title: Error when parsing an embedded .xlsx file from a .ppt using apache-poi. The supplied POIFSFileSystem does not contain a BIFF8 'Workbook' entry
body: <p>I am facing an issue when using apache poi to extract an embedded .xlsx files from a .ppt file. It would be really great if somebody could help me out.</p>
  <p>The subject of the problem:</p>
  <p>Problem trying to solve: Extracting a &quot;.xlsx&quot; file embedded inside a &quot;.ppt&quot;.</p>
  <p>I am currently using apache-poi.</p>
  <p>It seems that when I try to do it using hslfSlideShow.getEmbeddedObjects(), I get the xlsx object just fine but when I try converting it to the XLSFWorkbook object using say WorkbookFactory.create(inputStream), it threw an error saying</p>
  <pre><code>java.lang.IllegalArgumentException: The supplied POIFSFileSystem does not contain a BIFF8 'Workbook' entry. Is it really an excel file? Had: [OlePres000, Ole, CompObj, Package]
  at org.apache.poi.hssf.usermodel.HSSFWorkbook.getWorkbookDirEntryName(HSSFWorkbook.java:286)
  at org.apache.poi.hssf.usermodel.HSSFWorkbook.&lt;init&gt;(HSSFWorkbook.java:326)
  at org.apache.poi.hssf.usermodel.HSSFWorkbookFactory.createWorkbook(HSSFWorkbookFactory.java:64)
  at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:167)
  at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:112)
  at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:253)
  at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:221)
  </code></pre>
  <p>Interestingly it is calling HSSFWorkbookFactory even though its an xlsx file.</p>
  <p>And <strong>no the xlsx file is not corrupted/password-protected</strong>. I can open it just fine.</p>
  <p>Also, it works <strong>fine</strong> if I try parsing the .xlsx file <strong>without</strong> embedding it in the .ppt.</p>
  <p>And the parsing works fine when I embed it in a .pptx file and call methods such as xmlSlideShow.getAllEmbeddedParts() to get the embedded objects from .pptx.</p>