问题
今天部署servlet是报下面错误
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/news]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1017)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:993)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1899)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
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:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
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:1487)
at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:97)
at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1328)
at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1420)
at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:848)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
at sun.rmi.transport.Transport$2.run(Transport.java:202)
at sun.rmi.transport.Transport$2.run(Transport.java:199)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:198)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:567)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:828)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.access$400(TCPTransport.java:619)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$1.run(TCPTransport.java:684)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$1.run(TCPTransport.java:681)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:681)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)解决
开发环境为idea2018，Tomcat 7，maven3，开始查到的问题是web.xml的头配置文件版本太低，改为下面的配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">问题还是没解决，最后看配置servlet-mapping中的url-pattern 配置中少写了 / 最终问题解决
总结
错误原因：
1 servlet servlet-name servlet-class servlet-mapping url-pattern 拼写有误
2 servlet-class路径有问题
3 url-pattern缺少/
4 idea中maven创建的webapp项目web.xml 头文件配置版本较低