java - 在 Google App Engine 上用 java 解压缩一个大 blob

Question

我正在使用 Java (JDO) 在 Google App Engine 上构建一些东西。我正在使用 Deflater 以编程方式压缩一个大 byte[]，然后将压缩后的 byte[] 存储在 blobstore 中。这很好用:

 public class Functions {

public static byte[] compress(byte[] input) throws UnsupportedEncodingException, IOException, MessagingException
    {

        Deflater df = new Deflater();       //this function mainly generate the byte code
        df.setLevel(Deflater.BEST_COMPRESSION);
        df.setInput(input);

        ByteArrayOutputStream baos = new ByteArrayOutputStream(input.length);   //we write the generated byte code in this array
        df.finish();
        byte[] buff = new byte[1024];   //segment segment pop....segment set 1024
        while(!df.finished())
        {
            int count = df.deflate(buff);       //returns the generated code... index
            baos.write(buff, 0, count);     //write 4m 0 to count
        }
        baos.close();

        int baosLength = baos.toByteArray().length;
        int inputLength = input.length;
        //System.out.println("Original: "+inputLength);
        // System.out.println("Compressed: "+ baosLength);

        return baos.toByteArray();

    }

 public static byte[] decompress(byte[] input) throws UnsupportedEncodingException, IOException, DataFormatException
    {

        Inflater decompressor = new Inflater();
        decompressor.setInput(input);

        // Create an expandable byte array to hold the decompressed data
        ByteArrayOutputStream bos = new ByteArrayOutputStream(input.length);

        // Decompress the data
        byte[] buf = new byte[1024];
        while (!decompressor.finished()) {
            try {
                int count = decompressor.inflate(buf);
                bos.write(buf, 0, count);
            } catch (DataFormatException e) {
            }
        }
        try {
            bos.close();
        } catch (IOException e) {
        }

        // Get the decompressed data
        byte[] decompressedData = bos.toByteArray();

        return decompressedData;


    }

 public static BlobKey putInBlobStore(String contentType, byte[] filebytes) throws IOException {

        // Get a file service
          FileService fileService = FileServiceFactory.getFileService();


          AppEngineFile file = fileService.createNewBlobFile(contentType);

          // Open a channel to write to it
          boolean lock = true;
          FileWriteChannel writeChannel = fileService.openWriteChannel(file, lock);

          // This time we write to the channel using standard Java
          BufferedInputStream in = new BufferedInputStream(new ByteArrayInputStream(filebytes));
          byte[] buffer;
          int defaultBufferSize = 524288;
          if(filebytes.length > defaultBufferSize){
              buffer = new byte[defaultBufferSize]; // 0.5 MB buffers
          }
          else{
              buffer = new byte[filebytes.length]; // buffer the size of the data
          }

            int read;
            while( (read = in.read(buffer)) > 0 ){ //-1 means EndOfStream
                System.out.println(read);
                if(read < defaultBufferSize){
                    buffer = new byte[read];
                }
                ByteBuffer bb = ByteBuffer.wrap(buffer);
                writeChannel.write(bb);
            }
            writeChannel.closeFinally();

        return fileService.getBlobKey(file);
    }
}

在我的 Functions 类中使用静态 compress() 和 putInBlobStore() 函数，我可以像这样压缩和存储一个 byte[]:

BlobKey dataBlobKey =  Functions.putInBlobStore("MULTIPART_FORM_DATA", Functions.compress(orginalDataByteArray));

很甜。我真的很喜欢GAE。

但是现在，问题是:

我正在存储压缩的 HTML，我想即时检索和解压缩以显示在 JSP 页面内的 iframe 中。压缩很快，但解压需要永远!即使压缩后的 HTML 为 15k，有时解压也会死掉。

这是我的解压方法:

 URL file = new URL("/blobserve?key=" + htmlBlobKey);
         URLConnection conn = file.openConnection();
         conn.setReadTimeout(30000);
         conn.setConnectTimeout(30000);
         InputStream inputStream = conn.getInputStream();
         byte[] data = IOUtils.toByteArray(inputStream);
         return new String(Functions.decompress(data));

关于如何最好地从 blobstore 中获取压缩的 HTML、解压缩并显示它有什么想法吗？即使我需要将它传递给任务队列并在显示进度条的同时轮询完成 - 那也没关系。我真的不在乎，只要它有效并且最终有效即可。如果您能在这里与我分享任何指导，我将不胜感激。

感谢您的帮助。

Answer 1

您可以查看运行异步的 RequestBuilder

RequestBuilder requestBuilder = new RequestBuilder(RequestBuilder.GET,"/blobserve?key=" + htmlBlobKey);
try {
requestBuilder.sendRequest(null, new RequestCallback() {
public void onError(Request request, Throwable exception) {
  GWT.log(exception.getMessage());
}
public void onResponseReceived(Request request, Response response) {
  doSomething(response.getText());//here update your iframe and stop progress indicator
}
});
} catch (RequestException ex) {
  GWT.log(ex.getMessage());
}