Netty入門應用

這是一個簡單的時間服務器，當客戶端發來請求的時候，返回當前的時間

public class TimeServer {

    public void bind(int port) throws Exception {
        // 配置服務端的NIO線程組
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap
                    .group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());
            // 綁定端口，同步等待成功
            ChannelFuture channelFuture = serverBootstrap.bind(port).sync();

            // 等待服務端監聽端口關閉
            channelFuture.channel().closeFuture().sync();
        } finally {
            // 優雅退出，釋放線程池資源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel socketChannel) {
            socketChannel.pipeline().addLast(new TimeServerHandler());
        }

    }

    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // 採用默認值
            }
        }
        new TimeServer().bind(port);
    }
}

public class TimeServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("The time server receive order : " + body);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body)
                ? new java.util.Date(System.currentTimeMillis()).toString() : "BAD ORDER";
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

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

代碼主要框架是這樣的

1. 配置服務端的兩個線程組bossGroup workerGroup

2. 通過一系列鏈式調用，構造serverBootstrap

ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap
                    .group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());

3. 設置handler

4. 綁定端口，啓動服務

 

下面看下TimeServerHandler，主要是覆蓋了channelRead方法，表示當服務器接受到信息的時候，將執行的代碼

public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("The time server receive order : " + body);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body)
                ? new java.util.Date(System.currentTimeMillis()).toString() : "BAD ORDER";
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
    }

ByteBuf buf = (ByteBuf) msg; 將消息對象轉換成ByteBuf,ByteBuff類似JDK中的java.nio.ByteBuffer對象，不過更強大

buf.readableBytes() 返回可讀取的字節數目

buf.readBytes(req) 讀取內容到req中

這個時候我們就拿到了客戶端請求的信息並保存到了req數組中了

 

 

下面是Client端代碼

public class TimeClient {

    public void connect(int port, String host) throws Exception {
        // 配置客戶端NIO線程組
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel socketChannel) {
                            socketChannel.pipeline().addLast(new TimeClientHandler());
                        }
                    });

            // 發起異步連接操作
            ChannelFuture channelFuture = bootstrap.connect(host, port).sync();

            // 當代客戶端鏈路關閉
            channelFuture.channel().closeFuture().sync();
        } finally {
            // 優雅退出，釋放NIO線程組
            group.shutdownGracefully();
        }
    }

    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // 採用默認值
            }
        }
        new TimeClient().connect(port, "127.0.0.1");
    }
}

public class TimeClientHandler extends ChannelHandlerAdapter {

    private static final Logger logger = Logger.getLogger(TimeClientHandler.class.getName());

    private final ByteBuf firstMessage;

    /**
     * Creates a client-side handler.
     */
    public TimeClientHandler() {
        byte[] req = "QUERY TIME ORDER".getBytes();
        firstMessage = Unpooled.buffer(req.length);
        firstMessage.writeBytes(req);

    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(firstMessage);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("Now is : " + body);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // 釋放資源
        logger.warning("Unexpected exception from downstream : " + cause.getMessage());
        ctx.close();
    }
}

除了編寫代碼來實現客戶端之外，我們還可以使用linux的telnet命令

telnet localhsot 8080

 

服務端將接受到客戶端的信息並且打印出來