首先我的项目结构是这样的：
作为一个简单的Demo项目，启动时报错：
No application config found or it’s not a valid config! Please add <dubbo:application name=“…” />
可是配置添加了
application.properties ```java # 服务器端口号设为8082 server.port=8082 # 应用程序名称设为actuator spring.application.name=actuator # Dubbo注册中心地址 dubbo.registry.address=zookeeper://192.168.122.128:2181 # Dubbo协议名称 dubbo.protocol.name=dubbo # Dubbo协议端口号 dubbo.protocol.port=-1 # Dubbo注册中心连接超时时间 dubbo.registry.timeout=60000 # Dubbo服务消费者重试次数 dubbo.consumer.retries=3 # Dubbo应用程序QoS（Quality of Service）开启 dubbo.application.qos.enable=true # Dubbo QoS（Quality of Service）协议端口号 dubbo.qos.port=22222
通过搜索引擎尝试：原来项目的dubbo版本是3.0.0，修改为以下
1.jdk1.8+dubbo版本是2.7.5版本是没有问题 2.jdk11+dubbo版本是2.7.1版本是没有问题的
然后报错：
Description: The bean 'dubboBootstrapApplicationListener' could not be registered. A bean with that name has already been defined and overriding is disabled. Action: Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true
添加配置：spring.main.allow-bean-definition-overriding=true，启动类上添加注解@EnableDubbo
然后报错：
java.lang.IllegalStateException: zookeeper not connected at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.<init>(CuratorZookeeperClient.java:83) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperTransporter.createZookeeperClient(CuratorZookeeperTransporter.java:26) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.remoting.zookeeper.support.AbstractZookeeperTransporter.connect(AbstractZookeeperTransporter.java:68) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.remoting.zookeeper.ZookeeperTransporter$Adaptive.connect(ZookeeperTransporter$Adaptive.java) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.configcenter.support.zookeeper.ZookeeperDynamicConfiguration.<init>(ZookeeperDynamicConfiguration.java:70) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.configcenter.support.zookeeper.ZookeeperDynamicConfigurationFactory.createDynamicConfiguration(ZookeeperDynamicConfigurationFactory.java:37) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.lambda$getDynamicConfiguration$0(AbstractDynamicConfigurationFactory.java:39) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory$$Lambda$565/918738473.apply(Unknown Source) ~[na:na] at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1660) ~[na:1.8.0_51] at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.getDynamicConfiguration(AbstractDynamicConfigurationFactory.java:39) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.common.config.configcenter.DynamicConfiguration.getDynamicConfiguration(DynamicConfiguration.java:223) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.prepareEnvironment(DubboBootstrap.java:815) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.startConfigCenter(DubboBootstrap.java:560) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.useRegistryAsConfigCenterIfNecessary(DubboBootstrap.java:624) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.initialize(DubboBootstrap.java:508) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.start(DubboBootstrap.java:698) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextRefreshedEvent(DubboBootstrapApplicationListener.java:52) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:45) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40) ~[dubbo-2.7.5.jar:2.7.5] at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:404) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:361) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:898) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:554) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:755) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:402) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1247) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1236) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at com.example.dubboactuator.DubboActuatorApplication.main(DubboActuatorApplication.java:16) [classes/:na] Caused by: java.lang.IllegalStateException: zookeeper not connected at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.<init>(CuratorZookeeperClient.java:80) ~[dubbo-2.7.5.jar:2.7.5] ... 33 common frames omitted 2023-07-28 22:19:03.204 WARN 15832 --- [ main] ConfigServletWebServerApplicationContext : Exception thrown from ApplicationListener handling ContextClosedEvent java.lang.NullPointerException: null at org.apache.dubbo.config.bootstrap.DubboBootstrap.unexportMetadataService(DubboBootstrap.java:857) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.destroy(DubboBootstrap.java:996) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.stop(DubboBootstrap.java:776) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextClosedEvent(DubboBootstrapApplicationListener.java:56) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:47) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40) ~[dubbo-2.7.5.jar:2.7.5] at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:404) [spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:361) [spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1013) [spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.doClose(ServletWebServerApplicationContext.java:170) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.context.support.AbstractApplicationContext.close(AbstractApplicationContext.java:979) [spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:811) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:322) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1247) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1236) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at com.example.dubboactuator.DubboActuatorApplication.main(DubboActuatorApplication.java:16) [classes/:na] 2023-07-28 22:19:03.205 INFO 15832 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor' 2023-07-28 22:19:03.205 INFO 15832 --- [ main] f.a.ReferenceAnnotationBeanPostProcessor : class org.apache.dubbo.config.spring.beans.factory.annotation.ReferenceAnnotationBeanPostProcessor was destroying! Disconnected from the target VM, address: '127.0.0.1:53183', transport: 'socket' Process finished with exit code 1
通过另一个项目测试zookeeper可以正常访问，说明不是zookeeper的问题，那么还是回归到代码本身，推测要么是配置不对，要么是版本有冲突或者不支持。而根据后续日志分析：
java.lang.NullPointerException: null at org.apache.dubbo.config.bootstrap.DubboBootstrap.unexportMetadataService(DubboBootstrap.java:857) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.destroy(DubboBootstrap.java:996) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.bootstrap.DubboBootstrap.stop(DubboBootstrap.java:776) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextClosedEvent(DubboBootstrapApplicationListener.java:56) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:47) ~[dubbo-2.7.5.jar:2.7.5] at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40) ~[dubbo-2.7.5.jar:2.7.5]
有一个对null对象的引用，而不应该有null对象，特别是在“DubboBootstrap”类中，当取消扩展元数据服务时。可以看到unexportMetadataService()方法中存在空指针异常，可能是由于元数据服务未正确导出或其他原因导致的。这可能是由应用程序中的编码错误或Dubbo框架的配置问题引起的。
尝试使用Dubbo 2.7.6，因为从Dubbo 2.7.6开始，有关元数据服务的处理已经得到了改进。
然后又报错：
java.lang.IllegalStateException: Invalid name="org.apache.dubbo.config.ApplicationConfig#0" contains illegal character, only digit, letter, '-', '_' or '.' is legal. at org.apache.dubbo.config.utils.ConfigValidationUtils.checkProperty(ConfigValidationUtils.java:588) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.utils.ConfigValidationUtils.checkName(ConfigValidationUtils.java:546) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.utils.ConfigValidationUtils.validateApplicationConfig(ConfigValidationUtils.java:386) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.bootstrap.DubboBootstrap.checkGlobalConfigs(DubboBootstrap.java:526) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.bootstrap.DubboBootstrap.initialize(DubboBootstrap.java:513) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.bootstrap.DubboBootstrap.start(DubboBootstrap.java:740) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextRefreshedEvent(DubboBootstrapApplicationListener.java:59) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:52) ~[dubbo-2.7.6.jar:2.7.6] at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40) ~[dubbo-2.7.6.jar:2.7.6] at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:404) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:361) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:898) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:554) ~[spring-context-5.2.15.RELEASE.jar:5.2.15.RELEASE] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:755) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:402) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1247) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1236) [spring-boot-2.3.12.RELEASE.jar:2.3.12.RELEASE] at com.example.dubboactuator.DubboActuatorApplication.main(DubboActuatorApplication.java:16) [classes/:na] 2023-07-28 22:48:25.086 INFO 18636 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor' 2023-07-28 22:48:25.086 INFO 18636 --- [ main] f.a.ReferenceAnnotationBeanPostProcessor : class org.apache.dubbo.config.spring.beans.factory.annotation.ReferenceAnnotationBeanPostProcessor was destroying! Disconnected from the target VM, address: '127.0.0.1:54870', transport: 'socket' Process finished with exit code 1
添加配置：
dubbo.application.name=actuator
启动就不报错了
