servlet调用普通方法会报错

[qq_31376151]

我在以前的项目中新建了个servlet dopst方法调用一个普通方法，但运行时报错
旧项目

严重: Servlet.service() for servlet AddLarger threw exception
java.lang.ClassNotFoundException: jxl.Workbook
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1647)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1493)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at com.sdmu.add.until.ExcelOperater.getExamList(ExcelOperater.java:25)
at com.sdmu.add.action.AddLarger.doPost(AddLarger.java:36)
at com.sdmu.add.action.AddLarger.doGet(AddLarger.java:27)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:864)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1600)
at java.lang.Thread.run(Thread.java:619)

但我建了一个新的web项目后却可以调用，遇到好多次了一直没搞明白，求解
新项目

[街头小贩]

少jar依赖，只要在类运行时，类路径上类依赖的jar就可以运行，没有就会出ClassNotFoundException

[qq_31376151]

当前初学web，没理解楼上的意思，明明把jar包导入项目了，却还报错。后来知道web是运行在服务器（tomcat）上的，因此WebRoot中的lib也必须导入对应的jar包