我已经使用 Netty 3.3.1-Final 3 周了。我的协议有 3 个步骤，每个步骤都需要不同的FrameDecoder：
- 阅读论据
- 传输一些数据
- 数据管道相互关闭
我经历了很多我无法理解的“阻塞”问题。终于在我看来，阅读org.jboss.netty.example.portunification示例时，我在尝试动态更改我的 FrameDecoder时遇到了一些缓冲区问题：一个 FrameDecoder 的缓冲区（可能）在更改下一个时不是空的。 ..
有没有办法在 Netty 中轻松做到这一点？我必须更改我的协议吗？我需要编写一个大的 FrameDecoder 并管理一个状态吗？如果是这样，如何避免具有公共子部分的不同协议之间的代码重复（例如“读取参数”）？
今天我想到了一个FrameDecoderUnifier（下面的代码）的想法，目的是热添加和删除一些FrameDecoder，你怎么看？
谢谢你的帮助！
雷诺
----------- FrameDecoderUnifier 类 --------------
/**
* This FrameDecoder is able to forward the unused bytes from one decoder to the next one. It provides
* a safe way to replace a FrameDecoder inside a Pipeline.
* It is not safe to just add and remove FrameDecoder dynamically from a Pipeline because there is a risk
* of unread bytes inside the buffer of the FrameDecoder you wan't to remove.
*/
public class FrameDecoderUnifier extends FrameDecoder {
private final Method frameDecoderDecodeMethod;
volatile boolean skip = false;
LastFrameEventHandler eventHandler;
LinkedList<Entry> entries;
Entry entry = null;
public FrameDecoderUnifier(LastFrameEventHandler eventHandler) {
this.eventHandler = eventHandler;
this.entries = new LinkedList<Entry>();
try {
this.frameDecoderDecodeMethod = FrameDecoder.class.getMethod("decode", ChannelHandlerContext.class, Channel.class, ChannelBuffer.class);
} catch (NoSuchMethodException ex) {
throw new RuntimeException(ex);
} catch (SecurityException ex) {
throw new RuntimeException(ex);
}
}
public void addLast(FrameDecoder decoder, LastFrameIdentifier identifier) {
entries.addLast(new Entry(decoder, identifier));
}
private Object callDecode(FrameDecoder decoder, ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
return frameDecoderDecodeMethod.invoke(decoder, ctx, channel, buffer);
}
@Override
protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
if (entry == null && !entries.isEmpty()) {
entry = entries.getFirst();
}
if (entry == null) {
return buffer; //No framing, no decoding
}
//Perform the decode operation
Object obj = callDecode(entry.getDecoder(), ctx, channel, buffer);
if (obj != null && entry.getIdentifier().isLastFrame(obj)) {
//Fire event
eventHandler.lastObjectDecoded(entry.getDecoder(), obj);
entry = null;
}
return obj;
}
/**
* You can use this interface to take some action when the current decoder is changed for the next one.
* This can be useful to change some upper Handler in the pipeline.
*/
public interface LastFrameEventHandler {
public void lastObjectDecoded(FrameDecoder decoder, Object obj);
}
public interface LastFrameIdentifier {
/**
* True if after this frame, we should disable this decoder.
* @param obj
* @return
*/
public abstract boolean isLastFrame(Object decodedObj);
}
private class Entry {
FrameDecoder decoder;
LastFrameIdentifier identifier;
public Entry(FrameDecoder decoder, LastFrameIdentifier identifier) {
this.decoder = decoder;
this.identifier = identifier;
}
public FrameDecoder getDecoder() {
return decoder;
}
public LastFrameIdentifier getIdentifier() {
return identifier;
}
}
}