web.xm里配置Listener报java.lang.ClassNotFoundException:

    <listener>
         <description>在线用户监听器</description>
         <listener-class>com.leruan.aasimp.listener.OnLineListener</listener-class>
    </listener>

 上面是监听器的配置，com.leruan.aasimp.listener.OnLineListener我的项目里是有的，但是启动tomcat时报如下错误：

java.lang.ClassNotFoundException: com.leruan.aasimp.listener.OnLineListener
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3877)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4429)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:526)
    at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:987)
    at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:909)
    at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:495)
    at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1206)
    at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:314)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:722)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:516)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)

 深夜了，不知道还有人没，实在捉急啊，有点头大。。。