NIO TimeServer

整个TimeServer的代码较多，不过逻辑应该是比较清楚的，还加了注释。

public class NIOTimeServer {
    //默认端口号
    private static final int PORT = 8585;
    public static void main(String[] args) throws IOException {
        new Thread(new TimeServerTask(PORT)).start();
    }
    private static class TimeServerTask implements Runnable{
        private Selector selector;
        private ServerSocketChannel serverSocketChannel;
        //停止channel 标识
        private volatile boolean stop = false;
        /**
        * 初始化channel 监听端口 初始化selector
        */
        public TimeServerTask(int port) {
            try {
                //初始化通道和选择器
                selector = Selector.open();
                serverSocketChannel = ServerSocketChannel.open();
                //设置为非阻塞模式
                serverSocketChannel.configureBlocking(false);
                //绑定端口
                serverSocketChannel.bind(new InetSocketAddress(port));
                //将通道注册到选择器
                serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
                System.out.println("The TimeServer started at port: " + port);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        /**
        * 停止
        */
        public void stop(){
            this.stop = true;
        }
        @Override
        public void run() {
            while(!stop){
                try{
                    //这里使用带有时间限制的阻塞select方法
                    selector.select(1000);
                    //获取就绪通道
                    Set<SelectionKey> selectionKeys = selector.selectedKeys();
                    //遍历就绪通道
                    Iterator<SelectionKey> iterator = selectionKeys.iterator();
                    SelectionKey selectionKey;
                    while(iterator.hasNext()){
                        selectionKey = iterator.next();
                        iterator.remove();
                        try{
                            handleInput(selectionKey);
                        }catch (IOException e){
                            selectionKey.cancel();
                            if(null != selectionKey.channel()){
                                selectionKey.channel().close();
                            }
                        }
                    }
                }catch (Throwable t){
                    t.printStackTrace();
                }
            }
            //停止 就关闭selector selector关闭后 所有注册到它上面的channel也会被关闭
            if(null != selector){
                try {
                    selector.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

/**
        * 处理输入
        */
        private void handleInput(SelectionKey selectionKey) throws IOException {
            //先使用isValid方法判断是否可用
            if(selectionKey.isValid()){
                //判断是否可接收连接
                if(selectionKey.isAcceptable()){
                    //从SelectionKey中拿到与之对应的ServerChannel
                    ServerSocketChannel channel = (ServerSocketChannel) selectionKey.channel();
                    //建立连接
                    SocketChannel socketChannel = channel.accept();
                    //非阻塞模式
                    socketChannel.configureBlocking(false);
                    //将socketChannel也注册到selector
                    socketChannel.register(selector,SelectionKey.OP_READ);
                }
                if(selectionKey.isReadable()){
                    //读取数据
                    SocketChannel channel = (SocketChannel) selectionKey.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(1025-1);
                    //因为channel是非阻塞的 所以read方法可能返回-1 0 以及正常读取到的字节数量
                    int read = channel.read(buffer);
                    if(read>0){
                        //回绕缓冲区 便于获取有效元素
                        buffer.flip();
                        byte[] elements = new byte[buffer.remaining()];
                        //将buffer中的数据写入数组
                        buffer.get(elements);
                        String content = new String(elements, StandardCharsets.UTF_8);
                        System.out.println("The TimeServer received order: " + content );
                        String response = "QUERY TIME ORDER ".equalsIgnoreCase(content)?new Date(System.currentTimeMillis()).toString():"BAD ORDER";
                        //写回响应
                        doWrite(response,channel);
                    }else if(read<0){
                        //对端链路关闭
                        selectionKey.cancel();
                        channel.close();
                    }else {
                        //读到0字节 忽略
                    }
                }
            }
        }
        private void doWrite(String response,SocketChannel socketChannel) throws IOException {
            if(response!=null && response.trim().length()>0){
                socketChannel.write(ByteBuffer.wrap(response.getBytes(StandardCharsets.UTF_8)));
            }
        }
    }
}

这样我们启动main线程，就会启动这个TimeServer。