Download a zip from a servlet Java

Question

I don't understand why this is so hard and everybody has it's own implementation...

So in my server, I generate a .zip file which I want the user to be able to download upon click.

So I set up the request, which the server successfully receives and now, i'm struggling with writing the byte array to the output.

Here's my code for the response:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("Downloading clusters.zip");

        /* Generate the directory on the server, then zip it. */
        clustersToFiles();
        zipClusters();
        /* Now the zip is saved on zipFullPath */

        System.out.println("Done generating the .zip");

        String parent_dir = System.getProperty("catalina.base");
        String filename = "clusters.zip";
        String zipFullPath = parent_dir + "/" + filename;

        response.setContentType("application/zip");
        response.setHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");
        OutputStream out = response.getOutputStream();

        FileInputStream fis = new FileInputStream(zipFullPath);
        int bytes;
        while ((bytes = fis.read()) != -1) {
            System.out.println(bytes);
            out.write(bytes);
        }
        fis.close();
        response.flushBuffer();

        System.out.println(".zip file downloaded at client successfully");
}

Answer 1

The fact that the downloaded file is a ZIP isn't relevant (except for the content type), you just want to download a binary file.

PrintWriter isn't good at that, this writer is used to write text output, and the write(int) method you are using :

Writes a single character .

Just use a low level plain OutputStream , its write(int) method :

Writes the specified byte to this output stream.

So just go :

OutputStream out = response.getOutputStream();

You may find some more ways of doing it in this question : Implementing a simple file download servlet