netty server端基本使用框架梳理

    public static void main(String[] arg)throws Exception{
        //NioEventLoopGroup 死循环
        //netty的服务器会启动两个服务器，boss来接收连接，worker用来处理连接及响应。
        //本质上都是nio的异步处理的事件循环对象
        EventLoopGroup bossG = new NioEventLoopGroup();
        EventLoopGroup workerG = new NioEventLoopGroup();
        try {
            //启动服务器，ServerBootstrap辅助启动封装类
            //ServerBootstrap里面封装了netty的相关属性和方法，简化netty服务器的创建工作
            ServerBootstrap bootstrap = new ServerBootstrap();
            //方法链形式（返回对象），装配启动类属性
            bootstrap.group(bossG, workerG)
                    .channel(NioServerSocketChannel.class)//netty里对nio的ServerSocketChannel进行了封装
                    .childHandler(new TestServerInitializer());//childHandler针对worker，用来处理交给woeker的连接
            //服务器真正启动，
            //sync（阻塞方法）用来等待和同步连接
            //返回ChannelFuture集成Future，调用异步方法后直接返回Future，里面方法可判断异步操作是否结束
            ChannelFuture channelFuture = bootstrap.bind(8899).sync();
            //netty关闭操作
            channelFuture.channel().closeFuture().sync();
        }finally{
            //netty优雅关闭？
            //如果关闭的时候有连接还没处理，在可控的时间里，把连接处理完，并不接受新的连接
            bossG.shutdownGracefully();
            workerG.shutdownGracefully();
        }
    }

public class TestServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    public void initChannel(SocketChannel ch) throws Exception{
        //获得channel的管道，可添加编解码器，可用netty提供方法或自定义
        //请求处理类TestServerHandler
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("httpServerCodec",new HttpServerCodec());
        pipeline.addLast("testServerHandler",new TestServerHandler());
    }
}

//SimpleChannelInboundHandler,入栈，数据从外边进来。SimpleChannelOutboundHandler，出栈，把数据发到客户端，
public class TestServerHandler extends SimpleChannelInboundHandler<HttpObject> {

    //ChannelHandlerContext 消息对象，HttpObject 请求对象，真正传入的数据类型
    //连接进来时  handlerAdded-》channelRegistered-》channelActive-》channelRead0-》channelInactive-》channelUnregistered
    @Override
    public void channelRead0(ChannelHandlerContext ctx,HttpObject msg)throws Exception{
        if(msg instanceof HttpRequest){
            out.println("remote address:"+ctx.channel().remoteAddress());
            URI url = new URI(((HttpRequest) msg).uri());
            if(url.getPath().equals("/favicon.ico")){
                   out.println("from brows " );
                   out.println(((HttpRequest) msg).method());
            }
            ByteBuf content = Unpooled.copiedBuffer("Hello World", CharsetUtil.UTF_8);
            FullHttpResponse res = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1
                    , HttpResponseStatus.OK,content);
            res.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain");
            res.headers().set(HttpHeaderNames.CONTENT_LENGTH,content.readableBytes());

            ctx.writeAndFlush(res);
            ctx.channel().close();
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx)throws Exception{
        out.println("channel active");
        super.channelActive(ctx);
    }

    @Override
    public void channelRegistered(ChannelHandlerContext ctx)throws Exception{
        out.println("channel registered");
        super.channelRegistered(ctx);
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception{
        out.println("handler added");
        super.handlerAdded(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx)throws Exception{
        out.println("channel inactive");
        super.channelInactive(ctx);
    }

    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
        out.println("channel unregistered");
        super.channelUnregistered(ctx);
    }

}