BIO、NIO、selector、Netty代码Demo示例

文章目录

- （一）BIO（Blocking I/O 阻塞I/O）
- （二）NIO（Non-Blocking I/O 非阻塞I/O）
- （三）IO多路复用--Selector
- （四）Netty

（一）BIO（Blocking I/O 阻塞I/O）

阻塞I/O的连接accept()方法及数据读取的read()方法都是阻塞的，也就是说没有客户端发起连接时会阻塞，客户端发起连接后不发送数据也会阻塞。

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;
 
/**
* 阻塞IO
*/
public class BioServerDemo {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(9000);
        while(true){
            System.out.println("等待连接。。");
            //阻塞方法
            //可以通过控制台输入命令进行连接：telnet localhost 9000，CTRL+]进入Telnet指令
            Socket clientSocket = serverSocket.accept();
            System.out.println("有客户端连接了。。");
            //虽然采用多线程可以支持多个线程同时访问，但是会引发C10K问题
            //C10K->connection=1w，C10M->connection=1000w，就是连接数很多的意思
            //new Thread(new Runnable() {
            //	@Override
            //	public void run() {
	        //		try {
            			handler(clientSocket);
            //		} catch (IOException e) {
            //			e.printStackTrace();
            //		}
            //	}
            //}).start();
        }
    }
 
    private static void handler(Socket clientSocket) throws IOException {
        byte[] bytes = new byte[1024];
        System.out.println("准备read。。");
		//接收客户端的数据，阻塞方法，客户端没有发送数据，服务端就会没有数据可读时就阻塞
        int read  = clientSocket.getInputStream().read(bytes);
        System.out.println("read完毕。。");
        if (read !=-1){
            System.out.println("接收客户端的数据："+new String(bytes,0,read));
        }
		//clientSocket.getOutputStream().write("HelloClint".getBytes(StandardCharsets.UTF_8));
		//clientSocket.getOutputStream().flush();
    }
}

（二）NIO（Non-Blocking I/O 非阻塞I/O）

非阻塞I/O在客户端连接方法accept()和read()方法中都不会阻塞，我们可以通过返回值判断是否有客户端发起连接或者发送数据，进行相应的处理。
简单的NIO因为是通过遍历的方式，会有大量的空循环

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
 
/**
 *初版- NIO（非阻塞）编程
 */
public class NioServer {
    static List<SocketChannel> channelList = new ArrayList<>();
    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(9000));
        //这里可选非阻塞和阻塞，如果选择阻塞true，下面的accept()方法会阻塞线程
        serverSocketChannel.configureBlocking(false);
        System.out.println("服务启动成功");
        while (true){
            SocketChannel socketChannel = serverSocketChannel.accept();
           if(socketChannel!=null){
               System.out.println("连接成功");
        		//这里可选非阻塞和阻塞，如果选择阻塞true，下面的read()方法会阻塞线程
               socketChannel.configureBlocking(false);
               //将所有连接channel交给一个集合进行管理
               channelList.add(socketChannel);
           }
			//问题点： 空循环时间耗时太久
           Iterator<SocketChannel> iterator = channelList.iterator();
           //遍历访问所有channel集合获取客户端发送的数据，如果有任何一个连接客户端发送了数据，那么就处理当前channel里的数据
           while (iterator.hasNext()){
               SocketChannel sc = iterator.next();
               ByteBuffer byteBuffer = ByteBuffer.allocate(128);
               int len = sc.read(byteBuffer);
               if (len>0){
                   System.out.println("接收到消息："+new String(byteBuffer.array()));
               }else if(len ==-1){
                   iterator.remove();
                   System.out.println("客户端断开连接");
               }
           }
        }
    }
}

（三）IO多路复用–Selector

通过一个多路复用器selector对channel进行管理，这样

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;
/**
 *进阶版- NIO（非阻塞）编程
 * 这是netty和Redis的雏形
 */
public class NioSelectorServer {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(9000));
        serverSocketChannel.configureBlocking(false);
       //启用epoll模型
        Selector selector = Selector.open();
       //注册阻塞事件：创建连接
        SelectionKey selectionKey = serverSocketChannel.register(selector,SelectionKey.OP_ACCEPT);
        System.out.println("服务启动成功");
        while (true){
       		//阻塞等待需要处理的事件发生，这个时候的事件是等待连接
            selector.select();
       		//获取阻塞的事件
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
       		//对阻塞事件进行遍历
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            if(iterator.hasNext()){
                SelectionKey key =iterator.next();
                if(key.isAcceptable()){//这里只针对连接事件，
                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    SocketChannel socketChannel = server.accept();
                    socketChannel.configureBlocking(false);
                    //连接建立后，注册阻塞事件：读取数据
                    SelectionKey selKey = socketChannel.register(selector,SelectionKey.OP_READ);
                }else if(key.isReadable()){//这里只针对read事件，有需要可以针对write事件处理
                    SocketChannel socketChannel = (SocketChannel) key.channel();
                    ByteBuffer byteBuffer = ByteBuffer.allocate(128);
                    socketChannel.configureBlocking(false);
                    int len  = socketChannel.read(byteBuffer);
                    if(len >0 ){
                        System.out.println("接收到消息："+new String(byteBuffer.array()));
                    }else if(len ==-1 )
                    	//关闭socket
                        socketChannel.close();
                        System.out.println("接收完成");
                    }
                }
                //把处理完的阻塞事件移除
                iterator.remove();
            }
        }
    }
}

（四）Netty

Netty核心组件

Bootstrap和ServerBootstrap：当需要连接客户端或者服务器绑定指定端口时需要使用Bootstrap，ServerBootstrap有两种类型，一种是用于客户端的Bootstrap，一种是用于服务端的ServerBootstrap。
Channel：相当于socket，与另一端进行通信的通道，具备bind、connect、read、write等IO操作的能力。
EventLoop：事件循环，负责处理Channel的IO事件,一个EventLoopGroup包含多个EventLoop，一个EventLoop可被分配至多个Channel，一个Channel只能注册于一个EventLoop，一个EventLoop只能与一个Thread绑定。
ChannelFuture：channel IO事件的异步操作结果。
ChannelHandler：包含IO事件具体的业务逻辑。
ChannelPipeline：ChannelHandler的管道容器。

DEMO
Netty服务端

public class NettyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup parentGroup = new NioEventLoopGroup();
        EventLoopGroup childGroup = new NioEventLoopGroup();
        try {
            //2.创建服务端启动引导/辅助类：ServerBootstrap
            ServerBootstrap bootstrap = new ServerBootstrap();
            //3.给引导类配置两大线程组,确定了线程模型
            bootstrap.group(parentGroup, childGroup)
                    // (非必备)打印日志
                    .handler(new LoggingHandler(LogLevel.INFO))
                    // 4.指定 IO 模型
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new StringDecoder());
                            pipeline.addLast(new StringEncoder());
                            /**
                             *  服务端添加IdleStateHandler心跳检测处理器,添加自定义处理Handler类实现userEventTriggered()方法作为超时事件的逻辑处理.
                             *  IdleStateHandler心跳检测每十五秒进行一次读检测，如果十五秒内ChannelRead()方法未被调用则触发一次userEventTrigger()方法
                             *  服务端为读IDLE
                             *  pipeline.AddLast(new IdleStateHandler(15, 0, 0));//第一个参数为读，第二个为写，第三个为读写全部
                             */
                            pipeline.addLast(new IdleStateHandler(15, 0, 0, TimeUnit.SECONDS));
                            //5.可以自定义客户端消息的业务处理逻辑
                            pipeline.addLast(new DemoSocketServerHandler());
                        }
                    });

//            ChannelFuture future = bootstrap.bind(8888).sync().addListener(new ChannelFutureListener() {
//                @Override
//                public void operationComplete(ChannelFuture channelFuture) throws Exception {
//                    System.out.println("监听端口已经启动");
//                }
//            });
            ChannelFuture future = bootstrap.bind(8888).sync().addListener( future1 -> {
                if (future1.isSuccess()){
                    System.out.println("监听端口已经启动!");
                } else {
                    System.out.println("监听端口还未启动!");
                }
            } );
            System.out.println("服务器已启动。。。");
            future.channel().closeFuture().sync();
        } finally {
            parentGroup.shutdownGracefully();
            childGroup.shutdownGracefully();
        }
    }
}

Netty客户端

public class NettyClient {
    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new DemoSocketClientHandler());
                        }
                    });

            ChannelFuture future = bootstrap.connect("localhost", 8888).sync();
            future.channel().closeFuture().sync();
        } finally {
            if(eventLoopGroup != null) {
                eventLoopGroup.shutdownGracefully();
            }
        }
    }
}

服务端处理handler

public class DemoSocketServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        InetSocketAddress inetSocketAddress = (InetSocketAddress) ctx.channel().remoteAddress();
        String ip = inetSocketAddress.getAddress().getHostAddress();
        int port = inetSocketAddress.getPort();
        super.channelActive(ctx);
        System.out.println(ip+":"+port+" 上线了");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println(msg);
        System.out.println("Client Address ====== " + ctx.channel().remoteAddress());
        ctx.channel().writeAndFlush("from server:" + UUID.randomUUID());
        ctx.fireChannelActive();
        TimeUnit.MILLISECONDS.sleep(500);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent idleStateEvent = (IdleStateEvent) evt;
            if (idleStateEvent.state() == IdleState.READER_IDLE) {
                InetSocketAddress inetSocketAddress = (InetSocketAddress) ctx.channel().remoteAddress();
                String ip = inetSocketAddress.getAddress().getHostAddress();
                System.out.println((ip + ":" + inetSocketAddress.getPort() + "close"));
                ctx.channel().close();
            }
        }
    }
}

客户端处理handler

public class DemoSocketClientHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        System.out.println(msg);
        ctx.channel().writeAndFlush("from client: " + System.currentTimeMillis());
        TimeUnit.MILLISECONDS.sleep(5000);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.channel().writeAndFlush("from client：begin talking");
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
    //超时则关闭链路
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent idleStateEvent = (IdleStateEvent) evt;
            if (idleStateEvent.state() == IdleState.READER_IDLE) {
                InetSocketAddress inetSocketAddress = (InetSocketAddress) ctx.channel().remoteAddress();
                String ip = inetSocketAddress.getAddress().getHostAddress();
                System.out.println((ip + ":" + inetSocketAddress.getPort() + "close"));
                ctx.channel().close();
            }
        }
    }
}