Okay, I now believe that this is the problem:
ZipInputStream zis = new ZipInputStream(in);
out = new FileOutputStream(entryDestination);
out.write(zis.read());
out.flush();
out.close();
You're creating a new file, and writing a single byte to it. That's not going to be a valid Excel file of any description. You're also failing to close streams using finally
blocks, but that's a different matter. To copy the contents of one stream to another, you want something like:
byte[] buffer = new byte[8192];
int bytes;
while ((bytes = input.read(buffer)) > 0) {
output.write(buffer, 0, bytes);
}
That said, you'd be better off using a 3rd party library to hide all of this detail - look at Guava and its ByteStreams
and Files
classes for example.
It's worth taking a step back and working out why you didn't spot this problem for yourself, by the way. For example, the first thing I'd have done would be to look at the directory where the files were unzipped, and try to open those files. Just seeing a bunch of 1-byte files would be a bit of a giveaway. When trying to diagnose an issue, it's vital that you can split a big problem into small ones, and work out which small one is at fault.