NIO核心概念和demo

参考 ：https://wiki.jikexueyuan.com/project/java-nio-zh/java-nio-tutorial.html

SocketChannel

　　建立一个SocketChannel连接　　open()

　　关闭一个SocketChannel连接　　close()

　　从SocketChannel中读数据　　　read()

　　向SocketChannel写数据　　　　write()

　　非阻塞模式

　　connect()

ServerSocketChannel　

扫描二维码关注公众号，回复： 11077676 查看本文章

　　打开ServerSocketChannel  open

　　关闭ServerSocketChannel  close

　　监听链接　　　　accept

　　非阻塞模式　　　serverSocketChannel.configureBlocking(false)

Selector

　　

SelectorKey

1. SelectionKey.OP_CONNECT
2. SelectionKey.OP_ACCEPT
3. SelectionKey.OP_READ
4. SelectionKey.OP_WRITE

Buffer 

　　

　　ByteBuffer   CharBuffer   DoubleBuffer  FloatBuffer  IntBuffer  LongBuffer  ShortBuffer

RandomAccessFile aFile = new RandomAccessFile("data/nio-data.txt", "rw");
    FileChannel inChannel = aFile.getChannel();

    ByteBuffer buf = ByteBuffer.allocate(48);

    int bytesRead = inChannel.read(buf);
    while (bytesRead != -1) {

      System.out.println("Read " + bytesRead);
      buf.flip();

      while(buf.hasRemaining()){
          System.out.print((char) buf.get());
      }

      buf.clear();
      bytesRead = inChannel.read(buf);
    }
    aFile.close();

利用Buffer读写数据，通常遵循四个步骤：

• 把数据写入buffer；
• 调用flip； 把buffer从写模式调整为读模式
• 从Buffer中读取数据；
• 调用buffer.clear()或者buffer.compact()  ；清空buffer

一个Buffer有三个属性是必须掌握的，分别是：

• capacity容量
• position位置
• limit限制

　　

Channel

• FileChannel
• DatagramChannel
• SocketChannel
• ServerSocketChannel

public class IoServer {
    private int port =8080;

    private Selector selector;
    private ByteBuffer buffer  = ByteBuffer.allocate(1024);

    public IoServer(int port){
        try {
            this.port = port;
            ServerSocketChannel server = ServerSocketChannel.open();
            server.bind(new InetSocketAddress(this.port));
            //兼容BIO
            server.configureBlocking(false);//设置之后为非阻塞

            selector = Selector.open();
            server.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void listen(){
        System.out.println("listen on " + this.port);
        while (true){
            try {
                selector.select();
                Set<SelectionKey> keys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = keys.iterator();
                while (iterator.hasNext()){
                    SelectionKey key = iterator.next();
                    iterator.remove();
                    process(key);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void process(SelectionKey key) throws IOException {
        if(key.isAcceptable()){
            ServerSocketChannel server = (ServerSocketChannel) key.channel();
            //非阻塞
            SocketChannel channel = server.accept();
            channel.configureBlocking(false);
            key = channel.register(selector, SelectionKey.OP_READ);
        }else if(key.isReadable()){
            //
        }else if (key.isWritable()){
            //
        }

    }

    public static void main(String[] args) {
        new IoServer(8080).listen();
    }