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FileChannel Problem specifically with ByteBuffer and FileChannel.MapMode

Posted on 2006-07-10
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Last Modified: 2012-06-21
Guys

Has anyone seen this?

I am trying some file manipulation...  concantenating file (using my concatenate method)

then after saving them I want to get rid of the files.  Almost of all of them are deleted EXCEPT the file I modifyied using

concatenate (not deleted using my cleanupFiles method)

I was trying to use

//ByteBuffer buffer = tmpChannel.map(FileChannel.MapMode.READ_ONLY, channel.position(), tmpChannel.size());

but had to change it to use a regular fileinputstream again... some reason it has the modified files under some sort of lock..  try all kinds of ways to make sure they were closed,,, to no avail




private void concatenate(List fileList, boolean lastItemFirst)
      throws Exception
      {
            Object[] fileArray = fileList.toArray();
            
            
            String fileName;
            FileChannel channel = null;
            FileOutputStream fs = null;
            File concatenatedFile = null;
            FileInputStream temps = null;
            int max = fileArray.length - 1;
            
            
            if (lastItemFirst)
            {
                  
                  for (int items = max; items >=0; items--)
                  {
                        
                        fileName = (String)fileArray[items];
                        
                        //last segment of a Data
                        if (items == max)
                        {
                              
                              concatenatedFile = new File(fileName);
                        try
                        {
                              fs = new FileOutputStream(fileName, true);
                        }
                        finally
                    {
                          try
                          {
                                if (fs != null) fs.close();
                          
                          }
                          catch(IOException e)
                          {
                                e.printStackTrace();
                          }
                    }
                        
                        
                              
                              
                              channel = fs.getChannel();
                              
                        }
                        else
                        {
                              File f = new File(fileName);
                              try
                              {
                                    temps = new FileInputStream(fileName);
                              }
                              finally
                          {
                                try
                                {
                                      if (temps != null) temps.close();
                                
                                }
                                catch(IOException e)
                                {
                                      e.printStackTrace();
                                }
                          }
                              
                              byte[] buffer = new byte[(int)f.length()];
                              temps.read(buffer);
                              FileChannel tmpChannel =temps.getChannel();
      /*** PART I had to comment out  */                        
                              //ByteBuffer buffer = tmpChannel.map(FileChannel.MapMode.READ_ONLY, channel.position(), tmpChannel.size());
                             //ByteBuffer buffer = tmpChannel.map(FileChannel.MapMode.READ_ONLY, channel.position(), tmpChannel.size()).asReadOnlyBuffer();
                              
                              //channel.write(buffer);
                             fs.write(buffer);
                              tmpChannel.close();
                              temps.close();
                        }
                  }
            
            }            
            
            fs.flush();
            channel.force(true);
            fs.close();
            concatenatedFile.delete();
            
      }
      
      
      public final void cleanupFiles(Collection msgList)
      throws Exception
      {
            
            Iterator it = msgList.iterator();
            
            boolean answer=false;
            boolean file_exists=false;
            while (it.hasNext())
            {
                  Data data = (Data)it.next();
                  
                  
                  Iterator fileIterator = data.getId().iterator();
                  
                  
                  while (fileIterator.hasNext())
                  {
                        String fileName = (String)fileIterator.next();
                        
                        
                        File file = new File(fileName);
                        file_exists=file.exists();
                        if (file_exists)
                        {
                              answer=file.delete();
                        }
                  }
            }
      }


Thanks
ryno71
0
Comment
Question by:ryno71
6 Comments
 
LVL 86

Expert Comment

by:CEHJ
ID: 17076642
You'd probably find it a lot easier to use this:

http://java.sun.com/j2se/1.5.0/docs/api/java/io/SequenceInputStream.html
0
 
LVL 92

Expert Comment

by:objects
ID: 17077891
you're closing the stream before you do the concatenation :)
should be something like:

             Iterator i = fileList.iterator();
             FileChannel out = new FileOutputStream(((File)i.next()).getChannel();
             long pos = 0;
             while (i.hasNext())
                 source = args[i];
                 FileChannel in = new FileInputStream(((File)i.next()).getChannel();
                 long size = in.size();
                 MappedByteBuffer buf = in.map(FileChannel.MapMode.READ_ONLY, pos, size);
                 out.write(buf);
                 pos += size;
                 in.close();
              }
0
 

Author Comment

by:ryno71
ID: 17081011
Actually I am seeing this issue below where I cant delete the file I've modified via the FileChannel.map

Cannot delete file if memory mapped with FileChannel.map (windows)

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4715154

dont think its ever been fixed
0
 
LVL 92

Expert Comment

by:objects
ID: 17086787
it'll get closed eventually, once the gc'er is done with it.
0
 
LVL 1

Accepted Solution

by:
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ID: 17185203
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