xxx-gateway]  INFO 509450 [ternal.notifier] o.s.v.g.d.NacosDynamicRouteListener      76   [TID: N/A] : ---监听到路由信息刷新---
[
    {
        "id":"service-xxx",
        "uri":"lb://service-xxx/",
        "predicates":[
            {
                "name":"Path",
                "args":{
                    "pattern1":"/service-xxx1/**"
                }
            }
        ],
        "order":1
    }
]

再次访问原接口：http://localhost:8000/service-xxx ，404 报错，路由信息已经改变了。

{
    "msg": "Failed to handle request [GET http://localhost:8002/service-xxx]: 404 NOT_FOUND",
    "code": 404,
    "data": null
}