Netty框架原理

用这张图表示的就是一个基本的Netty框架

通过创建两个线程池，一个负责接入， 一个负责处理

public class Start {
    public static void main(String[] args) {
            
        //初始化线程
        NioSelectorRunnablePool nioSelectorRunnablePool = new NioSelectorRunnablePool(Executors.newCachedThreadPool(), Executors.newCachedThreadPool());   //1
        
        //获取服务类
        ServerBootstrap bootstrap = new ServerBootstrap(nioSelectorRunnablePool);
        
        //绑定端口
        bootstrap.bind(new InetSocketAddress(80));
        
        System.out.println("start");
    }
}
NioSelectorRunnablePool  相当于一个线程池操作类
public class NioSelectorRunnablePool {
    
    /**
     * boss 线程数组
     */
    private final AtomicInteger bossIndex = new AtomicInteger();
    private Boss[] bosses;
    
    /**
     * worker线程数组
     */
    private final AtomicInteger workerIndex = new AtomicInteger();
    private Worker[] workers;

    public NioSelectorRunnablePool(Executor boss, Executor worker) {
        //初始化boss线程  即接入线程 
        initBoss(boss, 1);
        //根据当前核心数*2 初始化处理线程
        initWorker(worker, Runtime.getRuntime().availableProcessors() * 2);
    }

    /**
     * 初始化boss线程组
     * @param boss
     * @param count
     */
    private void initBoss(Executor boss, int count) {
        this.bosses = new NioServerBoss[count];
        for (int i = 0; i < bosses.length; i++) {
            //线程池数组
            bosses[i] = new NioServerBoss(boss, "boss thread" + (i+1), this);
        }
    }

    /**
     * 初始化worker线程
     * @param worker worker线程池
     * @param count 线程数
     */
    private void initWorker(Executor worker, int count) {
        this.workers = new NioServerWorker[count];
        for (int i = 0; i < bosses.length; i++) {
            workers[i] = new NioServerWorker(worker, "worker thread" + (i+1), this);
        }        
    }
    
    /**
     * 获取下一个boss线程
     * @return
     */
    public Boss nextBoss() {
        return bosses[Math.abs(bossIndex.getAndIncrement() % bosses.length)];
    }
    
    /**
     * 获取下一个work线程
     * @return
     */
    public Worker nextWorkr() {
        return workers[Math.abs(workerIndex.getAndIncrement() % workers.length)];
    }
}
初始化两个线程池 NioServerBoss 和NioServerWorker  两个类都实现 各自的Boss  和 Worker 接口   继承 了 AbstractNioSelector 抽象Selector
public interface Boss {
    
    /**
     * 加入一个新的ServerSocket
     * @param serverChannel
     */
    public void registerAcceptChannelTask(ServerSocketChannel serverChannel);
}
Boos
public interface Worker {
    /**
     * 加入一个新的客户端会话
     * @param channel
     */
    public void registerNewChannelTask(SocketChannel channel);

}
Worker
/**
*@Description 抽象selector线程类
*@autor:mxz
*2018-08-17
**/
public abstract class AbstractNioSelector implements Runnable{
    /**
     * 线程池
     */
    private Executor executor;
    private String threadName;
    
    /**
     * 选择器wakenUp状态标记
     */
    protected final AtomicBoolean wakenUp = new AtomicBoolean();
    
    /**
     * 线程管理对象，存储线程池数组
     */
    private NioSelectorRunnablePool selectorRunnablePool;

    protected Selector selector;

    /**
     * 任务队列
     */
    private final Queue<Runnable> taskQueue = new ConcurrentLinkedQueue<Runnable>();
    

    public AbstractNioSelector(Executor executor, String threadName, NioSelectorRunnablePool selectorRunnablePool) {
        this.executor = executor;
        this.threadName = threadName;
        this.selectorRunnablePool = selectorRunnablePool;
        //一个线程 加入一个selector
        openSelector();
    }
    
    /**
     * 获取线程管理对象
     * @return
     */
    protected NioSelectorRunnablePool  getselectorRunnablePool() {
        return this.selectorRunnablePool;
    }
    /**
     * 获取selector并启动线程
     */
    private void openSelector() {
        try {
            this.selector = Selector.open();
        } catch (IOException e) {
            throw new RuntimeException("Failed to create a selector");
        }
        //线程池执行该线程
        executor.execute(this);
    }

    @Override
    public void run() {
        Thread.currentThread().setName(this.threadName);
        
        while (true) {
            try {
                wakenUp.set(false);
                //当注册事件到达时，方法返回，否则该方法会一直阻塞
                select(selector);
                
                //运行任务队列中的任务
                processTaskQueue();
                
                process(selector);
            } catch (Exception e) {
                
            }
        }
    }
    /**
     * 注册一个任务并激活selector 重新执行
     * @param task
     */
    protected final void registerTask(Runnable task) {
        taskQueue.add(task);
        
        Selector selector = this.selector;
        
        if (selector != null) {
            if (wakenUp.compareAndSet(false, true)) {
                //会首先唤醒Boss  接入总线线程  唤醒阻塞在selector上的线程， 去做其他事情，例如注册channel改变interestOps的值
                selector.wakeup();
            }
        } else {
            taskQueue.remove(task);
        }
    }
    
    /**
     *  
     */
    
    //执行队列中的任务
    private void processTaskQueue() {
        for(;;) {
            final Runnable task = taskQueue.poll();
            if (task == null) {
                break;
            }
            task.run();
        }
    }

    /**
     * selector抽象方法
     * @param selector
     * @return
     * @throws IOException
     */
    protected abstract int select(Selector selector) throws IOException;

    /**
     * selector的业务处理
     * @param selector
     * @return
     * @throws IOException
     */
    protected abstract void process(Selector selector) throws IOException;
}

执行openSelector() 创建 selector  execute 执行线程  执行各自的 select（）

public class NioServerBoss extends AbstractNioSelector implements Boss {

    public NioServerBoss(Executor boss, String threadName, NioSelectorRunnablePool selectorRunnablePool) {
        super(boss, threadName, selectorRunnablePool);
    }

    @Override
    protected int select(Selector selector) throws IOException {
        return selector.select();
    }

    @Override
    protected void process(Selector selector) throws IOException {
        Set<SelectionKey> selectedKeys = selector.selectedKeys();
        if (selectedKeys.isEmpty()) {
            return;
        }
        
        for (SelectionKey key : selectedKeys) {
            selectedKeys.remove(key);
            ServerSocketChannel server = (ServerSocketChannel) key.channel();
            //新客户端
            SocketChannel channel = server.accept();
            //设置为非阻塞
            channel.configureBlocking(false);
            //获取一个worker
            Worker nextworker = getselectorRunnablePool().nextWorkr();
            //注册新客户端介入任务给另一个线程任务队列加入新任务
            nextworker.registerNewChannelTask(channel);
            System.out.println("新客户连接");
        }
    }

    @Override
    public void registerAcceptChannelTask(final ServerSocketChannel serverChannel) {
        final Selector selector = this.selector;
        registerTask(new Runnable() {
            @Override
            public void run() {
                try {
                    serverChannel.register(selector, SelectionKey.OP_ACCEPT);
                } catch (ClosedChannelException e) {
                    e.printStackTrace();
                }
            }
        });
    }

}
public class NioServerWorker extends AbstractNioSelector implements Worker{

    public NioServerWorker(Executor worker, String threadName, NioSelectorRunnablePool selectorRunnablePool) {
        super(worker, threadName, selectorRunnablePool);
    }

    @Override
    protected int select(Selector selector) throws IOException {
        return selector.select();
    }

    @Override
    protected void process(Selector selector) throws IOException {
        Set<SelectionKey> selectedKeys = selector.selectedKeys();
        if (selectedKeys.isEmpty()) {
            return;
        }
        Iterator<SelectionKey> iterator = this.selector.selectedKeys().iterator();
        while (iterator.hasNext()) {
            SelectionKey key = iterator.next();
            //移除 防止重复提交
            iterator.remove();
            
            //得到事件发生的socket通道
            SocketChannel channel = (SocketChannel) key.channel();

            //数据总长度
            int ret = 0;
            boolean failure = true;
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            //读取数据
            try {
                ret = channel.read(buffer);
                failure = false;
            } catch (Exception e) {
            }
            //判断是否连接已断开
            if (ret <= 0 || failure) {
                key.channel();
                System.out.println("客户端已断开连接");
            } else {
                System.out.println("收到数据：" + new String (buffer.array()));
                
                //回 写数据
                ByteBuffer outBuf = ByteBuffer.wrap("收到
".getBytes());
                channel.write(outBuf);// 将消息发送到客户端
            }
        }
    }

此时都会selector.selector() 阻塞等待连接

此时再看 bootstrap.bind(new InetSocketAddress(80));  会调用 

public class ServerBootstrap {

    private NioSelectorRunnablePool selectorRunnablePool;

    public ServerBootstrap(NioSelectorRunnablePool selectorRunnablePool) {
        this.selectorRunnablePool = selectorRunnablePool;
    }

    public void bind(final InetSocketAddress localAddress) {
        try {
            //获得一个ServerSocket通道
            ServerSocketChannel serverChannel = ServerSocketChannel.open();
            //设置通道为非阻塞
            serverChannel.configureBlocking(false);
            //将该通道对应的serverSocket绑定到port
            serverChannel.socket().bind(localAddress);
            
            //获取一个boss线程
            Boss nextBoss = selectorRunnablePool.nextBoss();
            //向当前boss 线 程注册一个ServerSocket通道
            nextBoss.registerAcceptChannelTask(serverChannel);
        } catch (Exception e) {
            // TODO: handle exception
        }
    }

}

这个时候通过获取下一个线程注入任务池（其实就一个） 这里可以看AbstractSelector 中的nextBoss 和nextWorker 方法 从线程数组循环拿出线程

这个时候会将当前通道在selector上注册 OP_ACCEPT  的事件 并将这个任务添加到Taskqueue

/**
     * 注册一个任务并激活selector 重新执行
     * @param task
     */
    protected final void registerTask(Runnable task) {
        taskQueue.add(task);
        
        Selector selector = this.selector;
        
        if (selector != null) {
            if (wakenUp.compareAndSet(false, true)) {
                //会首先唤醒Boss  接入总线线程  唤醒阻塞在selector上的线程， 去做其他事情，例如注册channel改变interestOps的值
                selector.wakeup();
            }
        } else {
            taskQueue.remove(task);
        }
    }

这个时候会唤醒selector  不过唤醒的是boss的selector

唤醒后之前的阻塞会继续往下执行

　　　　　　　　　　wakenUp.set(false);
                //当注册事件到达时，方法返回，否则该方法会一直阻塞
                select(selector);
                
                //运行任务队列中的任务
                processTaskQueue();
                
                process(selector);

先执行任务  也就是 channel regiter 到 selector 上

执行 Boss中的 process 的方法

    @Override
    protected void process(Selector selector) throws IOException {
        Set<SelectionKey> selectedKeys = selector.selectedKeys();
        if (selectedKeys.isEmpty()) {
            return;
        }
        
        for (SelectionKey key : selectedKeys) {
            selectedKeys.remove(key);
            ServerSocketChannel server = (ServerSocketChannel) key.channel();
            //新客户端
            SocketChannel channel = server.accept();
            //设置为非阻塞
            channel.configureBlocking(false);
            //获取一个worker
            Worker nextworker = getselectorRunnablePool().nextWorkr();
            //注册新客户端介入任务给另一个线程任务队列加入新任务
            nextworker.registerNewChannelTask(channel);
            System.out.println("新客户连接");
        }
    }

同理再去 走相同的路线 把获取到的通道绑到 worker的selector上


 
 
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原文地址：https://www.cnblogs.com/mxz1994/p/9512832.html