问题：springboot在使用spring-boot-starter-mail发送邮件，你可能遇到以下情况：
在idea运行正常，打包成tomcat运行项目后缺突然报错的问题，错误描述如下：
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'baseController': Unsatisfied dependency expressed through field 'emailService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'emailService': Lookup method resolution failed; nested exception is java.lang.IllegalStateException: Failed to introspect Class [com.xinwei.service.EmailService] from ClassLoader [WebappClassLoader
context: demo_war_exploded
delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@5b2133b1
]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:587)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:91)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:373)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1350)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:580)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:503)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:395)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:327)
at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.run(SpringBootServletInitializer.java:155)
at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.createRootApplicationContext(SpringBootServletInitializer.java:135)
at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.onStartup(SpringBootServletInitializer.java:87)
at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:172)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5170)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1101)
at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1816)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'emailService': Lookup method resolution failed; nested exception is java.lang.IllegalStateException: Failed to introspect Class [com.xinwei.service.EmailService] from ClassLoader [WebappClassLoader
context: demo_war_exploded
delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@5b2133b1
]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:262)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:1204)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1129)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:503)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:251)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1065)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:584)
... 32 common frames omitted
Caused by: java.lang.IllegalStateException: Failed to introspect Class [com.xinwei.service.EmailService] from ClassLoader [WebappClassLoader
context: demo_war_exploded
delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@5b2133b1
]
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:659)
at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:556)
at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:541)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:245)
... 44 common frames omitted
Caused by: java.lang.NoClassDefFoundError: javax/mail/MessagingException
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
at java.lang.Class.getDeclaredMethods(Unknown Source)
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:641)
... 47 common frames omitted
Caused by: java.lang.ClassNotFoundException: javax.mail.MessagingException
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1333)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1167)
... 51 common frames omitted
通过错误描述我们发现java.lang.NoClassDefFoundError: javax/mail/MessagingException，主要说找不到这个类。通过查询发现是缺少javax.mail-api-1.6.2.jar和activation-1.1.1.jar包。在maven上下载即可，同时你还需要注意和这两个包和tomcat版本匹配问题。