CODEWITHSUNDEEP
javazip
Kico Lobo
Kico Lobo

Reputation: 4404

How to check if a generated zip file is corrupted?

we have a piece of code which generates a zip file on our system. Everything is ok, but sometimes this zip file while opened by FilZip or WinZip is considered to be corrupted.

So here is my question: how can we check programatically if a generated zip file is corrupted?

Here is the code we are using to generate our zip files:

try {
    ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(tmpFile));
    byte[] buffer = new byte[16384];
    int contador = -1;
    for (DigitalFile digitalFile : document.getDigitalFiles().getContent()) {
       ZipEntry entry = new ZipEntry(digitalFile.getName());
       FileInputStream fis = new FileInputStream(digitalFile.getFile());
       try {
          zos.putNextEntry(entry);
          while ((counter = fis.read(buffer)) != -1) {
             zos.write(buffer, 0, counter);
          }
          fis.close();
          zos.closeEntry();
       } catch (IOException ex) {
          throw new OurException("It was not possible to read this file " + arquivo.getId());
       }
    }
    try {
      zos.close();
    } catch (IOException ex) {
      throw new OurException("We couldn't close this stream", ex);
    }

Is there anything we are doing wrong here?

EDIT: Actually, the code above is absolutely ok. My problem was that I was redirecting the WRONG stream for my users. So, instead of opening a zip file they where opening something completely different. Mea culpa :(

BUT the main question remains: how programatically I can verify if a given zip file is not corrupted?

Upvotes: 28

Views: 39745

Answers (9)

Leonis
Leonis

Reputation: 296

I simplified the code from Nikhil Das Nomula by using try-with-resources:

    public static boolean isValidZipFile(File file) {
        try(ZipFile zipfile = new ZipFile(file); 
            ZipInputStream zis = new ZipInputStream(new FileInputStream(file))
        ) {
            ZipEntry ze = zis.getNextEntry();
            if (ze == null) {
                return false;
            }
            while (ze != null) {
                // if it throws an exception fetching any of the following then we know the file is corrupted.
                zipfile.getInputStream(ze);
                ze.getCrc();
                ze.getCompressedSize();
                ze.getName();

                ze = zis.getNextEntry();
            }
            return true;
        } catch (Exception e) {
            return false;
        }
    }

At first I thought using ZipFile was redundant, but then I deleted one byte at the end of the archive file. ZipEntry did not show the problem, but ZipFile threw the error java.util.zip.ZipException: zip END header not found.

Upvotes: 0

Arnaud
Arnaud

Reputation: 531

You can use the ZipFile class to check your file :

 static boolean isValid(final File file) {
    ZipFile zipfile = null;
    try {
        zipfile = new ZipFile(file);
        return true;
    } catch (IOException e) {
        return false;
    } finally {
        try {
            if (zipfile != null) {
                zipfile.close();
                zipfile = null;
            }
        } catch (IOException e) {
        }
    }
}

Upvotes: 35

Nikhil Das Nomula
Nikhil Das Nomula

Reputation: 1953

I know its been a while that this has been posted, I have used the code that all of you provided and came up with this. This is working great for the actual question. Checking if the zip file is corrupted or not

private boolean isValid(File file) {
    ZipFile zipfile = null;
    ZipInputStream zis = null;
    try {
        zipfile = new ZipFile(file);
        zis = new ZipInputStream(new FileInputStream(file));
        ZipEntry ze = zis.getNextEntry();
        if(ze == null) {
            return false;
        }
        while(ze != null) {
            // if it throws an exception fetching any of the following then we know the file is corrupted.
            zipfile.getInputStream(ze);
            ze.getCrc();
            ze.getCompressedSize();
            ze.getName();
            ze = zis.getNextEntry();
        } 
        return true;
    } catch (ZipException e) {
        return false;
    } catch (IOException e) {
        return false;
    } finally {
        try {
            if (zipfile != null) {
                zipfile.close();
                zipfile = null;
            }
        } catch (IOException e) {
            return false;
        } try {
            if (zis != null) {
                zis.close();
                zis = null;
            }
        } catch (IOException e) {
            return false;
        }

    }
}

Upvotes: 12

albfan
albfan

Reputation: 12940

new ZipFile(file)

compress again the file, so duplicate efforts and that is not what you are looking for. Despite of the fact that only check one file and the question compress n-files.

Take a look to this: http://www.kodejava.org/examples/336.html

Create a checksum for your zip:

CheckedOutputStream checksum = new CheckedOutputStream(fos, new CRC32());
ZipOutputStream zos = new ZipOutputStream(new BufferedOutputStream(checksum));
...

And when you finish the compression show it

System.out.println("Checksum   : " + checksum.getChecksum().getValue());

You must do the same reading the zip with java or others tools checking if checksums match.

see https://stackoverflow.com/a/10689488/848072 for more information

Upvotes: 1

Sören
Sören

Reputation: 21

in my implementation it looks like that. maybe it helps you:

//[...]

try {
    FileInputStream fis = new FileInputStream(file);
    BufferedInputStream bis = new BufferedInputStream(fis);

    zos.putNextEntry(new ZipEntry(file.getName()));

    try {
        final byte[] buf = new byte[BUFFER_SIZE];
        while (true) {
            final int len = bis.read(buf);
            if (len == -1) {
                break;
            }
            zos.write(buf, 0, len);
        }
        zos.flush();
        zos.closeEntry();
    } finally {
        try {
            bis.close();
        } catch (IOException e) {
            LOG.debug("Buffered Stream closing failed");
        } finally {
            fis.close();
        }
    }
} catch (IOException e) {
    throw new Exception(e);
}

//[...]
zos.close

Upvotes: 2

stacker
stacker

Reputation: 68942

Your code is basically OK, try to find out which file is responsible for the corrupted zip file. Check whether digitalFile.getFile() always returns a valid and accessible argument to FileInputStream. Just add a bit logging to your code and you will find out what's wrong.

Upvotes: 1

Waverick
Waverick

Reputation: 2065

Perhaps swap the following two lines?;

fis.close();
zos.closeEntry();

I can imagine that the closeEntry() will still read some data from the stream.

Upvotes: 1

user7094
user7094

Reputation:

ZipOutputStream does not close the underlying stream.

What you need to do is:

FileOutputStream fos = new FileOutputStream(...);
ZipOutputStream zos = new ZipOutputStream(fos);

Then in your closing block:

zos.close();
fos.flush(); // Can't remember whether this is necessary off the top of my head!
fos.close();

Upvotes: 0

John Doe
John Doe

Reputation: 166

I think you'll see correspondent exception stack trace during zip-file generation. So, you probably wan't to enhance your exception handling.

Upvotes: 3

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