title: How to open .xlsx files with POI SS?
body: <p>I am trying to open .xlsx files with POI SS with this code (taken from <a href="http://poi.apache.org/spreadsheet/quick-guide.html#ReadWriteWorkbook" rel="nofollow">http://poi.apache.org/spreadsheet/quick-guide.html#ReadWriteWorkbook</a>):</p>
  
  <pre><code>InputStream inp = new FileInputStream("workbook.xls");
  //InputStream inp = new FileInputStream("workbook.xlsx");
  
  Workbook wb = WorkbookFactory.create(inp);
  Sheet sheet = wb.getSheetAt(0);
  Row row = sheet.getRow(2);
  Cell cell = row.getCell(3);
  if (cell == null)
      cell = row.createCell(3);
  cell.setCellType(Cell.CELL_TYPE_STRING);
  cell.setCellValue("a test");
  
  // Write the output to a file
  FileOutputStream fileOut = new FileOutputStream("workbook.xls");
  wb.write(fileOut);
  fileOut.close();
  </code></pre>
  
  <p>and I get this error message:</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: org/dom4j/DocumentException
  </code></pre>
  
  <p>I add the xbean.jar to my library and to my run-time libraries.</p>
  
  <p>how can I resolve this exception?</p>
  
  <p>Thanks !</p>