Java – extract the image into a blobstore

In my application, I need to do the following:

I successfully uploaded, decompressed and saved the file @ blobstore, but the image seems to be broken When I download them from the blobstore (just blobstoreservice. Serve them), the image color is wrong, or partially displayed, or damaged in other ways Attempting to use imagesservice will also throw an exception I checked the size of the image before compression, and decompressed the file size when writing to the blobstore, and they look the same This is my code:

ZipInputStream zis = ...; 
ZipEntry entry;
while ((entry =zis.getNextEntry()) !=null)
{
    String fileName = entry.getName().toLowerCase();
    if(fileName.indexOf(".jpg") != -1 || fileName.indexOf(".jpeg") != -1)       
     {
        FileService fileService = FileServiceFactory.getFileService();
        String mime = ctx.getMimeType(fileName);//getting mime from servlet context
        AppEngineFile file = fileService.createNewBlobFile(mime,fileName);
        boolean lock = true;
        FileWriteChannel writeChannel = fileService.openWriteChannel(file,lock);
        byte[] buffer = new byte[BlobstoreService.MAX_BLOB_FETCH_SIZE];
        while(zis.read(buffer) >= 0)
        {
           ByteBuffer bb = ByteBuffer.wrap(buffer);
           writeChannel.write(bb);
        }
        writeChannel.closeFinally();
        BlobKey coverKey =  fileService.getBlobKey(file);
        ....
     }
}

Thank you very much for your time!

UPD: I found a feasible solution, but I still don't understand why the first solution failed

int read;
            ByteArrayOutputStream baos = new ByteArrayOutputStream();

            while((read = zis.read()) >= 0)
            {
                baos.write(read);
                if(baos.size() == BlobstoreService.MAX_BLOB_FETCH_SIZE)
                {
                    ByteBuffer bb = ByteBuffer.wrap(baos.toByteArray());
                    writeChannel.write(bb);
                    baos = new ByteArrayOutputStream();
                }
            }
            if(baos.size() > 0)
            {
                ByteBuffer bb = ByteBuffer.wrap(baos.toByteArray());
                writeChannel.write(bb);
            }

Solution

Because ZIS Read may not fill the entire buffer

Use the following instead

int len;
while((len = zis.read(buffer)) >= 0){
  ByteBuffer bb = ByteBuffer.wrap(buffer,len);
  writeChannel.write(bb);
}

I hope it helps