title: Read xlsx file using POIFSFileSystem
body: <p>I need to unprotect a protected xlsx file.e.g Book1.xlsx 
  Below code runs fine for the first time, Reads Book1.xlsx, decrypt it and again write it to the same filename. </p>
  
  <pre><code>public static void unprotectXLSXSheet(String fileName, String password) {
          try{
  
              POIFSFileSystem fs = new POIFSFileSystem(new FileInputStream(fileName));
              EncryptionInfo info = new EncryptionInfo(fs);
              Decryptor d = Decryptor.getInstance(info);
              d.verifyPassword(password);
              InputStream is = d.getDataStream(fs);
              System.out.println(is.available());
              XSSFWorkbook wb = new XSSFWorkbook(OPCPackage.open(is));
              FileOutputStream fileOut;
              fileOut = new FileOutputStream(fileName);
              wb.write(fileOut);
               fileOut.flush();
              fileOut.close();
              }catch(FileNotFoundException ex){
                  ex.printStackTrace();
              }catch(IOException ex){
                  ex.printStackTrace();
  </code></pre>
  
  <p>But when the same code tries to access the newly created unprotected Book1.xlsx(or anyother unprotected xlsx file) it fails and showing </p>
  
  <pre><code>Exception in thread "main" org.apache.poi.poifs.filesystem.OfficeXmlFileException: The supplied data appears to be in the Office 2007+ XML. You are calling the part of POI that deals with OLE2 Office Documents. You need to call a different part of POI to process this data (eg XSSF instead of HSSF)
      at org.apache.poi.poifs.storage.HeaderBlock.&lt;init&gt;(HeaderBlock.java:131)
      at org.apache.poi.poifs.storage.HeaderBlock.&lt;init&gt;(HeaderBlock.java:104)
      at org.apache.poi.poifs.filesystem.POIFSFileSystem.&lt;init&gt;(POIFSFileSystem.java:138)
      at com.wolseley.Excel.TestMainDummy.unprotectXLSXSheet(TestMainDummy.java:113)
      at com.wolseley.Excel.TestMainDummy.main(TestMainDummy.java:52)
  </code></pre>
  
  <p>i need help in reading xlsx file and also unlock it using password, as done above.</p>