import com.vaadin.server.DownloadStream; //导入依赖的package包/类
/**
 * Gets the stream.
 *
 * @return the stream
 */
/*
 * (non-Javadoc)
 * 
 * @see com.vaadin.terminal.StreamResource#getStream()
 */
@Override
public DownloadStream getStream() {
	final DownloadStream stream = new DownloadStream(getStreamSource().getStream(), this.contentType,
			this.filename);
	stream.setParameter("Content-Disposition", "attachment;filename=" + this.filename);
	// This magic incantation should prevent anyone from caching the data
	stream.setParameter("Cache-Control", "private,no-cache,no-store");
	// In theory <=0 disables caching. In practice Chrome, Safari (and,
	// apparently, IE) all
	// ignore <=0. Set to 1s
	stream.setCacheTime(1000);

	return stream;
}
 

import com.vaadin.server.DownloadStream; //导入依赖的package包/类
public FileResource createFileResource(File file) 
 {
     return new FileResource(file) 
     {
private static final long serialVersionUID = -4183674760353232866L;

@Override
         public DownloadStream getStream() 
         {
             try 
             {
                 final DownloadStream ds = new DownloadStream(new FileInputStream(getSourceFile()), getMIMEType(), getFilename());
                 ds.setParameter("Content-Length", String.valueOf(getSourceFile().length()));
                 ds.setCacheTime(getCacheTime());
                 
                 return ds;
             } 
             catch (final FileNotFoundException e) 
             {
                 return null;
             }//end try-catch block...                
         }//end method...
     };        
 }
 

import com.vaadin.server.DownloadStream; //导入依赖的package包/类
@Override
public DownloadStream getStream() {
    DownloadStream download = new DownloadStream(super.getStreamSource().getStream(),contentType,fileName);
    download.setCacheTime(2000);
    return download;
}
 

import com.vaadin.server.DownloadStream; //导入依赖的package包/类
@Override
public DownloadStream getStream()
{
	final StreamSource ss = getStreamSource();

	PartialDownloadStream ds = new PartialDownloadStream(null, getMIMEType(), getFilename());

	if (ss != null)
	{
		try
		{
			long contentLength = contentLengthProvider.getContentLength();
			ds.setStream(ss.getStream());
			ds.setContentLength(contentLength);
			ds.setParameter("Content-Length", String.valueOf(contentLength));
			ds.setBufferSize(getBufferSize());
			ds.setCacheTime(getCacheTime());

		}
		catch (final Exception e)
		{
			logger.error(e, e);
			if (ui != null)
			{
				ui.access(new Runnable()
				{

					@Override
					public void run()
					{
						Notification.show(e.getMessage(), Type.ERROR_MESSAGE);

					}
				});
			}
			else
			{
				ErrorWindow.showErrorWindow(e);
			}

		}
	}
	return ds;
}