Nettty入門（一）

Netty常用類介紹

1. Bootstrap類，Bootstrap是Netty應用程序的啓動類，我們可以通過其指定採用某種Channel,以及處理IO操作的EventLoopgroup,同時還可以指定我們需要操作的handler.
2. 一個EventLoop可以爲多個Channel服務,EventLoopGroup會包含多個EventLoop。
3. ChannelInitializer 類中提供了ChannelPipeLine，我們可以通過這個類進行攔截，處理某個時間，ChannelPipeLine還可以指定我們對傳輸的信息進行那種編碼，解碼，以及怎樣處理各種事件
4. Handler類，我們通常是繼承ChannelInboundHandlerAdapter來重寫channelActive（連接成功調用），channelRead（當消息來的時候調用）,exceptionCaught（發生異常時調用）等方法。
5. Future和ChannelFutures。可以通過註冊一個監聽，當操作執行成功或失敗時監聽會自動觸發。

netty jar包下載

簡單的列子

客戶端

public class NettyClient {
private String address;
private int port;
public NettyClient(String address,int port){
    this.address=address;
    this.port=port;
}
public void start(){
    EventLoopGroup group=new NioEventLoopGroup();
    Bootstrap bootstrap=new Bootstrap().group(group).channel(NioSocketChannel.class).handler(new ClientChannelInitializer());
    try {
        Channel channel=bootstrap.connect(address,port).sync().channel();
        while(true){
            String str=new Scanner(System.in).next();
            channel.writeAndFlush(str);
        }
    } catch (InterruptedException e) {
        e.printStackTrace();
    }finally {
        group.shutdownGracefully();
    }
}

ChannelInitializer類的實現（主要是指定連接的編碼，解碼處理事件的handler）

public class ClientChannelInitializer extends ChannelInitializer<SocketChannel> {

protected void initChannel(SocketChannel socketChannel) throws Exception {
    ChannelPipeline pipeline=socketChannel.pipeline();
    pipeline.addLast("encoder",new StringEncoder());
    pipeline.addLast("decoder",new StringDecoder());
    pipeline.addLast("handler",new ClientHandler());
}
}

Handler類的實現（主要定義一些事件的處理）

public class ClientHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
    System.out.println("客戶端連接成功");
}

@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
    System.out.println("客戶端斷開連接");
}

@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
   System.out.println(msg.toString());
}
}

服務端

public class NettyServer {
private int port;
public NettyServer(int port){
    this.port=port;
}
public void startServer(){
    EventLoopGroup bossGroup=new NioEventLoopGroup();
    EventLoopGroup workGroup=new NioEventLoopGroup();
    ServerBootstrap serverBootstrap=new ServerBootstrap().group(bossGroup,workGroup)
            .channel(NioServerSocketChannel.class)
            .childHandler(new ServerChannelInitializer());
    try {
        ChannelFuture future=serverBootstrap.bind(port).sync();
        future.channel().closeFuture().sync();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}
}

服務端的ChannelInitializer類

public class ServerChannelInitializer extends ChannelInitializer<SocketChannel> {
protected void initChannel(SocketChannel socketChannel) throws Exception {
    ChannelPipeline pipeline=socketChannel.pipeline();
    pipeline.addLast("encoder",new StringEncoder());
    pipeline.addLast("decoder",new StringDecoder());
    pipeline.addLast("handler",new ServerHandler());
}
}

服務端的Handler類

public class ServerHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    System.out.println(ctx.channel().remoteAddress()+" "+msg.toString());
    ctx.write("已收到消息");
    ctx.flush();
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    System.out.println(cause.toString());
    ctx.close();
}
}

我也是在學習，如果有錯誤的，請提出來，一起進步，一起學習