What class is this for?

And did you ensure you removed any (and all!) old POI jars before deploying the new ones?

Can you please provide a full stack trace? It could also be related to the problem with a really outdated XERCES in classpath.

Created attachment 31950 [details]
libs & demo

the line 36,if change Sheet to HSSFSheet, then this line will be ok.but the error move to other line.

seemingly when use interface like Sheet,Font etc the error will occur. change to HSSFSheet and HSSFFont the error disappear...

watch this:http://docs.oracle.com/javase/specs/jls/se7/html/jls-13.html
i suspect there was static method,filed or innerclass  changed ...

thanks.

Can you please post the stack trace?

[8/28/14 13:51:11:033 GMT+08:00] 00000089 servlet       E com.ibm.ws.webcontainer.servlet.ServletWrapper service SRVE0068E: Uncaught exception created in one of the service methods of the servlet /index.jsp in application demo1-1_0_0_war. Exception created : com.ibm.websphere.servlet.error.ServletErrorReport: java.lang.IncompatibleClassChangeError
	at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:695)
	at com.ibm._jsp._index._jspService(_index.java:99)
	at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:98)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
	at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1655)
	at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:937)
	at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:500)
	at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178)
	at com.ibm.wsspi.webcontainer.servlet.GenericServletWrapper.handleRequest(GenericServletWrapper.java:121)
	at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper.handleRequest(AbstractJSPExtensionServletWrapper.java:239)
	at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionProcessor.handleRequest(AbstractJSPExtensionProcessor.java:340)
	at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3826)
	at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:276)
	at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:931)
	at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1583)
	at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:186)
	at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:455)
	at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:384)
	at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:272)
	at com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.sendToDiscriminators(NewConnectionInitialReadCallback.java:214)
	at com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.complete(NewConnectionInitialReadCallback.java:113)
	at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
	at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
	at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
	at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
	at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
	at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
	at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
	at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1550)
Caused by: java.lang.IncompatibleClassChangeError
	at demo.PoiDemo.excel20031(PoiDemo.java:52)
	at demo.PoiDemo.testExcel20031(PoiDemo.java:232)
	at com.ibm._jsp._index._jspService(_index.java:88)
	... 27 more

[8/28/14 13:51:35:660 GMT+08:00] 00000089 SystemOut     O Hibernate: select count(*) as col_0_0_ from BDF2_MESSAGE message0_ where message0_.RECEIVER_=? and message0_.READ_=?
[8/28/14 13:51:35:664 GMT+08:00] 00000089 SystemOut     O Hibernate: select count(*) as y0_ from UFLO_TASK this_ where this_.ASSIGNEE_=?
[8/28/14 13:51:35:674 GMT+08:00] 00000089 SystemOut     O Hibernate: select count(*) as y0_ from UFLO_TASK this_ inner join UFLO_TASK_PARTICIPATOR taskpartic1_ on this_.ID_=taskpartic1_.TASK_ID_ where this_.STATE_=? and (taskpartic1_.USER_=?)
[8/28/14 13:51:39:070 GMT+08:00] 0000009d SystemOut     O Core POI came from file:/opt/IBM/WebSphere/PortalServer/shared/app/../../lwo/prereq.odc/shared/app/jakarta-poi.jar!/org/apache/poi/poifs/filesystem/POIFSFileSystem.class
[8/28/14 13:51:39:070 GMT+08:00] 0000009d SystemOut     O AIX
[8/28/14 13:51:39:071 GMT+08:00] 0000009d servlet       E com.ibm.ws.webcontainer.servlet.ServletWrapper service SRVE0068E: Uncaught exception created in one of the service methods of the servlet /index.jsp in application demo1-1_0_0_war. Exception created : com.ibm.websphere.servlet.error.ServletErrorReport: java.lang.IncompatibleClassChangeError
	at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:695)
	at com.ibm._jsp._index._jspService(_index.java:99)
	at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:98)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
	at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1655)
	at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:937)
	at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:500)
	at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178)
	at com.ibm.wsspi.webcontainer.servlet.GenericServletWrapper.handleRequest(GenericServletWrapper.java:121)
	at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper.handleRequest(AbstractJSPExtensionServletWrapper.java:239)
	at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3826)
	at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:276)
	at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:931)
	at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1583)
	at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:186)
	at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:455)
	at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:384)
	at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:272)
	at com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.sendToDiscriminators(NewConnectionInitialReadCallback.java:214)
	at com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.complete(NewConnectionInitialReadCallback.java:113)
	at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
	at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
	at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
	at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
	at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
	at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
	at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
	at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1550)
Caused by: java.lang.IncompatibleClassChangeError
	at demo.PoiDemo.excel20031(PoiDemo.java:52)
	at demo.PoiDemo.testExcel20031(PoiDemo.java:232)
	at com.ibm._jsp._index._jspService(_index.java:88)
	... 26 more

i known the reason,because of the the class loader policy,my libs were not loaded firstly....