深入学习netty系列(1)

一、Server端的编程模型

• 示例代码1

EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
     ServerBootstrap b = new ServerBootstrap();
     b.group(bossGroup, workerGroup)
      .channel(NioServerSocketChannel.class)
      .handler(new LoggingHandler(LogLevel.INFO))
      .childHandler(new ChannelInitializer<SocketChannel>(){
          @Override
           public void initChannel(SocketChannel ch) throws Exception {
               ChannelPipeline p = ch.pipeline();

               p.addLast(new TimeServerHandler());
           }
      });
      b.bind(PORT).sync().channel().closeFuture().sync();
} finally {
      bossGroup.shutdownGracefully();
      workerGroup.shutdownGracefully();

}

由ServerBootstrap作为入口，用链式编程方式，分别调用group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 100).handler().

childHander()方法相当重要的方法，开发人员入手的地方，采用面向接口的方式，让开发人实现ChannelInitializer接口,实现initChannel(SocketChannel ch)方法，把自己的Handler通过channelPipeline().addLast(new TimeServerHandler())来实现事件处理。

• 示例代码2

@Sharable
public class TimeServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(final ChannelHandlerContext ctx) {
    	 final ByteBuf time = ctx.alloc().buffer(4); // (2)
         time.writeInt((int) (System.currentTimeMillis() / 1000L + 2208988800L));

         final ChannelFuture f = ctx.writeAndFlush(time); // (3)
         f.addListener(new ChannelFutureListener() {
             @Override
             public void operationComplete(ChannelFuture future) {
                 assert f == future;
                 ctx.close();
             }
         }); // (4)
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

二、client编程模型

• 代码示例3

public class TimeClient {

	public static void main(String[] args) throws Exception {
            new TimeClient().bind();
        }

	private void bind() throws InterruptedException{
        String host = "localhost";
        int port = Integer.parseInt("8080");
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            Bootstrap b = new Bootstrap(); // (1)
            b.group(workerGroup); // (2)
            b.channel(NioSocketChannel.class); // (3)
            b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
            b.handler(new channelHandler());

            // 启动客户端
            ChannelFuture f = b.connect(host, port).sync(); // (5)

            // 等待连接关闭
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }
	}

	private class channelHandler extends ChannelInitializer<SocketChannel>{
		@Override
		protected void initChannel(SocketChannel ch) throws Exception {
			ch.pipeline().addLast(new TimeClientHandler());
		}
	}
}

public class TimeClientHandler extends ChannelInboundHandlerAdapter {

    private static final SimpleDateFormat sdf = new SimpleDateFormat("yy-MM-dd HH:mm:ss");
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ByteBuf m = (ByteBuf) msg; // (1)
        try {
            long currentTimeMillis = (m.readUnsignedInt() - 2208988800L) * 1000L;
            System.out.println(sdf.format(new Date(currentTimeMillis)));
            ctx.close();
        } finally {
            m.release();
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}