netty-第一個案例

netty-第一個demo

搭建環境

maven引入

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.12.Final</version>
</dependency>

服務端

Netty 服務器都需要以下兩部分

• 至少一個 ChannelHandler — 該組件實現了服務器對從客戶端接收的數據的處理，即它的業務邏輯。
• 引導 — 這是配置服務器的啓動代碼。至少，它會將服務器綁定到它要監聽連接請求的端口上

channelHandler

@Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {
    // 對於每個傳入的消息都要調用
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in = (ByteBuf) msg;
        System.out.println("server recevied:"+ in.toString(StandardCharsets.UTF_8));
        ctx.write(in);
    }
    // 通知ChannelInboundHandler最後一次對channel-
    //Read()的調用是當前批量讀取中的最後一條消息
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
    }

    // 在讀取操作期間，有異常拋出時會調用

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("讀取操作錯誤信息");
        cause.printStackTrace(); //打印錯誤
        ctx.close();//關閉channel
    }
}

BootStrap

public class EchoServer {

    private final int port;

    public EchoServer(int port) {
        this.port = port;
    }

    public static void main(String[] args) throws InterruptedException {
        int port = Integer.parseInt("1234");
        new EchoServer(port).start();
    }
    
//綁定到服務器將在其上監聽並接受傳入連接請求的端口；
//配置 Channel ，以將有關的入站消息通知給 EchoServerHandler 實例
    private void start() throws InterruptedException {
        final EchoServerHandler serverHandler = new EchoServerHandler();
        NioEventLoopGroup group = new NioEventLoopGroup();

        try {
        ServerBootstrap b  = new ServerBootstrap(); //創建bootstrap
        b.group(group)
                .channel(NioServerSocketChannel.class) //使用nio傳輸channel
                .localAddress(port)  // 綁定端口
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    // 添加一個EchoServer-
                    //Handler 到子Channel
                    //的 ChannelPipeline
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
                ch.pipeline().addLast(serverHandler);
                // EchoServerHandler被標註爲@Shareable，所以我們可以總是使用同樣的實例
            }
        });

//	異步地綁定服務器；調用 sync()方法阻塞等待直到綁定完成
            ChannelFuture f = b.bind().sync();
//            獲取 Channel 的CloseFuture，並且阻塞當前線程直到它完成
            f.channel().closeFuture().sync();

        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            group.shutdownGracefully().sync();
        }
    }
}

客戶端

EchoClientHandler

@Sharable
public class EchoClientHandler
    extends SimpleChannelInboundHandler<ByteBuf> {
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!",
                CharsetUtil.UTF_8));
    }

    @Override
    public void channelRead0(ChannelHandlerContext ctx, ByteBuf in) {
        System.out.println(
                "Client received: " + in.toString(CharsetUtil.UTF_8));
    }

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

BootStrap

public class EchoClient {
    private final String host;
    private final int port;


    public EchoClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public static void main(String[] args) throws InterruptedException {
        final String host = "127.0.0.1";
        final int port = Integer.parseInt("1234");
        new EchoClient(host, port).start();
    }

    private void start() throws InterruptedException {
        NioEventLoopGroup group = new NioEventLoopGroup();
        try {
        Bootstrap b = new Bootstrap();

        b.group(group)
                .channel(NioSocketChannel.class)
                .remoteAddress(host,port)
                .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {

                ch.pipeline().addLast(new EchoClientHandler());

            }
        });


            ChannelFuture future = b.connect().sync();
            future.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            group.shutdownGracefully().sync();
        }

    }
}

運行

• 先啓動服務端
• 再啓動客戶端

服務端結果

server recevied:Netty Socket!

[外鏈圖片轉存失敗,源站可能有防盜鏈機制,建議將圖片保存下來直接上傳(img-NoEjY2Eb-1571234128207)(C:\Users\ronny\OneDrive\筆記\高併發\picture\1571232070255.png)]

參考文檔

[Netty 拆包粘包和服務啓動流程分析](https://segmentfault.com/a/1190000013039327)

Netty序章之BIO NIO AIO演變

java nio與bio —— 阻塞IO與非阻塞IO的區別

Java實戰之從同步阻塞IO到NIO

netty實戰