Access Is Denied using NIO
Hello,
I am attempting to build a file transfer method that transfers a buffer of bytes at a time because I am using modems as my lower layer transfer method. (I dont have a choice on that one.) What happens is when I get disconnected I have to start over with the transfer and I dont want to do that. I want to keep up with the last byte successfully transferred so I can redial the connection, and pick up where I left off. I questioned about this yesterday but really didnt get a whole lot of help.
Here is a method that I have writte to do this job using NIO. I chose NIO because it seems faster and I have to compare files across a modem connection to make sure they have the correct versions of the exectuables.
Never the less this method throws an java.io.IOException: Access is denied exception when it gets the last byte. What I have found is that the last byte is either negative or the last byte has a remainder left over.
So given the file Source file c:\DJ\REMOTE_BIN\dcompres.exe has length of 29656 total bytes. From what I can tell, if this file isnt divisible by 512 then the last byte throws an exection. What doesnt make sense to me is why it throws Access Denied...
I did a small test and discovered that if I change the buffer to a 2, which would make even value length files divisible by 2 transfer just fine without the exception.
I have read through the transferFrom method and did not find where it throws this Access Denied exception.
What am I doing wrong here?
// Upload the package to the system.
publicstaticboolean uploadPackage(String sourceFile,String targetFile){
long bytePosition = 0;
int buffer = 512;
System.out.println("Copying executable " + sourceFile +" " + targetFile);
try{
// Create channel on the source
FileChannel srcChannel =new FileInputStream(sourceFile).getChannel();
// Create channel on the destination
FileChannel dstChannel =new FileOutputStream(targetFile).getChannel();
System.out.println("Source file " + sourceFile +" has length of " + srcChannel.size());
while (srcChannel.position() < srcChannel.size()){
dstChannel.transferFrom(srcChannel, srcChannel.position(), buffer);
// bytePosition = srcChannel.position();
System.out.println("Byte Position " + srcChannel.position());
}
// Close the channels
srcChannel.close();
dstChannel.close();
System.out.println("FILE COPY OKAY");
returntrue;
}catch (IOException e){
vlicMessageDetail ="IO EXCEPTION OCCURRED " + e;
pushRunTimeLog("[UPLOAD PACKAGE] (FATAL) :: IOEXCEPTION " + e);
System.out.println("IO EXCEPTION " + e);
returnfalse;
}
}
Message was edited by:
gsxrJava
[3881 byte] By [
gsxrJavaa] at [2007-10-3 3:22:27]
The reason why is because I playing with the buffer lengths to see if the buffer had anything to do with the issue and I discovered that it had nothing to do with the issue.
The files that I am sending are large and I am looking to decrease talk time on a long distance phone call. If I can transfer all of the file at one time then that is great, but sometimes I get disconnected, so I need to pick up where I left off and append the next bytes to the bytes already written to the harddrive. Does that make sense?
In my code, If I get disconnected during the uploadPackage method, I will redial() the connection, then continue transferring data to the remote site. What I keep up with in the previous method is the position of the file so that I can start at that position and append the bytes to that file until I have a complete file.
The final problem is that the las amount left is less than 512.
I am thinking that I will go back with trust I/O Streams. I thought about using NIO because I use this method for file comparisons.
I just thought it would be better to use the same Library to do what I needed.
here is the code I use for the file comparison across a modem connection. Not that it really matters but perhaps somebody might be looking for an efficient way to compare files across a low bandwidth connection.
// Check remote machine for the correct executable
public static boolean compareFiles(String sourceFile, String targetFile) {
System.out.println("FILE COMPARE (INFO) :: COMPARING " + sourceFile + " AND " + targetFile");
try {
RandomAccessFile sourceFileRa = new RandomAccessFile(sourceFile,"r");
RandomAccessFile targetFileRa = new RandomAccessFile(targetFile,"r");
FileChannel sourceChannel = sourceFileRa.getChannel();
MappedByteBuffer sourceBuffer = sourceChannel.map(FileChannel.MapMode.READ_ONLY, 0, sourceFileRa.length());
FileChannel targetChannel = targetFileRa.getChannel();
MappedByteBuffer targetBuffer = targetChannel.map(FileChannel.MapMode.READ_ONLY, 0, targetFileRa.length());
while (sourceBuffer.position() < sourceFileRa.length()) {
byte sourceByteArray[] = null;
byte targetByteArray[] = null;
sourceByteArray = new byte[(int)sourceFileRa.length()];
targetByteArray = new byte[(int)targetFileRa.length()];
sourceBuffer.get(sourceByteArray);
targetBuffer.get(targetByteArray);
System.out.println("Source Byte array " + sourceBuffer);
if(sourceByteArray.length != targetByteArray.length) {
return false;
}
else {
for(int x=0; x< sourceByteArray.length; x++) {
//System.out.println("Source Byte Array Bytes " + sourceByteArray[x]);
if(sourceByteArray[x] != targetByteArray[x]) {
sourceChannel.close();
targetChannel.close();
sourceFileRa.close();
targetFileRa.close();
return false;
}
}
}
}
sourceChannel.close();
targetChannel.close();
sourceFileRa.close();
targetFileRa.close();
return true;
} catch (Exception e) {
return false;
}
}
Message was edited by:
gsxrJava
Message was edited by:
gsxrJava
Message was edited by:
gsxrJava
