开门见山

对着Dubbo官网玩，并使用ZooKeeper作为注册中心，在使用Maven 导入包时要注意了，我导入的 dubbo 版本是2.6.5（github中的），在Dubbo官方中的ZooKeeper的curator 客户端给出的依赖版本是1.1.10，加入依赖并启动服务提供者，就开启报错模式了

报错原因

在一番折腾后，发现问题就出在curator这个依赖中，版本号太低了，到Maven 仓库中找新一版的。

<!-- Dubbo 官网介绍ZooKeeper作为注册中心给出的 curator 版本 -->
<dependency>
    <groupId>com.netflix.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>1.1.10</version>
</dependency>

解决方案

Dubbo最新稳定版都 2.6.5 了， curator 才 1.1.10，这么低的版本不报错都没理由了，赶紧换个最新 4.0.1版本，再启动服务提供者，完美解决报错

<!-- 修改后的 curator 依赖 -->
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>4.0.1</version>
</dependency>

报错代码

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/curator/RetryPolicy
	at com.alibaba.dubbo.remoting.zookeeper.curator.CuratorZookeeperTransporter.connect(CuratorZookeeperTransporter.java:27)
	at com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter$Adaptive.connect(ZookeeperTransporter$Adaptive.java)
	at com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistry.<init>(ZookeeperRegistry.java:69)
	at com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistryFactory.createRegistry(ZookeeperRegistryFactory.java:38)
	at com.alibaba.dubbo.registry.support.AbstractRegistryFactory.getRegistry(AbstractRegistryFactory.java:96)
	at com.alibaba.dubbo.registry.RegistryFactory$Adaptive.getRegistry(RegistryFactory$Adaptive.java)
	at com.alibaba.dubbo.registry.integration.RegistryProtocol.getRegistry(RegistryProtocol.java:203)
	at com.alibaba.dubbo.registry.integration.RegistryProtocol.export(RegistryProtocol.java:137)
	at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper.export(ProtocolFilterWrapper.java:98)
	at com.alibaba.dubbo.rpc.protocol.ProtocolListenerWrapper.export(ProtocolListenerWrapper.java:55)
	at com.alibaba.dubbo.qos.protocol.QosProtocolWrapper.export(QosProtocolWrapper.java:60)
	at com.alibaba.dubbo.rpc.Protocol$Adaptive.export(Protocol$Adaptive.java)
	at com.alibaba.dubbo.config.ServiceConfig.doExportUrlsFor1Protocol(ServiceConfig.java:513)
	at com.alibaba.dubbo.config.ServiceConfig.doExportUrls(ServiceConfig.java:358)
	at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:317)
	at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:216)
	at com.alibaba.dubbo.config.spring.ServiceBean.export(ServiceBean.java:291)
	at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:131)
	at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:53)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:393)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:347)
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:883)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at com.zlk.start.Provider.main(Provider.java:10)
Caused by: java.lang.ClassNotFoundException: org.apache.curator.RetryPolicy
	at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 29 more