download zip file using java?

Question

I am downloading zip file from web server using Java but somehow I am loosing about 2kb in each file. I don't know why since same code works fine with other formats, e.g, text, mp3 and extra. any help is appreciated? here is my code.

public void download_zip_file(String save_to) {
    try {
        URLConnection conn = this.url.openConnection();
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.setRequestProperty("content-type", "binary/data");
        InputStream in = conn.getInputStream();
        FileOutputStream out = new FileOutputStream(save_to + "tmp.zip");

        byte[] b = new byte[1024];
        int count;

        while ((count = in.read(b)) > 0) {
            out.write(b, 0, count);
        }
        out.close();
        in.close();

    } catch (IOException e) {
        e.printStackTrace();
    }
}

Answer 1

Try to remove the lines:

conn.setDoOutput(true);
conn.setDoInput(true);
conn.setRequestProperty("content-type", "binary/data");

Answer 2

It should be:

while ((count = in.read(b)) >= 0)

in.read can return 0.

Answer 3

I had a problem with downloading zip files from http once that turned out to be that my downloads included http headers in their beginning, but that made my files a bit larger not smaller, so you probably don't have this problem.

As a side note you might consider using Apache Commons Net for download related apps - it's really great.

Answer 4

A few years ago I remember running into a problem with an old version of Tomcat (5.5.25 for memory) that would cause largish downloads to be truncated. We fixed this by upgrading to a 5.5.27. I also recall the same problem was found and fixed in an early Tomcat 6.0 release.

If this rings any bells for you, take a look at the Tomcat change logs.

Answer 5

Only zip files, huh? Very odd. Is it from any server, or just this one? If you rename the file (change extension) do you get the same problem? Which bytes are missing? Are you sure it's the last 2K bytes and not some chunk from the middle/etc... ?

Answer 6

Put an out.flush() just after the " while ((count = in.read(b)) > 0) {...}" and before the out.close().