Selector selector = Selector.open();

channel.configureBlocking(false);SelectionKey?key?=?channel.register(selector,?SelectionKey.OP_READ);

int interestSet = SelectionKey.OP_READ | SelectionKey.OP_WRITE;

channel.register(selector, SelectionKey.OP_READ);channel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);

int interestSet = selectionKey.interestOps();
boolean isInterestedInAccept = interestSet & SelectionKey.OP_ACCEPT;boolean isInterestedInConnect = interestSet & SelectionKey.OP_CONNECT;boolean isInterestedInRead = interestSet & SelectionKey.OP_READ;boolean isInterestedInWrite = interestSet & SelectionKey.OP_WRITE;

int?readySet?=?selectionKey.readyOps();selectionKey.isAcceptable();selectionKey.isConnectable();selectionKey.isReadable();selectionKey.isWritable();

Channel channel = selectionKey.channel();Selector selector = selectionKey.selector();

selectionKey.attach(theObject);Object attachedObj = selectionKey.attachment();

SelectionKey key = channel.register(selector, SelectionKey.OP_READ, theObject);

Set selectedKeys = selector.selectedKeys();
Iterator keyIterator = selectedKeys.iterator();
while(keyIterator.hasNext()) {
 SelectionKey key = keyIterator.next();
 if(key.isAcceptable()) { // a connection was accepted by a ServerSocketChannel.
 } else if (key.isConnectable()) { // a connection was established with a remote server.
 } else if (key.isReadable()) { // a channel is ready for reading
 } else if (key.isWritable()) { // a channel is ready for writing }
 keyIterator.remove();}

public class NioEchoServer { private static final int BUF_SIZE = 256; private static final int TIMEOUT = 3000;
 public static void main(String args[]) throws Exception { // 打開服務(wù)端 Socket ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
 // 打開 Selector Selector selector = Selector.open();
 // 服務(wù)端 Socket 監(jiān)聽8080端口, 并配置為非阻塞模式 serverSocketChannel.socket().bind(new InetSocketAddress(8080)); serverSocketChannel.configureBlocking(false);
 // 將 channel 注冊到 selector 中. // 通常我們都是先注冊一個(gè) OP_ACCEPT 事件, 然后在 OP_ACCEPT 到來時(shí), 再將這個(gè) Channel 的 OP_READ // 注冊到 Selector 中. serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
 while (true) { // 通過調(diào)用 select 方法, 阻塞地等待 channel I/O 可操作 if (selector.select(TIMEOUT) == 0) { System.out.print("."); continue; }
 // 獲取 I/O 操作就緒的 SelectionKey, 通過 SelectionKey 可以知道哪些 Channel 的哪類 I/O 操作已經(jīng)就緒. Iterator keyIterator = selector.selectedKeys().iterator();
 while (keyIterator.hasNext()) {
 SelectionKey key = keyIterator.next();
 // 當(dāng)獲取一個(gè) SelectionKey 后, 就要將它刪除, 表示我們已經(jīng)對這個(gè) IO 事件進(jìn)行了處理. keyIterator.remove();
 if (key.isAcceptable()) { // 當(dāng) OP_ACCEPT 事件到來時(shí), 我們就有從 ServerSocketChannel 中獲取一個(gè) SocketChannel, // 代表客戶端的連接 // 注意, 在 OP_ACCEPT 事件中, 從 key.channel() 返回的 Channel 是 ServerSocketChannel. // 而在 OP_WRITE 和 OP_READ 中, 從 key.channel() 返回的是 SocketChannel. SocketChannel clientChannel = ((ServerSocketChannel) key.channel()).accept(); clientChannel.configureBlocking(false); //在 OP_ACCEPT 到來時(shí), 再將這個(gè) Channel 的 OP_READ 注冊到 Selector 中. // 注意, 這里我們?nèi)绻麤]有設(shè)置 OP_READ 的話, 即 interest set 仍然是 OP_CONNECT 的話, 那么 select 方法會(huì)一直直接返回. clientChannel.register(key.selector(), OP_READ, ByteBuffer.allocate(BUF_SIZE)); }
 if (key.isReadable()) { SocketChannel clientChannel = (SocketChannel) key.channel(); ByteBuffer buf = (ByteBuffer) key.attachment(); long bytesRead = clientChannel.read(buf); if (bytesRead == -1) { clientChannel.close(); } else if (bytesRead > 0) { key.interestOps(OP_READ | SelectionKey.OP_WRITE); System.out.println("Get data length: " + bytesRead); } }
 if (key.isValid() && key.isWritable()) { ByteBuffer buf = (ByteBuffer) key.attachment(); buf.flip(); SocketChannel clientChannel = (SocketChannel) key.channel();
 clientChannel.write(buf);
 if (!buf.hasRemaining()) { key.interestOps(OP_READ); } buf.compact(); } } } }}