Corrupted zip file using ZipOutputStream

user_10838532 0
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I'm trying to create a zip file to be able to send multiple files over http.

My issue is that the Zip file that is generated is "corrupted" before and after the file has been send. The issue is i'm not able to find what i did wrong as i'm getting no errors inside the console.

So does someone has an idea file my generated zip file is corrupted ?

This is my code :

  OutputStream responseBody = t.getResponseBody();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ZipOutputStream zos = new ZipOutputStream(baos);


            int counter = 1;
            for (PDDocument doc : documents)
            {
                ZipEntry zipEntry = new ZipEntry("document" + counter);
                zos.putNextEntry(zipEntry);
                ByteArrayOutputStream docOs = new ByteArrayOutputStream();
                doc.save(docOs);
                docOs.close();
                zos.write(docOs.toByteArray());
                zos.closeEntry();
                zos.finish();
                zos.flush();

                counter++;
            }
            zos.close();
            baos.close();


            responseBody.write(baos.toByteArray());
            responseBody.flush();

Thank you for your help !

zipoutputstream java
1 Answers

You need to remove zos.finish() from inside the loop as it terminates the ZIP entries, as it is handled by zos.close() at end of the stream.

With very large streams you will be better off sending ZIP directly to responseBody bypassing ByteArrayOutputStream memory buffer.

If you are still having problems check the content type of the output is set. It might be easier to debug by temporarily writing the byte[] to file to check the ZIP format you are sending with:

Files.write(Path.of("temp.zip"), baos.toByteArray());

This outline below shows sending a simple ZIP over http (from a servlet, adjust the first 2 lines to appropriate calls for "t"). This may help you check which step of your code causes the corruption if you work back to adding your own document objects inside the loop:

// MUST set response content type:
// resp.setContentType("application/zip");
OutputStream out = resp.getOutputStream(); // or t.getResponseBody();
try(ZipOutputStream zos = new ZipOutputStream(out))
{
    while (counter-- > 0)
    {
        ZipEntry zipEntry = new ZipEntry("document" + counter+".txt");
        zos.putNextEntry(zipEntry);
        zos.write(("This is ZipEntry: "+zipEntry.getName()+"\r\n").getBytes());
    }
}
user_47127340
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