Java Tomcat can'；在几种情况下，由于maven的原因，无法打开

这两天，我在maven上遇到了一些问题（我是新手），所有这些都导致无法打开tomcat。以下是一些情况：

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1.导入github下载的maven项目后

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2.将动态项目更改为maven项目后

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3.在pom.xml中添加了一些依赖项之后

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4.更改与maven项目链接的数据库后

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可能还有其他情况会导致tomcat打开问题。有没有类似的情况或任何解决方案？突然间你无法打开tomcat真的很失望，可能只是做了一些事情。如果可能的话，我希望有一些解释。谢谢。 所有日志都是：

A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/WechatDemo]]
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:939)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:872)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409)
    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.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/WechatDemo]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
    ... 6 more
Caused by: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileUploadException
    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Unknown Source)
    at java.lang.Class.getDeclaredFields(Unknown Source)
    at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:110)
    at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:262)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:136)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:66)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:328)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:778)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:299)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:94)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5114)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 6 more
Caused by: java.lang.ClassNotFoundException: org.apache.commons.fileupload.FileUploadException
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1285)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1119)
    ... 19 more

七月 10, 2017 8:09:40 下午 org.apache.catalina.core.ContainerBase startInternal
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:939)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:422)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:793)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:655)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:355)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:495)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409)
    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.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:947)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:872)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 6 more

七月 10, 2017 8:09:40 下午 org.apache.catalina.startup.Catalina start
严重: The required Server component failed to start so Tomcat is unable to start.
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:655)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:355)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:495)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:793)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 7 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:422)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 9 more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:947)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 11 more

命令输出为（将my cmd中的mvn dependency:tree与项目根字典绑定后）：

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很明显，以下类别中的某些未找到：-

    org/apache/commons/fileupload/FileUploadException

必须将此库包含到项目依赖项库文件夹中

从官方网站获取“commons fileupload.jar”

从Maven存储库获取“commons fileupload.jar”

<dependency>
   <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
   <version>1.2.1</version>
 </dependency>

文件上传
文件上传
1.2.1

您需要将commons-fileupload.jar和commons-io.jar放在WEB-INF/lib文件夹中。类路径在构建期间使用，但它们也必须在运行时可用

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实际上，如果您使用IDE进行JavaEE开发（如Eclipse），将这些JAR放到WEB-INF/lib中就足够了，因为它们将在CLAPATH for build中自动可见。

打开tomcat是什么意思？启动tomcat服务？某种类型的。日志是本地主机上的tomcat v8.5服务器启动失败。不清楚。如果你有错误，请提供日志。所有的情况都有相同的例外。我已经发布了。这可能有各种原因。提供更多日志如果他还没有添加此依赖项，为什么他没有任何编译问题？可能是版本问题：）现在我知道这是类未找到的问题。但我已经将其添加到pom.xml文件中。我尝试了其他版本。我同意版本问题理论。请遵循文档

<dependency>
   <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
   <version>1.2.1</version>
 </dependency>