Compressing binary data in Java

2020-08-02 • Java

I tried to compress a set of binary data (the result set returned from the database) into a file It can be downloaded through a web application The following code is used to compress the result set and write the zip file to httpservletresponse

String outFilename = "outfile.zip";
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition","attachment; filename= " + outFilename);
OutputStream os = response.getOutputStream();
ZipOutputStream out = new ZipOutputStream(os);
for (int i = 0; i < cardFileList.size(); i++) {

    CardFile cardFile = cardFileList.get(i);
    out.putNextEntry(new ZipEntry(cardFile.getBinaryFileName()));
    out.write(cardFile.getBinaryFile(),cardFile.getBinaryFile().length);
    out.closeEntry();
}
// Complete the ZIP file
out.flush();
out.close();
os.close();

The problem is that when using WinRAR to extract the downloaded zip file, I receive the following error:

Can anyone point out where I made a mistake? Any help will be greatly appreciated

[editor] I tried response setContentType(“application / zip”); But the results are the same

Solution

The following codes apply to me:

FileOutputStream os = new FileOutputStream("out.zip");
ZipOutputStream zos = new ZipOutputStream(os);
try
{
    for (int i = 1; i <= 5; i++)
    {
        ZipEntry curEntry = new ZipEntry("file" + i + ".txt");
        zos.putNextEntry(curEntry);
        zos.write(("Good morning " + i).getBytes("UTF-8"));
    }
}
finally
{
    zos.close();
}

The zip file generated with this code is opened in 7 - Zip without any problem

>Check that the response from the servlet is not actually a 404 or 500 error page Select a small response and open it using a hex editor or even a text editor Zip files start with "PK" magic numbers and should be visible even in a text editor. > Try saving to a file instead of a beginner's servlet output stream to see if you can make a difference. > Is there a filter to modify the output / destroy zip of the servlet?

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Java