Reading from a ZipInputStream into a ByteArrayOutputStream?

ZipStream. Read(tempBuffer) if it's returning -1, then the zipStream is closed before you get it, and all bets are off.It's time to use your debugger and make sure what's being passed to you is actually valid When you call getNextEntry(), does it return a value, and is the data in the entry meaningful (i.e. Does getCompressedSize() return a valid value)?

IF you are just reading a Zip file that doesn't have read-ahead zip entries embedded, then ZipInputStream isn't going to work for you Some useful tidbits about the Zip format: Each file embedded in a zip file has a header. This header can contain useful information (such as the compressed length of the stream, it's offset in the file, CRC) - or it can contain some magic values that basically say 'The information isn't in the stream header, you have to check the Zip post-amble Each zip file then has a table that is attached to the end of the file that contains all of the zip entries, along with the real data. The table at the end is mandatory, and the values in it must be correct.

In contrast, the values embedded in the stream do not have to be provided If you use ZipFile, it reads the table at the end of the zip. If you use ZipInputStream, I suspect that getNextEntry() attempts to use the entries embedded in the stream. If those values aren't specified, then ZipInputStream has no idea how long the stream might be.

The inflate algorithm is self terminating (you actually don't need to know the uncompressed length of the output stream in order to fully recover the output), but it's possible that the Java version of this reader doesn't handle this situation very well I will say that it's fairly unusual to have a servlet returning a ZipInputStream (it's much more common to receive an inflatorInputStream if you are going to be receiving compressed content.

ZipStream. Read(tempBuffer) if it's returning -1, then the zipStream is closed before you get it, and all bets are off.It's time to use your debugger and make sure what's being passed to you is actually valid. When you call getNextEntry(), does it return a value, and is the data in the entry meaningful (i.e.

Does getCompressedSize() return a valid value)? IF you are just reading a Zip file that doesn't have read-ahead zip entries embedded, then ZipInputStream isn't going to work for you. Some useful tidbits about the Zip format: Each file embedded in a zip file has a header.

This header can contain useful information (such as the compressed length of the stream, it's offset in the file, CRC) - or it can contain some magic values that basically say 'The information isn't in the stream header, you have to check the Zip post-amble'. Each zip file then has a table that is attached to the end of the file that contains all of the zip entries, along with the real data. The table at the end is mandatory, and the values in it must be correct.

In contrast, the values embedded in the stream do not have to be provided. If you use ZipFile, it reads the table at the end of the zip. If you use ZipInputStream, I suspect that getNextEntry() attempts to use the entries embedded in the stream.

If those values aren't specified, then ZipInputStream has no idea how long the stream might be. The inflate algorithm is self terminating (you actually don't need to know the uncompressed length of the output stream in order to fully recover the output), but it's possible that the Java version of this reader doesn't handle this situation very well. I will say that it's fairly unusual to have a servlet returning a ZipInputStream (it's much more common to receive an inflatorInputStream if you are going to be receiving compressed content.

ZipInputStream in java DOES NOT HANDLE THIS WELL. Thank you for posting this. – Ethan Heilman Jul 17 '09 at 19:14.

I suppose you tried reading from a FileInputStream like this: ZipInputStream in = new ZipInputStream(new FileInputStream(...)); This WON'T work! Anyway, use ZipFile and also don't reinvent the wheel. Use commons-io where possible!

This usually looks like this: ZipFile zipFile = new ZipFile("foo. Zip"); InputStream in = null; ByteArrayOutputStream out = null; try { in = zipFile. GetInputStream(zipFile.

GetEntry("fileInTheZip")); out = new ByteArrayOutputStream(); IOUtils. Copy(in, out); } finally { IOUtils. CloseQuietly(in); IOUtils.

CloseQuietly(out); } You might also be interested in FileUtils if you don't know that class yet!

You could implement your own wrapper around the ZipInputStream that ignores close() and hand that off to the third-party library. ThirdPartyLib. HandleZipData(new CloseIgnoringInputStream(zipStream)); class CloseIgnoringInputStream extends InputStream { private ZipInputStream stream; public CloseIgnoringInputStream(ZipInputStream inStream) { stream = inStream; } public int read() throws IOException { return stream.read(); } public void close() { //ignore } public void reallyClose() throws IOException { stream.close(); } }.

This is an interesting idea....if nothing else works, I will probably try this. – pkaeding Sep 16 '08 at 3:52.

I'd use IOUtils from the commons io project. IOUtils. Copy(zipStream, byteArrayOutputStream).

This looks like it might work. I will try it when I get to work tomorrow. Thanks.

– pkaeding Sep 15 '08 at 23:49.

I would call getNextEntry() on the ZipInputStream until it is at the entry you want (use ZipEntry.getName() etc. ). Calling getNextEntry() will advance the "cursor" to the beginning of the entry that it returns. Then, use ZipEntry.getSize() to determine how many bytes you should read using zipInputStream.read().

I actually have called getNextEntry() before getting to this snippet. I just added some clarifiaction to the question. – pkaeding Sep 16 '08 at 2:07.

It is unclear how you got the zipStream. It should work when you get it like this: zipStream = zipFile. GetInputStream(zipEntry).

I just added a clarification about this, but it isn't comiing from a file. – pkaeding Sep 15 '08 at 23:48.

T is unclear how you got the zipStream. It should work when you get it like this: zipStream = zipFile. GetInputStream(zipEntry) If you are obtaining the ZipInputStream from a ZipFile you can get one stream for the 3d party library, let it use it, and you obtain another input stream using the code before.

Remember, an inputstream is a cursor. If you have the entire data (like a ZipFile) you can ask for N cursors over it. A diferent case is if you only have an "GZip" inputstream, only an zipped byte stream.In that case you ByteArrayOutputStream buffer makes all sense.

Please try code bellow private static byte getZipArchiveContent(File zipName) throws WorkflowServiceBusinessException { BufferedInputStream buffer = null; FileInputStream fileStream = null; ByteArrayOutputStream byteOut = null; byte data = new byteBUFFER; try { try { fileStream = new FileInputStream(zipName); buffer = new BufferedInputStream(fileStream); byteOut = new ByteArrayOutputStream(); int count; while((count = buffer. Read(data, 0, BUFFER))! = -1) { byteOut.

Write(data, 0, count); } } catch(Exception e) { throw new WorkflowServiceBusinessException(e.getMessage(), e); } finally { if(null! = fileStream) { fileStream.close(); } if(null! = buffer) { buffer.close(); } if(null!

= byteOut) { byteOut.close(); } } } catch(Exception e) { throw new WorkflowServiceBusinessException(e.getMessage(), e); } return byteOut.toByteArray(); }.

Check if the input stream is positioned in the begging. Otherwise, as implementation: I do not think that you need to write to the result stream while you are reading, unless you process this exact stream in another thread. Just create a byte array, read the input stream, then create the output stream.

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