服务器报错信息：
严重: Servlet.service() for servlet action threw exception
java.lang.NoClassDefFoundError: org/apache/commons/collections/SequencedHashMap
at org.hibernate.mapping.Table. <init> (Table.java:33)
at org.hibernate.cfg.Mappings.addTable(Mappings.java:165)
at org.hibernate.cfg.HbmBinder.bindRootPersistentClassCommonValues(HbmBinder.java:299)
at org.hibernate.cfg.HbmBinder.bindRootClass(HbmBinder.java:282)
at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:153)
at org.hibernate.cfg.Configuration.add(Configuration.java:386)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:427)
at org.hibernate.cfg.Configuration.addResource(Configuration.java:482)
at org.hibernate.cfg.Configuration.parseMappingElement(Configuration.java:1465)
at org.hibernate.cfg.Configuration.parseSessionFactory(Configuration.java:1433)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1414)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1390)
at org.hibernate.cfg.Configuration.configure(Configuration.java:1310)
at com.jihe.bangBean.SessionFactory.rebuildSessionFactory(SessionFactory.java:59)
at com.jihe.bangBean.SessionFactory.getSession(SessionFactory.java:43)
at com.jihe.bangBean.Manager. <init> (Manager.java:26)
at com.jihe.bangAction.IndexAction.execute(IndexAction.java:47)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
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:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
------解决方案--------------------
你使用了spring+hibernate框架。问题是你在导入hibernate框架的时候覆盖了之前导入的spring中的一些jar包。两个框架中有一个重复的包spring-framework-2.0.3\lib\jakarta-commons\commons-collections.jar包，在导入hibernate的时候，myeclipse会提示，你选择keepexisting。
------解决方案--------------------
ls说的在理；java.lang.NoClassDefFoundError的错误时缺少jar包造成的，有时候你还要把需要的jar包复制到服务器的lib文件夹下。
------解决方案--------------------
严重: Servlet.service() for servlet action threw exception
java.lang.NullPointerException