CODEWITHSUNDEEP
javaftpdownloadcorrupt-dataapache-commons-net
Donald Whyte
Donald Whyte

Reputation: 295

Commons-Net FTPClient is not downloading files correctly

Solved

It turned out I misunderstood what the available() method actually does, so I just altered the code that wrote the data to this:

int b = input.read();
while (b != -1) {
    output.write(b);
    b = input.read();
}

I'll work on a more efficient reading/writing method another time, for now I'm just glad I've it working. Thanks for the help!

Original Post

I'm using the Commons-Net library to interact with a server via FTP and I've come across a problem when I try downloading files from the server to the local machine. I don't know if this is a bug in Comments-Net.FTPClient, but it's infinitely more likely I'm just not using the library correctly. That said, I haven't been able to find a solution when I googled the problem and example code I have seen appears to use the same method for downloading files as I do.

Anyway, the actual problem is that some of the files downloaded are completely empty, when they should contain data. It happens at random, so every time I download all the files, different files end up being empty each time. I'm assuming there is a problem with the way I'm reading the data from the server or writing it to a file.

Here's the code:

// For each file
InputStream input = ftp.retrieveFileStream(sourcePath);
ftp.completePendingCommand();

OutputStream output = new FileOutputStream(new File(destinationPath));
while (input.available() > 0) {
    output.write(input.read());
}

input.close();
output.close();

I'm pretty new to networking, so am I just being silly and doing something really simple wrong?

Upvotes: 1

Views: 1737

Answers (2)

powerMicha
powerMicha

Reputation: 2773

Check out commons-io with IOUtils and FileUtils for simpler stream processing

Upvotes: 0

Paul Cager
Paul Cager

Reputation: 1930

You shouldn't be using input.available() as that just tells you how much input is available without blocking. Loop until end of file instead (i.e. until read() returns -1).

http://download.oracle.com/javase/6/docs/api/java/io/InputStream.html#read()

If efficiency is a concern you could also try reading more than one byte at a time.

Upvotes: 2

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