Netty 之旅二：口口相传的高性能 Netty 到底是什么？

/**
 * @Description netty简易聊天室
 *
 * @Author 一枝花算不算浪漫
 * @Date 2020/8/10 6:52 上午
 */
public final class NettyChatServer {
    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));
    public static void main(String[] args) throws Exception {
        // 1. EventLoopGroup
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            // 2. 服务端引导器
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            // 3. 设置线bootStrap信息
            serverBootstrap.group(bossGroup, workerGroup)
                    // 4. 设置ServerSocketChannel的类型
                    .channel(NioServerSocketChannel.class)
                    // 5. 设置参数
                    .option(ChannelOption.SO_BACKLOG, 100)
                    // 6. 设置ServerSocketChannel对应的Handler，只能设置一个
                    .handler(new LoggingHandler(LogLevel.INFO))
                    // 7. 设置SocketChannel对应的Handler
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            // 可以添加多个子Handler
                            p.addLast(new LoggingHandler(LogLevel.INFO));
                            p.addLast(new ChatNettyHandler());
                        }
                    });
            // 8. 绑定端口
            ChannelFuture f = serverBootstrap.bind(PORT).sync();
            // 9. 等待服务端监听端口关闭，这里会阻塞主线程
            f.channel().closeFuture().sync();
        } finally {
            // 10. 优雅地关闭两个线程池
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    private static class ChatNettyHandler extends SimpleChannelInboundHandler<ByteBuf> {
        @Override
        public void channelActive(ChannelHandlerContext ctx) {
            System.out.println("one conn active: " + ctx.channel());
            // channel是在ServerBootstrapAcceptor中放到EventLoopGroup中的
            ChatHolder.join((SocketChannel) ctx.channel());
        }
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, ByteBuf byteBuf) throws Exception {
            byte[] bytes = new byte[byteBuf.readableBytes()];
            byteBuf.readBytes(bytes);
            String content = new String(bytes, StandardCharsets.UTF_8);
            System.out.println(content);
            if (content.equals("quit\r\n")) {
                ctx.channel().close();
            } else {
                ChatHolder.propagate((SocketChannel) ctx.channel(), content);
            }
        }
        @Override
        public void channelInactive(ChannelHandlerContext ctx) {
            System.out.println("one conn inactive: " + ctx.channel());
            ChatHolder.quit((SocketChannel) ctx.channel());
        }
    }
    private static class ChatHolder {
        static final Map<SocketChannel, String> USER_MAP = new ConcurrentHashMap<>();
        /**
         * 加入群聊
         */
        static void join(SocketChannel socketChannel) {
            // 有人加入就给他分配一个id
            String userId = "用户"+ ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);
            send(socketChannel, "您的id为：" + userId + "\n\r");
            for (SocketChannel channel : USER_MAP.keySet()) {
                send(channel, userId + " 加入了群聊" + "\n\r");
            }
            // 将当前用户加入到map中
            USER_MAP.put(socketChannel, userId);
        }
        /**
         * 退出群聊
         */
        static void quit(SocketChannel socketChannel) {
            String userId = USER_MAP.get(socketChannel);
            send(socketChannel, "您退出了群聊" + "\n\r");
            USER_MAP.remove(socketChannel);
            for (SocketChannel channel : USER_MAP.keySet()) {
                if (channel != socketChannel) {
                    send(channel, userId + " 退出了群聊" + "\n\r");
                }
            }
        }
        /**
         * 扩散说话的内容
         */
        public static void propagate(SocketChannel socketChannel, String content) {
            String userId = USER_MAP.get(socketChannel);
            for (SocketChannel channel : USER_MAP.keySet()) {
                if (channel != socketChannel) {
                    send(channel, userId + ": " + content);
                }
            }
        }
        /**
         * 发送消息
         */
        static void send(SocketChannel socketChannel, String msg) {
            try {
                ByteBufAllocator allocator = ByteBufAllocator.DEFAULT;
                ByteBuf writeBuffer = allocator.buffer(msg.getBytes().length);
                writeBuffer.writeCharSequence(msg, Charset.defaultCharset());
                socketChannel.writeAndFlush(writeBuffer);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)      
        .channel(NioServerSocketChannel.class)
        .option(ChannelOption.SO_BACKLOG, 100)
        .handler(new LoggingHandler(LogLevel.INFO))
        .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            public void initChannel(SocketChannel ch) throws Exception {
                ChannelPipeline p = ch.pipeline();
                p.addLast(new LoggingHandler(LogLevel.INFO));
                p.addLast(new ChatNettyHandler());
            }
        });

ByteBufAllocator allocator = ByteBufAllocator.DEFAULT;
ByteBuf buffer = allocator.buffer(length);

@Sharable
public class DiscardHandler extends ChannelInboundHandlerAdapter {
	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) {
		ReferenceCountUtil.release(msg);
	}
}

public class SimpleDiscardHandler
	extends SimpleChannelInboundHandler<Object> {
	@Override
	public void channelRead0(ChannelHandlerContext ctx,
									Object msg) {
			// 不用调用ReferenceCountUtil.release(msg)也会释放资源
	}
}

public class SslHandler extends ByteToMessageDecoder implements ChannelOutboundHandler

ChannelPipeline pipeline = ..;
FirstHandler firstHandler = new FirstHandler();
// 先添加一个Handler到ChannelPipeline中
pipeline.addLast("handler1", firstHandler);
// 这个Handler放在了first,意味着放在了handler1之前
pipeline.addFirst("handler2", new SecondHandler());
// 这个Handler被放到了last,意味着在handler1之后
pipeline.addLast("handler3", new ThirdHandler());
...
// 通过名称删除
pipeline.remove("handler3");
// 通过对象删除
pipeline.remove(firstHandler);
// 名称"handler2"替换成名称"handler4",并切handler2的实例替换成了handler4的实例
pipeline.replace("handler2", "handler4", new ForthHandler());

ChannelHandlerContext ctx = ..;
// 获取channel引用
Channel channel = ctx.channel();
// 通过channel写入缓冲区
channel.write(Unpooled.copiedBuffer("Netty in Action",
CharsetUtil.UTF_8));

ChannelHandlerContext ctx = ..;
// 获取ChannelHandlerContext
ChannelPipeline pipeline = ctx.pipeline();
// 通过ChannelPipeline写入缓冲区
pipeline.write(Unpooled.copiedBuffer("Netty in Action",
CharsetUtil.UTF_8));

ChannelHandlerContext ctx = ..;
// 直接通过ChannelHandlerContext写数据,发送到下一个handler
ctx.write(Unpooled.copiedBuffer("Netty in Action", CharsetUtil.UTF_8));

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.CharsetUtil;
import java.util.concurrent.atomic.AtomicInteger;
/**
 * @Author: wuxiaofei
 * @Date: 2020/8/15 0015 19:15
 * @Version: 1.0
 * @Description:入站处理器
 */
@ChannelHandler.Sharable
public class DelimiterServerHandler extends ChannelInboundHandlerAdapter {
    private AtomicInteger counter = new AtomicInteger(0);
    private AtomicInteger completeCounter = new AtomicInteger(0);
    /*** 服务端读取到网络数据后的处理*/
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in = (ByteBuf)msg;
        String request = in.toString(CharsetUtil.UTF_8);
        System.out.println("Server Accept["+request
                +"] and the counter is:"+counter.incrementAndGet());
        String resp = "Hello,"+request+". Welcome to Netty World!"
                + DelimiterEchoServer.DELIMITER_SYMBOL;
        ctx.writeAndFlush(Unpooled.copiedBuffer(resp.getBytes()));
    }
    /*** 服务端读取完成网络数据后的处理*/
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx)
            throws Exception {
        ctx.fireChannelReadComplete();
        System.out.println("the ReadComplete count is "
                +completeCounter.incrementAndGet());
    }
    /*** 发生异常后的处理*/
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import java.net.InetSocketAddress;
/**
 * @Author: wuxiaofei
 * @Date: 2020/8/15 0015 19:17
 * @Version: 1.0
 * @Description:服务端
 */
public class DelimiterEchoServer {
    public static final String DELIMITER_SYMBOL = "@~";
    public static final int PORT = 9997;
    public static void main(String[] args) throws InterruptedException {
        DelimiterEchoServer delimiterEchoServer = new DelimiterEchoServer();
        System.out.println("服务器即将启动");
        delimiterEchoServer.start();
    }
    public void start() throws InterruptedException {
        final DelimiterServerHandler serverHandler = new DelimiterServerHandler();
        EventLoopGroup group = new NioEventLoopGroup();/*线程组*/
        try {
            ServerBootstrap b = new ServerBootstrap();/*服务端启动必须*/
            b.group(group)/*将线程组传入*/
                .channel(NioServerSocketChannel.class)/*指定使用NIO进行网络传输*/
                .localAddress(new InetSocketAddress(PORT))/*指定服务器监听端口*/
                /*服务端每接收到一个连接请求，就会新启一个socket通信，也就是channel，
                所以下面这段代码的作用就是为这个子channel增加handle*/
                .childHandler(new ChannelInitializerImp());
            ChannelFuture f = b.bind().sync();/*异步绑定到服务器，sync()会阻塞直到完成*/
            System.out.println("服务器启动完成，等待客户端的连接和数据.....");
            f.channel().closeFuture().sync();/*阻塞直到服务器的channel关闭*/
        } finally {
            group.shutdownGracefully().sync();/*优雅关闭线程组*/
        }
    }
    private static class ChannelInitializerImp extends ChannelInitializer<Channel> {
        @Override
        protected void initChannel(Channel ch) throws Exception {
            ByteBuf delimiter = Unpooled.copiedBuffer(DELIMITER_SYMBOL
                    .getBytes());
            //服务端收到数据包后经过DelimiterBasedFrameDecoder即分隔符基础框架解码器解码为一个个带有分隔符的数据包。
            ch.pipeline().addLast( new DelimiterBasedFrameDecoder(1024,
                    delimiter));
            ch.pipeline().addLast(new DelimiterServerHandler());
        }
    }
}

EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();

ServerBootstrap serverBootstrap = new ServerBootstrap();

serverBootstrap.group(bossGroup, workerGroup);

serverBootstrap.channel(NioServerSocketChannel.class);

serverBootstrap.option(ChannelOption.SO_BACKLOG, 100);

serverBootstrap.handler(new LoggingHandler(LogLevel.INFO));

serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
    @Override
    public void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline p = ch.pipeline();
        p.addLast(new LoggingHandler(LogLevel.INFO));
        p.addLast(new ChatNettyHandler());
    }
});