Navigation

Unlocking Excel Spreadsheets With JExcelApi

Introduction

Microsoft Excel allows users to password protect spreadsheets in a workbook. Protected spreadsheets can only be modified by entering the password (selected by the person who protected the spreadsheet).

Sometimes these passwords are lost, and we are left without the ability to modify said spreadsheets. There are utilities that can be used to either unlock or recover the password, but sometimes these tools are not available. Luckily, with a little bit of programming expertise and the help of a Java library called JExcelApi, we can fairly easily unlock an Excel spreadsheet.

JExcelApi

JExcelApi is an open source Java library to read, write and manipulate Microsoft Excel spreadsheets. JExcelApi is distributed under the GNU Lesser General Public License (LGPL). With the help of JExcelApi, we can load a password protected Microsoft Excel spreadsheet into memory, unprotect any protected sheets, and write back an unprotected copy back to disk. The following code example illustrates how to do this.

The Code

The following code fragment illustrates how to read a Microsoft Excel spreadsheet into memory, unprotect any protected sheets, and write back an unprotected version of the Excel spreadsheet back to disk.


package net.ensode.jexcelapitest;

import java.io.File;
import java.io.IOException;

import jxl.Workbook;
import jxl.read.biff.BiffException;
import jxl.write.WritableSheet;
import jxl.write.WritableWorkbook;
import jxl.write.WriteException;

public class JExcelApiTest
{
  public static void main(String[] args)
  {
    try
    {
      Workbook workbook = Workbook.
          getWorkbook(new File("/path/to/protected.xls"));
      WritableWorkbook copy = Workbook.
          createWorkbook(new File("/path/to/unprotected.xls"), workbook);

      WritableSheet[] sheets =  copy.getSheets();

      for (WritableSheet sheet : sheets)
      {
        sheet.getSettings().setProtected(false);
      }

      copy.write();
      copy.close();
    }
    catch (BiffException e)
    {
      e.printStackTrace();
    }
    catch (IOException e)
    {
      e.printStackTrace();
    }
    catch (WriteException e)
    {
      e.printStackTrace();
    }

  }

}

As can be seen in the above example, we can read an existing Excel spreadsheet into memory by calling the Workbook.getWorkbook(). method. This method takes an instance of java.io.File as its only parameter, and returns an instance of the jxl.Workbook class, this object contains an in-memory representation of the spreadsheet.

Once we have an in-memory representation of the Excel spreadsheet, we can create an in-memory copy of it by calling the Workbook.createWorkbook() method, passing an instance of java.io.File containing the location where we want to write the unlocked spreadsheet, and the instance of jxl.Workbook we obtained earlier as parameters. This method call will return an instance of jxl.write.WritableWorkbook, wich is basically a modifiable in-memory representation of the Excel spreadsheet.

To unlock or unprotect any password protected sheets in the workbook, we call the WriteableWorkbook.getSheets() method. This method will return an array of jxl.write.WritableSheet objects. These objects represent sheets in the workbook. To unprotect any protected sheets, we traverse the array (note: the example code above uses the enhanced for loop introduced in JDK 1.5, it will not compile under earlier versions of the JDK) and call the getSettings.getProtected(false) on each element of the array. This will effectively unprotect any protected sheets in the workbook. Finally, we write the unprotected workbook to disk by calling the WriteableWorkbook.write() method, and close the workbook by invoking its close() method.