菜鸟调错——POI导出Excel报错No such file or directory

场景重现

• Apache POI
• Linux
• Tomcat

如上所示，当时在linux+tomcat的环境下，使用apache的poi导出excel的时候就会报“No such file or directory”的错误。

错误信息

java.lang.RuntimeException: java.io.IOException: No such file or directory
        at org.apache.poi.xssf.streaming.SXSSFWorkbook.createAndRegisterSXSSFSheet(SXSSFWorkbook.java:569)
        at org.apache.poi.xssf.streaming.SXSSFWorkbook.createSheet(SXSSFWorkbook.java:558)
        at com.app.util.ExcelIOUtil.write(ExcelIOUtil.java:46)
        at com.app.controllers.DrivingSchoolController.download(DrivingSchoolController.java:106)
        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:597)
        at com.mvc.invoke.ActionInvoker.invoke(ActionInvoker.java:75)
        at com.mvc.MvcDispatcher.service(MvcDispatcher.java:119)
        at com.mvc.MvcFilter.doFilter(MvcFilter.java:67)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
        at org.apache.tomcat.util.net.AprEndpoint$SocketWithOptionsProcessor.run(AprEndpoint.java:1810)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662) 

解决方案

咱们先说解决方案，因为解决的办法非常简单，只需要在tomcat的根目录下建一个“temp”的文件夹即可。

错误原因

之所以会出现这个错误，是因为poi默认将导出的excel导出到系统的临时目录，而当时那个linux的tomcat下不存在那个temp文件夹，所以就找不到目录了。其实不管是在什么系统环境下，只要tomcat根目录没有temp都会出现这个情况。看看下面poi的源码你就明白了。

    public void write(OutputStream stream) throws IOException{
	 for (SXSSFSheet sheet : _xFromSxHash.values()){
	     sheet.flushRows();
         }
        //保存到临时目录
        File tmplFile = File.createTempFile("poi-sxssf-template", ".xlsx");
        tmplFile.deleteOnExit();
        FileOutputStream os = new FileOutputStream(tmplFile);
        _wb.write(os);
        os.close();

        //Substitute the template entries with the generated sheet data files
        injectData(tmplFile, stream);
        tmplFile.delete();
    }