IDEA启动Tomcat，报“LifecycleException: Failed to start component [StandardEngine[Catalina]

        IDEA启动Tomcat，报“LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]”问题。

        1、 IDEA启动Tomcat，报下面的错误：

org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:158)at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:724)at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:700)at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1702)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:300)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:482)at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:431)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:300)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:323)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)Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> firstServlet.do in servlet mappingat org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3128)at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3103)at org.apache.catalina.startup.ContextConfig.configureContext(ContextConfig.java:1367)at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1181)at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:771)at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:298)at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:94)at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5076)at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:152)

        2、解决方案：发现是web.xml配置“servlet-mapping”的“url-pattern”少了斜杠；增加斜杠即可。