Empty Folder when try to unzip using java.util.zip / zip4j

Question

i have receive a compressed file in zip extension. i cannot open it directly using windows explorer. i can extract it using 7Zip, it throws some error but the file still decompressed as expected. i can extract it using winrar, no error, file decompressed as expected.

then i tried to decompressed using java.util.unzip / zip4j.

java.util.zip code :

    public static void unzip(String zipFilePath,
                         String destDirectory) throws IOException {
    File destDir = new File(destDirectory);
    if (!destDir.exists()) {
        destDir.mkdir();
    }
    ZipInputStream zipIn =
        new ZipInputStream(new FileInputStream(zipFilePath));
    ZipEntry entry = zipIn.getNextEntry();
    // iterates over entries in the zip file
    while (entry != null) {
        String filePath = destDirectory + File.separator + entry.getName();
        if (!entry.isDirectory()) {
            // if the entry is a file, extracts it
            extractFile(zipIn, filePath);
        } else {
            // if the entry is a directory, make the directory
            File dir = new File(filePath);
            dir.mkdir();
        }
        zipIn.closeEntry();
        entry = zipIn.getNextEntry();
    }
    zipIn.close();
}

/**
 * Extracts a zip entry (file entry)
 * @param zipIn
 * @param filePath
 * @throws IOException
 */
private static void extractFile(ZipInputStream zipIn,
                                String filePath) throws IOException {
    BufferedOutputStream bos =
        new BufferedOutputStream(new FileOutputStream(filePath));
    byte[] bytesIn = new byte[BUFFER_SIZE];
    int read = 0;
    while ((read = zipIn.read(bytesIn)) != -1) {
        bos.write(bytesIn, 0, read);
    }
    bos.close();
}

with above code, no error happen, but i get a empty folder.

zip4j code :

        String zipFilePath = "C:\\Juw\\JR\\file\\output\\020030214112016.zip";
    //String zipFilePath = "C:\\Juw\\JR\\file\\output\\myFile.zip";
    String destDirectory = "C:\\Juw\\JR\\file\\output\\targetUnzip";

    try {
        ZipFile zipFile = new ZipFile(zipFilePath);
        zipFile.extractAll(destDirectory);

    } catch (Exception ex) {
        ex.printStackTrace();
    }

and there's exception : net.lingala.zip4j.exception.ZipException: zip headers not found. probably not a zip file

if i tried to decompressed the file using winrar, and then i compressed it using windows built in zip feature. i can decompressed it succesfully using my code. and the size is different between mine and the client gave me. mine is 508kb, and the other one is 649kb.

question is : - are there any java library that utilize / as powerful winrar, that can extract the compressed file without error ? - what is the best practices to resolve this case ?

Many thanks in advance :)

"what is the best practices to resolve this case ?" - Ask the client to provide valid .zip files. — JimmyB, Nov 15 '16 at 12:16
hi JimmyB, are you suspecting the the zip files is not valid ? because winrar can extract it without any problem. is it possible that the client compressed it using 3rd party apps that have a different standard zip ? or from other OS (not windows) ? — cumibulat, Nov 16 '16 at 00:03
If Windows and 7zip and the Java lib fail or report an error, I think chances are that the file is in some way not fully valid. Maybe it's not even a zip file but some other format written to a file named .zip. Tools which do not rely on the file name to determine what fomat the file actually has may be able to decompress it still. — JimmyB, Nov 16 '16 at 13:10

score 0 · Answer 1 · answered Nov 18 '16 at 01:30

Thanks to all respondents that have been helping me out.

So the case is this gzip file (named as .zip extension) have a empty string at the end of file. So it threwing error like i mention in previous post. With below code that i get from my colleague, the problem is solved. I post it so maybe other user can use it in the future.

public void gunzipIt(){

 byte[] buffer = new byte[1024];
 boolean isValid = true;

 try{

     GZIPInputStream gzis =
        new GZIPInputStream(new FileInputStream(INPUT_GZIP_FILE));

     FileOutputStream out =
        new FileOutputStream(OUTPUT_FILE);

    while (isValid) {

        int len;

        try{
            len = gzis.read(buffer);
        }catch(Exception ex){
            len = 0;
            isValid = false;
        }

        if (len > 0) {
            out.write(buffer, 0, len);
        }else{

            isValid = false;
        }
    }

    gzis.close();
    out.close();

    System.out.println("Done");

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

}

Empty Folder when try to unzip using java.util.zip / zip4j

1 Answers1