Netty：如何确定文件是否已完整发送？

Question

我试图从java服务器应用程序发送文件（pdf/bpm/jpg/png）到java客户端应用程序。 该文件以块形式发送。但是，如何知道文件何时完全发送？

我的第一个想法是使用得到通知，如果文件已完全发送。但是由于它在文件仍在发送时也被触发，所以它是无用的。有关如何进行的任何建议？

客户端管道：

ChannelPipeline p = ch.pipeline(); 
p.addLast("FileChunkHandler", new FileChunkHandler()); 

服务器管道：

p.addLast("Encoder", new ObjectEncoder()); 
p.addLast("Decoder", new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.cacheDisabled(null))); 
p.addLast("chunkedWriteHandler", new ChunkedWriteHandler()); 
p.addLast("FileSenderHandler", new FileSenderHandler()); 

的FileChunkHandler在客户端：

public class FileChunkHandler extends SimpleChannelInboundHandler<ChunkedFile>{ 
    private ObjectOutputStream oout = null; 

    @Override protected void channelRead0(ChannelHandlerContext ctx, ChunkedFile msg) throws Exception{ 
     System.out.println("channelRead0"); 

     if (oout == null){ 
      FileOutputStream out = new FileOutputStream("/Users/user/Documents/tmp/test/bla.txt"); 
      oout = new ObjectOutputStream(out); 
     } 

     ByteBuf buf = (ByteBuf)msg; 
     int numberOfReadableBytes = buf.readableBytes(); 
     byte[] bytes = new byte[numberOfReadableBytes]; 
     buf.readBytes(bytes); 

     oout.write(bytes, 0, bytes.length); 
    } 

    @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception{ 
     System.out.println("channelReadComplete"); 
     ctx.fireChannelReadComplete(); 
    } 
} 

的FileSenderHandler在服务器上：

公共类FileSenderHandler扩展ChannelInboundHandlerAdapter {

@Override public void channelRegistered(ChannelHandlerContext ctx) throws Exception{ 

    File file = new File("/Users/user/Documents/tmp/test/test.txt"); 

    RandomAccessFile raf = new RandomAccessFile(file, "r"); 
    ChannelFuture sendFileFuture = null; 

    if (ctx.pipeline().get(SslHandler.class) == null) { 
     sendFileFuture = ctx.write(new DefaultFileRegion(raf.getChannel(), 0, raf.length()), ctx.newProgressivePromise()); 
     ctx.flush(); 
    } else { 
     sendFileFuture = ctx.writeAndFlush(file, ctx.newProgressivePromise()); 
    } 

    sendFileFuture.addListener(new ChannelProgressiveFutureListener() { 
     @Override 
     public void operationProgressed(ChannelProgressiveFuture future, long progress, long total) { 
      if (total < 0) { // total unknown 
       System.err.println(future.channel() + " Transfer progress: " + progress); 
      } else { 
       System.err.println(future.channel() + " Transfer progress: " + progress + "/" + total); 
      } 
     } 

     @Override 
     public void operationComplete(ChannelProgressiveFuture future) { 
      System.err.println(future.channel() + " Transfer complete."); 
     } 
    }); 

    ctx.fireChannelRegistered(); 
} 

Answer 1

让您的客户端和服务器通过套接字comunicate。当客户端向服务器发送文件时，服务器应向客户端发送“文件已接收消息”。

Google“用Java发送套接字消息”中，有很多示例。

希望它有帮助。

Answer 2

我解决了这个问题（但我还没完全满意）。欢迎进一步的反馈！

我正在创建一个FileStatusHandler，它接收一个包含文件信息（如长度和名称）的模型。这些信息作为参数传递给FileDecoder，该FileDecoder被添加到管道中。

public class FileStatusHandler extends SimpleChannelInboundHandler<FileInformationModel>{ 

@Override protected void channelRead0(ChannelHandlerContext ctx, FileInformationModel msg) throws Exception{ 
    String name = "out_" +msg.getName(); 
    long length = msg.getLength(); 

    FileDecoder fileDecoder = new FileDecoder(length, name); 
    ctx.pipeline().addFirst(CommonClientDefines.Handler.FILE_DECODER, fileDecoder); 

    ctx.writeAndFlush(CommonClientDefines.READY_FOR_CONTENT); 
} 
} 

FileDecoder本身负责接收文件内容，并在收到文件时删除处理程序。

public class FileDecoder extends MessageToMessageDecoder<ByteBuf>{ 

private final String name; 
private final long length; 
private FileChannel fileChannel; 
private long receivedLength = 0; 

public FileDecoder(long length, String name) throws IOException{ 
    this.length = length; 
    this.name = name; 

    Path directoryPath = Paths.get(System.getProperty("user.home"), "Download", "tmp", "test"); 
    Path filePath = directoryPath.resolve(name); 
    fileChannel = FileChannel.open(filePath, StandardOpenOption.CREATE, StandardOpenOption.WRITE); 
} 

@Override protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception{ 
    receivedLength += msg.readableBytes(); 
    fileChannel.write(msg.nioBuffer()); 

    if(receivedLength >= length){ 
     fileChannel.close(); 
     ctx.pipeline().remove(CommonClientDefines.Handler.FILE_DECODER); 
    } 
} 
}