问题如下：需要使用到数据库mysql，于是将mysql-connector-java-5.1.30-bin.jar的数据库驱动复制到WEE-INF/lib目录下。点击运行，但是服务器无法启动。
控制台报错：
严重: ContainerBase.addChild: start:
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/20160925]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
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.deployDescriptor(HostConfig.java:587)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1798)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
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.NoClassDefFoundError: HttpServletRequest
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
at java.lang.Class.getDeclaredMethods(Class.java:1975)
at org.apache.catalina.util.Introspection.getDeclaredMethods(Introspection.java:127)
at org.apache.catalina.startup.WebAnnotationSet.loadMethodsAnnotation(WebAnnotationSet.java:273)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:133)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:65)
at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:336)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:786)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:307)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:95)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5213)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
... 10 more
Caused by: java.lang.ClassNotFoundException: HttpServletRequest
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1333)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1167)
... 24 more
九月 27, 2016 8:48:17 上午 org.apache.catalina.startup.HostConfig deployDescriptor
严重: Error deploying configuration descriptor E:\apache-tomcat-8.0.37\conf\Catalina\localhost\20160925.xml
java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/20160925]]
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:729)
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.deployDescriptor(HostConfig.java:587)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1798)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
解决办法：
不仅要把需要的 jar 都拷贝到 WEB-INF/lib 目录下，还要记得把Jar包 build_path ！