在启动时报如下异常：
ERROR [nacos.publisher-com.alibaba.nacos.client.naming.event.InstancesChangeEvent] [TRACEID:] [c.a.n.c.n.NotifyCenter:208]}: Event callback exception:
java.lang.NullPointerException: null
at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1693) ~[?:?]
at org.apache.dubbo.registry.client.DefaultServiceInstance.toURL(DefaultServiceInstance.java:294) ~[dubbo-3.2.11.jar!/:3.2.11]
at org.apache.dubbo.registry.client.event.listener.ServiceInstancesChangedListener.getServiceUrlsCache(ServiceInstancesChangedListener.java:407) ~[dubbo-3.2.11.jar!/:3.2.11]
at org.apache.dubbo.registry.client.event.listener.ServiceInstancesChangedListener.lambda$doOnEvent$5(ServiceInstancesChangedListener.java:234) ~[dubbo-3.2.11.jar!/:3.2.11]
at java.util.HashMap.computeIfAbsent(HashMap.java:1220) ~[?:?]
at org.apache.dubbo.registry.client.event.listener.ServiceInstancesChangedListener.doOnEvent(ServiceInstancesChangedListener.java:232) ~[dubbo-3.2.11.jar!/:3.2.11]
at org.apache.dubbo.registry.client.event.listener.ServiceInstancesChangedListener.onEvent(ServiceInstance
发生此问题的主要原因是在~/.dubbo/目录下存在dubbo的元数据缓存文件（.metadata开头），把此文件夹下相关文件删除即可
