org.springframework.web.context.ContextLoaderListener为什么抛出ClassNotFoundException的异常？

严重: Error configuring application listener of class org.springframework.web.context.ContextLoaderListener
java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1305)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:520)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:501)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:120)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4650)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5166)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
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.deployDirectory(HostConfig.java:1096)
at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1756)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
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)

五月 08, 2015 9:50:41 下午 org.apache.catalina.core.StandardContext listenerStart
严重: Error configuring application listener of class org.springframework.web.util.IntrospectorCleanupListener
java.lang.ClassNotFoundException: org.springframework.web.util.IntrospectorCleanupListener
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1305)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:520)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:501)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:120)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4650)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5166)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
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.deployDirectory(HostConfig.java:1096)
at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1756)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
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)

 java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener  这是什么原因 我按照百度然后依依改了 jar包加了 然后在java类 里面import org.springframework.web.context.ContextLoaderListener 也可以找到 就是tomcat 启动的时候就报错 什么原因求解答