Netty throws IndexOutOfBoundsException

Question

I am currently working on integrating Netty to a server that will communicate using XML messages. These XML messages are actually objects that has been serialized to XML-messages which are then sent over a TCP connection. I can both send and receive objects, but I get the following exception at the second message I send to the server:

java.lang.IndexOutOfBoundsException: readerIndex(306) + length(613) exceeds writerIndex(614): UnpooledUnsafeDirectByteBuf(ridx: 306, widx: 614, cap: 1024)
    at io.netty.buffer.AbstractByteBuf.checkReadableBytes(AbstractByteBuf.java:1161)
    at io.netty.buffer.AbstractByteBuf.skipBytes(AbstractByteBuf.java:734)
    at io.netty.buffer.WrappedByteBuf.skipBytes(WrappedByteBuf.java:540)
    at io.netty.handler.codec.xml.XmlFrameDecoder.decode(XmlFrameDecoder.java:176)
    at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:227)

I have the following code to initialize the channel:

@Override
public void initChannel(SocketChannel ch) throws Exception {
    LOGGER.info("Accepted connection from " + ch.remoteAddress().toString());
    ClientConnection connection = new ClientConnection(ch);
    ch.pipeline().addLast(new XmlFrameDecoder(6000), connection);
}

And the following code to handle messages I receive:

@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
    LOGGER.info("Got data");
    ByteBuf buf = (ByteBuf)msg;
    try (ByteBufInputStream is = new ByteBufInputStream(buf)) {
        Message message = MessageFactory.getInstance().deserialize(is);
        // does stuff with message...
    } catch (Throwable ex) {
        LOGGER.log(Level.WARNING, ex.getMessage(), ex);
    } finally {
        ReferenceCountUtil.release(msg);
    }
}

And this code for sending messages:

public void sendMessage(Message msg) {
    ByteBufAllocator alloc = PooledByteBufAllocator.DEFAULT;
    ByteBuf buf = alloc.buffer(1024);

    try (ByteBufOutputStream outputStream = new ByteBufOutputStream(buf)) {
        String message = MessageFactory.getInstance().serialize(msg) + "\0";
        outputStream.write(message.getBytes());
        this.socketChannel.writeAndFlush(buf);
    } catch (IOException ex) {
        LOGGER.log(Level.INFO, ex.getMessage(), ex);
    }
}

I am using the java.beans.XMLDecoder and XMLEncoder for the encoding/decoding of the XML objects. As the messages I am sending is 307 in size, I thought that the buffer should be cleared after I have handled a message, however this was not the case. Anyone got any ideas on what may be my problem?

Answer 1

事实证明，问题是XMLEncoder在XML文档的末尾添加了一个\\ n，这在Netty开始读取XML消息时搞砸了。