异步通信框架Netty之ChannelHandlerAdapter探究

注：本文基于Netty 5.x版本

ChannelHandlerAdapter 处于io.netty.channel包下

探究执行顺序

• 服务器启动，等待客户端连接；
• 客户端连接 发送一条消息；
• 此时服务器接收到消息，发送“Received your message !\n”表示已接收到；
• 客户端关闭链接

public class HelloServerHandler extends ChannelHandlerAdapter {

	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		System.err.println("channelActive");
		ctx.writeAndFlush("Welcome to "
				+ InetAddress.getLocalHost().getHostName() + " service!\n");
		super.channelActive(ctx);
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg)
			throws Exception {

		System.err.println("channelRead");
		// 返回客户端消息 - 我已经接收到了你的消息
		ctx.writeAndFlush("Received your message !\n");

	}

	@Override
	public void channelInactive(ChannelHandlerContext ctx) throws Exception {
		System.err.println("channelInactive");
		super.channelInactive(ctx);
	}

	@Override
	public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
		System.err.println("handlerAdded");
		super.handlerAdded(ctx);
	}

	@Override
	public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
		System.err.println("handlerRemoved");
		super.handlerRemoved(ctx);
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
			throws Exception {
		System.err.println("exceptionCaught");
		super.exceptionCaught(ctx, cause);
	}

	@Override
	public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
		System.err.println("channelRegistered");
		super.channelRegistered(ctx);
	}

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

	@Override
	public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
			throws Exception {
		System.err.println("userEventTriggered");
		super.userEventTriggered(ctx, evt);
	}

	@Override
	public void channelWritabilityChanged(ChannelHandlerContext ctx)
			throws Exception {
		System.err.println("channelWritabilityChanged");
		super.channelWritabilityChanged(ctx);
	}

	@Override
	public void bind(ChannelHandlerContext ctx, SocketAddress localAddress,
			ChannelPromise promise) throws Exception {
		System.err.println("bind");
		super.bind(ctx, localAddress, promise);
	}

	@Override
	public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress,
			SocketAddress localAddress, ChannelPromise promise)
			throws Exception {
		System.err.println("connect");
		super.connect(ctx, remoteAddress, localAddress, promise);
	}

	@Override
	public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise)
			throws Exception {
		System.err.println("disconnect");
		super.disconnect(ctx, promise);
	}

	@Override
	public void close(ChannelHandlerContext ctx, ChannelPromise promise)
			throws Exception {
		System.err.println("close");
		super.close(ctx, promise);
	}

	@Override
	public void read(ChannelHandlerContext ctx) throws Exception {
		System.err.println("read");
		super.read(ctx);
	}

	@Override
	public void write(ChannelHandlerContext ctx, Object msg,
			ChannelPromise promise) throws Exception {
		System.err.println("write");
		super.write(ctx, msg, promise);
	}

	@Override
	public void flush(ChannelHandlerContext ctx) throws Exception {
		System.err.println("flush");
		super.flush(ctx);
	}

}

服务器控制台打印结果:

handlerAdded
channelRegistered
channelActive
read
channelRead
channelReadComplete
read
channelReadComplete
read
exceptionCaught
channelInactive
handlerRemoved

To Be Continued