some example to send big file from server to client?

[Trustin Lee]

Actually you can achieve more reliable and faster transfer using
ChannelFutureListener.  The following is the code snippet I used when
I write an HTTP-based file server:

    ChannelFuture writeFuture = e.getChannel().write(httpResponseHeader);
    final long fileLength = file.length();
    final FileInputStream fis = new FileInputStream(file);
    writeFuture.addListener(new ChannelFutureListener() {
        private final ChannelBuffer buffer = ChannelBuffers.buffer(4096);
        private long offset = 0;

        public void operationComplete(ChannelFuture future)
                throws Exception {
            if (!future.isSuccess()) {
                future.getCause().printStackTrace();
                future.getChannel().close();
                fis.close();
                return;
            }

            System.out.println("SENDING: " + offset + " / " + fileLength);
            buffer.clear();
            buffer.writeBytes(fis, (int) Math.min(fileLength - offset,
                    buffer.writableBytes()));
            offset += buffer.writerIndex();
            ChannelFuture chunkWriteFuture =
                    future.getChannel().write(buffer);
            if (offset < fileLength) {
                // Send the next chunk
                chunkWriteFuture.addListener(this);
            } else {
                // Wrote the last chunk - close the connection if the
write is done.
                System.out.println("DONE: " + fileLength);
                chunkWriteFuture.addListener(ChannelFutureListener.CLOSE);
                fis.close();
            }
        }
    });

— Trustin Lee, http://gleamynode.net/



On Fri, May 22, 2009 at 3:48 AM, Frederic Bregier <fredbregier at free.fr> wrote:
>
> Hi,
>
> I think that you can even improve it by taking care of write ability like
> "discard" example shows. Indeed, in your code, if the network link is slow,
> you can have the side effect in the client to fill the write queue so much
> that there will be an OOME.
>
> A simple implementation idea could be as follow (from your code example):
>
>                FileInputStream fis = new FileInputStream(f);
>                int len;
>                byte[] bs = new byte[1024];
>                while ((len = fis.read(bs)) > 0) {
>                    ChannelBuffer buffer = ChannelBuffers.copiedBuffer(bs);
>                    // directly create and copy the ChannelBuffer from the
> byte array
>                    while (! channel.isWritable()) {
>                         Thread.sleep(10); // wait a while (maybe more than
> 10ms)
>                         // until channel is writable again
>                    }
>                    channel.write(buffer);
>                }
>                fis.close();
>
> Of course, if you have a client Handler, then you can directly code this in
> the handler such that you can even prevent your code of this active wait
> loop (see Discard example to see how).
>
> HTH too,
> Frederic
>
>
> tantom wrote:
>>
>> hi
>>
>> thanks,it's ok. below it's my test code,i post it hope to help next who
>> encount same with me:)
>>
>>  File f = new File("g:\\test.msi");
>>                 String params = "GetFile|test.msi";
>>                 byte[] bsParams = params.getBytes("UTF-8");
>>                 ChannelBuffer response = ChannelBuffers.buffer(8 +
>> bsParams.length);
>>
>> response.writeBytes(CTypeConvert.int2byte(bsParams.length));
>>                 response.writeBytes(CTypeConvert.int2byte((int)
>> f.length()));
>>                 response.writeBytes(bsParams);
>>
>>                 //write the header info first
>>                 channel.write(response);
>>
>>
>>                 FileInputStream fis = new FileInputStream(f);
>>                 int len;
>>                 byte[] bs = new byte[1024];
>>                 while ((len = fis.read(bs)) > 0) {
>>                     ChannelBuffer buffer = ChannelBuffers.buffer(len);
>>                     buffer.writeBytes(bs);
>>                     channel.write(buffer);
>>                 }
>>                 fis.close();
>>
>
>
> -----
> Hardware/Software Architect
> --
> View this message in context: http://n2.nabble.com/some-example-to-send-big-file-from-server-to-client--tp2952981p2953620.html
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>
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