POI读取主机excel文件出现io异常

情况时这样的，页面上有一个按钮，点击一下，则在内存中动态生成一个excel文件，并且让用户下载下去，让后用户可以把这个文件再传上来，问题就来了：
   如果一下载完就把这个文件上传，就会出现异常，但是不是直接下载完后上传文件就不会
异常信息如下：
      java.io.IOException: Unable to read entire block; 350 bytes read; expected 512 bytes
at org.apache.poi.poifs.storage.RawDataBlock.<init>(RawDataBlock.java:62)
at org.apache.poi.poifs.storage.RawDataBlockList.<init>(RawDataBlockList.java:51)
at org.apache.poi.poifs.filesystem.POIFSFileSystem.<init>(POIFSFileSystem.java:86)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:230)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:211)
at com.pps.mb.forMb.basedataimport.FileConverter.getWorkbook(FileConverter.java:212)
at com.pps.mb.forMb.basedataimport.FileConverter.convertXLS(FileConverter.java:75)
at com.pps.mb.forMb.basedataimport.FileUpload.convertBaseFile(FileUpload.java:67)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.myfaces.el.MethodBindingImpl.invoke(MethodBindingImpl.java:138)
at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:62)
at javax.faces.component.UICommand.broadcast(UICommand.java:106)
at javax.faces.component.UIViewRoot._broadcastForPhase(UIViewRoot.java:110)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:184)
at org.apache.myfaces.lifecycle.LifecycleImpl.invokeApplication(LifecycleImpl.java:271)
at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:102)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:109)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.myfaces.component.html.util.ExtensionsFilter.doFilter(ExtensionsFilter.java:112)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.pps.mb.ex.sysright.AuthFilter.doFilter(AuthFilter.java:185)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:595)不知道为什么后面的内容不能读取，恳请高手指教