Closing ZipOutputStream

Question

I'm a bit confused. I know that an empty zip is not legal. But what about this sample snippet:

ZipOutputStream zos = null; 
try
{
    zos = new ZipOutputStream(new FileOutputStream("..."));
    //
    //..
    //
}
finally
{
    zos.close();
}

If no zip entries had been added for some reason (possibly exceptional situation) then the following exception will be thrown on close attempt:

Exception in thread "main" java.util.zip.ZipException: ZIP file must have at least one entry
    at java.util.zip.ZipOutputStream.finish(ZipOutputStream.java:304)
    at java.util.zip.DeflaterOutputStream.close(DeflaterOutputStream.java:146)
    at java.util.zip.ZipOutputStream.close(ZipOutputStream.java:321)

In this situation what would be the cleanest way to close the stream?

Thanks...

Answer 1

You should close the FileOutputStream, not the ZipOutputStream, because the former is what actually consumes system resources.

File zipFile = new File("/tmp/example.zip");
FileOutputStream fos = null;
try
{
   fos = new FileOutputStream(zipFile);
   ZipOutputStream zos = new ZipOutputStream(fos);

   // ...

   zos.close();
}
catch (IOException ex)
{
   // log/report exception, then delete the invalid file
   IOUtils.closeQuietly(fos);
   zipFile.delete();
}
finally
{
   IOUtils.closeQuietly(fos);
}

The IOUtils class is found in Jakarta Commons IO. Using it means that you don't have to deal with the possible-but-rarely-useful IOException that can be thrown by close().