Netty 3.5.8-Final - Help on FrameDecoder

Question

我的帧解码器有以下代码：

protected Object decode(ChannelHandlerContext channelHandlerContext,
        Channel channel, ChannelBuffer channelBuffer) throws Exception {
    //Header 1 + 4 length bytes
    if (channelBuffer.readableBytes() < 5) {
        return null;
    }
    System.out.println(channelBuffer.readerIndex());
    //mark the reader index
    channelBuffer.markReaderIndex();
    //extract the length bytes and convert to an int value 
    //**note: length value of the message is a decimal not hex
    StringBuilder lengthBuilder = new StringBuilder("");
    for (int ctr = 1; ctr < 5; ctr += 1) {
        lengthBuilder.append(String.format("%02x",
                channelBuffer.getByte(ctr)));
    }
    int length = Integer.parseInt(hexToASCII(lengthBuilder.toString()));
    System.out.println("This is the length: " + length);
    System.out.println("reader index: " + channelBuffer.readerIndex());
            channelBuffer.readerIndex(4);
    //get the remaining bytes
    if (channelBuffer.readableBytes() <= length) {
        channelBuffer.resetReaderIndex();
        return null;
    }
    String s = "";
    for (int ctr = 0; ctr < length + 5; ctr += 1) {
        s += (char) channelBuffer.getByte(ctr);
    }
    return s;
}

一切都很顺利，直到int length = Integer.parseInt(hexToASCII(lengthBuilder.toString()));线。在该行之后，解码器仍然可以读取剩余的字节，但它现在使用实际消息作为长度字段，生成解析异常错误。

说，我有一条消息B0005EHELLO [B is the header] [0005 - actual message length] [E - header 2] [HELLO - actual message]的地方..将长度字段解析为整数值后，解码器使用实际消息的前四个字母HELL来分析长度字段，并生成异常。请帮助我解决这个问题。

Answer 1

通过将读取器索引从 4 更改为 5 来修复。

channelBuffer.readerIndex(4);

我还在返回结果之前添加了读取器索引重置，以便它将读取整个消息，而不仅仅是实际的消息:)

channelBuffer.readerIndex(0);
String s = "";
for (int ctr = 0; ctr < length + 5; ctr += 1) {
    s += (char) channelBuffer.getByte(ctr);
}