在eclipse上启动tomcat后但是创建的servlet类异常，我完全按照教程写的代码啊，困扰几天了

严重: 分配异常的servlet [S1]
java.lang.ClassNotFoundException: com.unit9.s.S1
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1407)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1215)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:534)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:515)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:149)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1070)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:788)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:128)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1732)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
at org.apache.

缺少com.unit9.s.S1中S1这个servlet，看看教程，自己在你的项目于里写一个。