CODEWITHSUNDEEP
javaservletszipdownload
Vinay
Vinay

Reputation: 183

Downloading a zip file returns a corrupt zip using servlets

I am trying to create a zip file using servlets but it returns me a corrupt zip file , here is the code for that in zipcontents function i am creating the zip , can someone help me out. Thanks in Advance.

public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
    IOException {

    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    res.setContentType("application/zip");
    res.setHeader("Content-Disposition", "attachment; filename=output.zip;");

    fsep = File.separator;
    rootDir = new File(getServletContext().getRealPath("Projects" + File.separator + "amrurta"));
    File list[] = rootDir.listFiles();
    zos = new ZipOutputStream(bout);
    zipContents(list, rootDir.getName() + fsep);
    zos.close();
    res.getWriter().println(bout.toString());
}

public void zipContents(File[] file, String dir) {
    // dir - directory in the zip file
    byte[] buffer = new byte[4096];
    try {

        for (int i = 0; i < file.length; i++) { // zip files
            if (file[i].isFile()) {
                fis = new FileInputStream(file[i]);
                zos.putNextEntry(new ZipEntry(dir + file[i].getName()));
                // shows how its stored
                // System.out.println(dir+file[i].getName());
                int bytes_read;
                while ((bytes_read = fis.read(buffer)) != -1)
                    zos.write(buffer, 0, bytes_read);

                fis.close();
            }
        } // for

        // create empty dir if theres no files inside
        if (file.length == 1)
            zos.putNextEntry(new ZipEntry(dir + fsep)); // this part is erroneous i think

        for (int i = 0; i < file.length; i++) { // zip directories
            if (file[i].isDirectory()) {
                File subList[] = file[i].listFiles();

                // for dir of varying depth
                File unparsedDir = file[i];
                String parsedDir = fsep + file[i].getName() + fsep; // last folder
                while (!unparsedDir.getParentFile().getName().equals(rootDir.getName())) {
                    unparsedDir = file[i].getParentFile();
                    parsedDir = fsep + unparsedDir.getName() + parsedDir;
                }
                parsedDir = rootDir.getName() + parsedDir; // add input_output as root

                zipContents(subList, parsedDir);
            }
        } // for

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

Upvotes: 0

Views: 4957

Answers (3)

MB.One
MB.One

Reputation: 108

You could create like this ZipOutputStream zipOut = new ZipOutputStream(res. getOutputStream()); And every zip entry you write into zip entry will be streamed back to the caller.

Upvotes: 0

Andriy Sholokh
Andriy Sholokh

Reputation: 872

One more possible reason is different JVM versions of application server and compiler which compiles servlet. Very rare issue but veeery hard to understand.

Upvotes: 0

BalusC
BalusC

Reputation: 1108712

There are too much problems in the code. the major ones which springs in are:

  1. The zos is been declared as servlet instance variable. This is not threadsafe. It is been shared among multiple requests. You risk that a subseuent request overwrites the previous one when it's not been finished.

  2. The binary ZIP content is been converted to character data with bout.toString(). This will definitely corrupt binary data. You should write binary data as binary data using the usual InputStream#read()/OutputStream#write() loop.

  3. The code does not call zos.closeEntry() at end of each entry.

I think #2 is the major cause. You don't need ByteArrayOutputStream. It's only an unnecessary memory hog. Just wrap the response.getOutputStream() in ZipOutputStream.

ZipOutputStream output = new ZipOutputStream(response.getOutputStream());
zipFiles(directory.listFiles(), output);
output.close();

Upvotes: 3

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