啟動時檢查的作用如下：
（1）Dubbo 缺省會在啟動時檢查依賴的服務是否可用，不可用時會拋出異常，阻止 Spring 初始化完成，以便上線時，能及早發現問題，默認 check="true"。
（2）可以通過 check="false" 關閉檢查，比如，測試時，有些服務不關心，或者出現了循環依賴，必須有一方先啟動的情況下
（3）如果你的 Spring 容器是懶加載的，或者通過 API 編程延遲引用服務，請關閉 check，否則服務臨時不可用時，會拋出異常，拿到 null 引用，如果 check="false"，總是會返回引用，當服務恢復時，能自動連上。
以前面帖子工程為例：
直接啟動服務的消費者：order-service-consumer工程，結果如下：'
具體錯誤信息如下：提示沒有提供者
1 Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'orderServiceImpl': Unsatisfied dependency expressed through field 'userService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: Failed to check the status of the service com.lch.test.service.UserService. No provider available for the service com.lch.test.service.UserService from the url zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?anyhost=true&application=order-service-consumer&check=false&dubbo=2.6.2&generic=false&interface=com.lch.test.service.UserService&methods=getUserAddressList&pid=8740®ister.ip=192.168.0.110&remote.timestamp=1563206416952&side=consumer×tamp=1563370847797 to the consumer 192.168.0.110 use dubbo version 2.6.2 2 at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) 3 at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) 4 at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) 5 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1268) 6 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) 7 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) 8 at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312) 9 at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) 10 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308) 11 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) 12 at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) 13 at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) 14 at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) 15 at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139) 16 at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83) 17 at com.lch.test.MainApplication.main(MainApplication.java:12) 18 Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: Failed to check the status of the service com.lch.test.service.UserService. No provider available for the service com.lch.test.service.UserService from the url zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?anyhost=true&application=order-service-consumer&check=false&dubbo=2.6.2&generic=false&interface=com.lch.test.service.UserService&methods=getUserAddressList&pid=8740®ister.ip=192.168.0.110&remote.timestamp=1563206416952&side=consumer×tamp=1563370847797 to the consumer 192.168.0.110 use dubbo version 2.6.2 19 at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:177) 20 at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:103) 21 at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1640) 22 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:254) 23 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) 24 at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) 25 at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1316) 26 at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1282) 27 at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1101) 28 at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) 29 at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) 30 ... 15 more 31 Caused by: java.lang.IllegalStateException: Failed to check the status of the service com.lch.test.service.UserService. No provider available for the service com.lch.test.service.UserService from the url zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?anyhost=true&application=order-service-consumer&check=false&dubbo=2.6.2&generic=false&interface=com.lch.test.service.UserService&methods=getUserAddressList&pid=8740®ister.ip=192.168.0.110&remote.timestamp=1563206416952&side=consumer×tamp=1563370847797 to the consumer 192.168.0.110 use dubbo version 2.6.2 32 at com.alibaba.dubbo.config.ReferenceConfig.createProxy(ReferenceConfig.java:422) 33 at com.alibaba.dubbo.config.ReferenceConfig.init(ReferenceConfig.java:333) 34 at com.alibaba.dubbo.config.ReferenceConfig.get(ReferenceConfig.java:163) 35 at com.alibaba.dubbo.config.spring.ReferenceBean.getObject(ReferenceBean.java:66) 36 at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:170) 37 ... 25 more
這是因為，如果沒有配置啟動檢查，dubbo是默認進行啟動檢查的，也就是啟動服務的消費者時，先檢查服務的提供者有沒有啟動起來。
修改配置文件,在dubboLreference標簽里面加上 check=“false”
1 <?xml version="1.0" encoding="UTF-8"?> 2 <beans xmlns="http://www.springframework.org/schema/beans" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xmlns:dubbo="http://dubbo.apache.org/schema/dubbo" 5 xmlns:context="http://www.springframework.org/schema/context" 6 xsi:schemaLocation="http://www.springframework.org/schema/beans 7 http://www.springframework.org/schema/beans/spring-beans-4.3.xsd 8 http://dubbo.apache.org/schema/dubbo 9 http://dubbo.apache.org/schema/dubbo/dubbo.xsd 10 http://www.springframework.org/schema/context 11 http://www.springframework.org/schema/context/spring-context.xsd"> 12 13 <!--掃描包注解 --> 14 <context:component-scan 15 base-package="com.lch.test.service.impl" /> 16 17 <!-- 1.消費方應用名 --> 18 <dubbo:application name="order-service-consumer" /> 19 20 <!-- 2.指定注冊中心地址 --> 21 <dubbo:registry address="zookeeper://127.0.0.1:2181" /> 22 23 <!-- 生成遠程服務代理dubbo:reference：聲明需要調用的遠程服務的接口 --> 24 <!-- user-service-provider工程里面暴露了一個名為userService的服務，這里要引用這個服務 --> 25 <dubbo:reference id="userService" 26 interface="com.lch.test.service.UserService" check="false"/> 27 28 <!-- 連接監控中心：使用自動發現的方式 --> 29 <dubbo:monitor protocol="register" /> 30 <!-- 直連注冊中心 --> 31 <!-- <dubbo:monitor address="127.0.0.1:7070" /> --> 32 33 34 </beans>
然后再啟動服務的消費者：
dubbo啟動時檢查可以配置三種作用范圍,上面例子是僅僅關閉對user-service-provider這個服務提供者的檢查，如果要關閉所有服務消費者對 與其對應的服務提供者的檢查，
可以在標簽 dubbo:consumer 中添加check="false" 即： <dubbo:consumer check="false" />
