Java Netty 学习笔记（二）使用Netty编程-蒲公英云

Java Netty 学习笔记（二）使用Netty编程

电玩女神 2022-06-15 02:53 276阅读 0赞

熟悉了使用java nio编程的套路，实际上就跟底层socket的没啥区别。
下面学习如何使用Netty编写简单的Time Server。
代码：https://github.com/NearXdu/NettyLearn

public class TimeServer {
    public void bind(int port) throws Exception{
        //配置服务端的NIO线程组
        //
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try{
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG,1024)
                    .childHandler(new ChildChannelHandler());
            //绑定端口，同步等待成功
            ChannelFuture f = b.bind(port).sync();
            //等待服务端监听端口关闭
            f.channel().closeFuture().sync();
        }finally {
            //释放线程池资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel ch) throws Exception {
            ch.pipeline().addLast(new TimeServerHandler());
        }
    }
    public static void main(String[] args) throws Exception{
        int port =1025;
        if(args!=null && args.length>0){
            try{
                port =Integer.valueOf(args[0]);
            }catch (NumberFormatException e){
            }
        }
        new TimeServer().bind(port);
    }
}

1.NioEventLoopGroup:Reactor线程组，用于处理网络事件。
2.ServerBootstrap:Netty用于启动NIO服务端的辅助启动类。
3.ServerBootstrap的group方法设置监听套接字NioServerSocketChannel
设置BACKLOG，设置IO事件的处理类ChildChannelHandler
4.ServerBootstrap的bind方法绑定监听端口

在Handler类中，有些区别就是netty4和netty5的API会有些出入，在书中继承ChannelHandlerAdapter，我用的是Netty4,因此需要稍微改写：

public class TimeServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        ByteBuf buf = (ByteBuf) msg;//read buff
        byte[] req = new byte[buf.readableBytes()];//通过readble获取到大小
        buf.readBytes(req);//readByte将数据塞入req中
    //业务
        String body = new String(req, "UTF-8");
        System.out.println("The time server receive order : " + body);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body.trim()) ? new java.util.Date(
                System.currentTimeMillis()).toString() : "BAD ORDER";
    //构造响应
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
    //发送
        ctx.write(resp);
    }
}