问题现象

dubbo服务的生产者启动失败报错：

 .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.4.RELEASE)

[06/10/19 07:36:26:026 CST] main  INFO provider.ProviderApplication: Starting ProviderApplication on geektcp-PC with PID 8180 (D:\alpha\alpha-dubbo\alpha-dubbo-provider\target\classes started by Administrator in D:\alpha)
[06/10/19 07:36:26:026 CST] main  INFO provider.ProviderApplication: No active profile set, falling back to default profiles: default
[06/10/19 07:36:26:026 CST] main  INFO annotation.AnnotationConfigApplicationContext: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@61d6015a: startup date [Sun Oct 06 19:36:26 CST 2019]; root of context hierarchy
[06/10/19 07:36:26:026 CST] main  INFO logger.LoggerFactory: using logger: com.alibaba.dubbo.common.logger.log4j.Log4jLoggerAdapter
[06/10/19 07:36:26:026 CST] main  INFO annotation.ServiceAnnotationBeanPostProcessor:  [DUBBO] BeanNameGenerator bean can't be found in BeanFactory with name [org.springframework.context.annotation.internalConfigurationBeanNameGenerator], dubbo version: 2.6.2, current host: 192.168.1.200
[06/10/19 07:36:26:026 CST] main  INFO annotation.ServiceAnnotationBeanPostProcessor:  [DUBBO] BeanNameGenerator will be a instance of org.springframework.context.annotation.AnnotationBeanNameGenerator , it maybe a potential problem on bean name generation., dubbo version: 2.6.2, current host: 192.168.1.200
[06/10/19 07:36:26:026 CST] main  WARN annotation.ServiceAnnotationBeanPostProcessor:  [DUBBO] The BeanDefinition[Root bean: class [com.alibaba.dubbo.config.spring.ServiceBean]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null] of ServiceBean has been registered with name : ServiceBean:demoServiceImpl:com.geektcp.alpha.dubbo.api.DemoService, dubbo version: 2.6.2, current host: 192.168.1.200
[06/10/19 07:36:26:026 CST] main  INFO annotation.ServiceAnnotationBeanPostProcessor:  [DUBBO] 1 annotated Dubbo's @Service Components { [Bean definition with name 'demoServiceImpl': Generic bean: class [com.geektcp.alpha.dubbo.provider.service.DemoServiceImpl]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in file [D:\alpha\alpha-dubbo\alpha-dubbo-provider\target\classes\com\geektcp\alpha\dubbo\provider\service\DemoServiceImpl.class]] } were scanned under package[com.geektcp.alpha.dubbo.provider.service], dubbo version: 2.6.2, current host: 192.168.1.200
[06/10/19 07:36:27:027 CST] main  WARN annotation.AnnotationConfigApplicationContext: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration': Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'spring.info-org.springframework.boot.autoconfigure.info.ProjectInfoProperties': Initialization of bean failed; nested exception is javax.validation.ValidationException: Unable to create a Configuration, because no Bean Validation provider could be found. Add a provider like Hibernate Validator (RI) to your classpath.
[06/10/19 07:36:27:027 CST] main  INFO annotation.AnnotationMBeanExporter: Unregistering JMX-exposed beans on shutdown
[06/10/19 07:36:27:027 CST] main  INFO annotation.ReferenceAnnotationBeanPostProcessor: class com.alibaba.dubbo.config.spring.beans.factory.annotation.ReferenceAnnotationBeanPostProcessor was destroying!
[06/10/19 07:36:27:027 CST] main  INFO logging.AutoConfigurationReportLoggingInitializer: 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
[06/10/19 07:36:27:027 CST] main ERROR diagnostics.LoggingFailureAnalysisReporter: 

***************************
APPLICATION FAILED TO START
***************************

Description:

The Bean Validation API is on the classpath but no implementation could be found

Action:

Add an implementation, such as Hibernate Validator, to the classpath

[06/10/19 07:36:27:027 CST] DubboShutdownHook  INFO config.AbstractConfig:  [DUBBO] Run shutdown hook now., dubbo version: 2.6.2, current host: 192.168.1.200
[06/10/19 07:36:27:027 CST] DubboShutdownHook  INFO support.AbstractRegistryFactory:  [DUBBO] Close all registries [], dubbo version: 2.6.2, current host: 192.168.1.200

　解决方案

这个问题原因看起来是跟Validate有关，但是添加如下依赖，问题不会解决：

 <dependency>
　　<groupId>org.hibernate</groupId>
　　<artifactId>hibernate-validator</artifactId>
　　<version>5.3.0.Final</version>
</dependency>

　　

真正是解决办法，添加如下依赖：

<dependency>
　　<groupId>org.springframework.boot</groupId>
　　<artifactId>spring-boot-starter-web</artifactId>
　　<version>1.5.4.RELEASE</version>
</dependency>

通常带有版本依赖的项目，子模块不需要指定版本，那么添加如下依赖即可：

<dependency>
　　<groupId>org.springframework.boot</groupId>
　　<artifactId>spring-boot-starter-web</artifactId>
</dependency>

　　

原因分析

没有spring-boot-starter-web的这个依赖，代码也不会有报错，但是dubbo内部需要用到web服务，所以要有这个依赖。

但是加了这个依赖，使用dubbo开发的springboot项目的日志就不是很好打印了，因为老是有一个警告在启动日志的开头，如下：

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/F:/mavenLocalRepository/ch/qos/logback/logback-classic/1.1.11/logback-classic-1.1.11.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/F:/mavenLocalRepository/org/slf4j/slf4j-log4j12/1.7.25/slf4j-log4j12-1.7.25.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.4.RELEASE)