Fwd: [File Locking on xlsx] Data is not written...

[rahul.soa]

Hello Devs,

Can you please help me in this?

Many thanks!

Best Regards,
Rahul

---------- Forwarded message ----------
From: rahul.soa <rahul....@googlemail.com>
Date: Fri, Oct 14, 2011 at 3:19 PM
Subject: [File Locking on xlsx] Data is not written...
To: POI Users List <u...@poi.apache.org>


Hello Experts,

I am trying to use File lock in my GUI (which is deployed as Web Start
Application) to prevent concurrency issues.

However it does not work, I have below sample mentod:


void writeIntoTheFile(XSSFWorkbook defectWorkBook, File fileToWrite) {

            logger.debug("In writeIntoTheFile");



//Without file locking code - works well
   /* try{
    FileOutputStream out = new FileOutputStream(fileToWrite.getPath());
    defectWorkBook.write(out);
    out.close();
     }catch(IOException e){logger.debug("Here is error message" +
e.getMessage());} */



            FileLock lock = null;
            FileChannel channel = null;
            FileOutputStream out = null;

             try {
                channel = new RandomAccessFile(fileToWrite,
"rw").getChannel();
                logger.debug("trying to get the lock...");
                try{
                lock = channel.tryLock();
                 } catch (OverlappingFileLockException e) {
                     System.out.println("File is already locked" +
e.getMessage());
    }
                if (lock != null) {
                    logger.debug("Got the lock to write into the file...");
                    *out = new FileOutputStream(fileToWrite.getPath());*
<<<<< file gets corrupted here
                    logger.debug("about to write in the file...");
                    defectWorkBook.write(out);
                    logger.debug("written..");
                } else {
                    logger.debug("Another instance is already running");
                    JOptionPane.showMessageDialog(null, "Another instance is
already writing, Try after a few seconds.", "Write Error...",
JOptionPane.INFORMATION_MESSAGE);
                }
                    logger.debug("about to close the file...");
                    out.close();
                    logger.debug("closed..");

            } catch (Exception e) {
                //logger.debug(e.printStackTrace());
                System.out.println("Here is message" + e.getMessage());
                e.printStackTrace();
            }


          try{
            if (lock != null && lock.isValid()) {
                logger.debug("about to release the lock...");
                    lock.release();
                logger.debug("lock released...");
                }
                channel.close();

            }catch(IOException e){logger.debug("Here is error message" +
e.getMessage());}



}

In the above code, there is no exception thrown and all the debug statements
are displayed on the screen. However, if I try to append some records (data
fetched from data source) in existing XLSX workbook then whole workbook gets
corrupted. I checked it while debugging the application.And I found it
happens here

*out = new FileOutputStream(fileToWrite.getPath());

*then I passed true for append

*out = new FileOutputStream(fileToWrite.getPath(), true);
*
now above method executes correctly and while debugging I can see the values
in the rows and cells of MS excel workbook sheet (defectWorkBook), but
somehow they are not written on this statement defectWorkBook.write(out); No
exception is thrown at all. not sure why its not written in the actual file.





Can you please help me if I am really missing something?

Many Thanks in advance,
rahul