Java web项目Tomcat启动时发生错误，错误代码：

严重: End event threw exception
java.lang.NoSuchMethodException: org.apache.catalina.deploy.WebXml addServlet
	at org.apache.tomcat.util.IntrospectionUtils.callMethod1(IntrospectionUtils.java:849)
	at org.apache.tomcat.util.digester.SetNextRule.end(SetNextRule.java:201)
	at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:1063)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:609)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1782)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2967)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770)
	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
	at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
	at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1561)
	at org.apache.catalina.startup.ContextConfig.parseWebXml(ContextConfig.java:1812)
	at org.apache.catalina.startup.ContextConfig.getDefaultWebXmlFragment(ContextConfig.java:1467)
	at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1244)
	at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:876)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:374)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5355)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:632)
	at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1763)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:618)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:565)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:301)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
	at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
	at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
	at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
	at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:324)
	at sun.rmi.transport.Transport$1.run(Transport.java:200)
	at sun.rmi.transport.Transport$1.run(Transport.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
	at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
//后面的就省略了

out目录中的web.xml出现错误，原因就是缺少jar包

通过添加javax.servlet.jar

     <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.0-b07</version>
        </dependency>

问题成功解决