Help with OutputStream.send() method. I want to know how much data this method already sent.

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Dalton Barreto - 05 Nov 2006 14:29 GMT

Hi,

I have a problem with my application that is:

Some times I have to send data to a server, and I do this using this
code:
First I have to get the sockWriter:

try {
            sock = getSocket();
            sockReader = sock.getInputStream();
            sockWriter = sock.getOutputStream();
            String recv = receiveSigleLineResponse();
    }catch (IOException e){
            throw new ConnectionException(e.getMessage());
}

ok, at this point everything works. The problem begins every time I
need to send the data, and here is the code:

sockWriter.write(new String(mailData + LINE_FEED + "." +
LINE_FEED).getBytes());

this lines works well, but once my program reaches this line of code,
it "hangs" until this function
returns, this is expected, of course. But I want the user to see a
progress bar showing how much data has already been sent to the server.
And I can't do this, because send() is blocking until all data have
been sent.
What I want is a way to keep checking how much data the function sent
so I can update the progress bar.

I don't know if I was clear, but thanks in advance.

Thanks!
Dalton Barreto;

Reply to this Message

Daniel Pitts - 05 Nov 2006 22:50 GMT

> Hi,
>
[quoted text clipped - 32 lines]
> Thanks!
> Dalton Barreto;

Two things.
One, don't send all of the bytes in one chunk. Split it into different
chunks.
Two, print out how many chunks have been sent so far.
Possibly having an 1024 byte chunk, you would be able to display(chunks
+ "k bytes have been sent")

Reply to this Message

Dalton Barreto - 06 Nov 2006 16:41 GMT

> > Hi,
> >
[quoted text clipped - 39 lines]
> Possibly having an 1024 byte chunk, you would be able to display(chunks
> + "k bytes have been sent")

So the class that sends the data has to know about the class that
implements the
progress bar, right?? This way the sender class will update the
progress directly, and
not the other way (the progress bar checking for total transfered
data), what is the
best way do implement this??

I tried to do something like this:
the class that sends the data increments a private variable, and the
class tha implements
the pBar keeps checking how much was sent so far. but this is bad,
because the only
way that I see to do this is: sleep some seconds e check again, then
get the totalBytes
transfered and do a += on the progerss status. But this is wrong,
because if the connection
is bad and the OS doesn't send any data in a short time slice the
progress bar would show
a inconsistent status (more data than actually transfered).

Is there any other way to do this 'comunication', between the sender
class and the pBar class, so the second show always a consistent status
value?

Thanks in advance!
Dalton Barreto;

PS: The class the send the data and the class that shows the progress
bar are two different
classes.

Reply to this Message

Daniel Pitts - 06 Nov 2006 20:47 GMT

> So the class that sends the data has to know about the class that
> implements the
[quoted text clipped - 27 lines]
> bar are two different
> classes.

Look up JProgressBar
(http://java.sun.com/j2se/1.5.0/docs/api/javax/swing/JProgressBar.html)
if you are doing this in Swing.
If not using Swing, you probably still want to use the observer
pattern.

Psuedo-code:

class Uploader {
ProgressListener listener; // You can also make this a list/array of
listeners
int progress = 0;
public void doUpload() {
for (Chunk chunk: chunksToUpload) {
uploadChunk(chunk);
listener.progressChanged(progress);
}
}
}

Alternativly , you could make progress a JavaBean bound property, and
have the progress listener be a PropertyChangeListener, but thats more
work for now, and until you need it, I suggest holding off.

If you are doing this in Swing, make sure your event is fired off in
the EventDispatchThread
(http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html)

Hope this helps. Good luck.

Reply to this Message

Dalton Barreto - 07 Nov 2006 12:08 GMT

> > So the class that sends the data has to know about the class that
> > implements the
[quoted text clipped - 57 lines]
>
> Hope this helps. Good luck.

It HELPS!! a Lot!! thanks!
I was thinking about a design pattern, and I'm sure that this will
solve my problem, and I will be
able to reuse this "upload class" anytime I need.

Thanks a lot Daniel.

PS: Yes, I'm doing this in Swing. :-)
Dalton Barreto;

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Help with OutputStream.send() method. I want to know how much data this method already sent.

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