Java 非阻塞io(NIO)

執行流程

1.Server

1. 開啟通道選擇器Selector

2. 建立ServerSocketChannel通道 並繫結介面

3. ServerSocketChannel 通道註冊到selector serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT)並指定SelectionKey（通道型別）

4. 呼叫selector.select()方法檢查IO就緒事件

5. 如果就緒 1.）serverSocketChannel.accept()開始處理

2.Client

6. SocketChannel.open()開啟channel
7. bind繫結IP和埠
8. 開始讀寫

程式碼展示

Server

SelectionKey.OP_READ 對應 00000001，通道中有資料可以進行讀取 SelectionKey.OP_WRITE 對應 00000100，可以往通道中寫入資料 SelectionKey.OP_CONNECT 對應 00001000，成功建立 TCP 連線 SelectionKey.OP_ACCEPT 對應 00010000，接受 TCP 連線

//            建立通道選擇器。
            Selector selector = Selector.open();
//            建立通道
            ServerSocketChannel serverSocketChannel =
 
 ServerSocketChannel.open();
            serverSocketChannel.socket().bind(new InetSocketAddress(8081));
//            將通道註冊到selector上
//            如果為 true，則此通道將被置於阻塞模式；如果為 false，則此通道將被置於非阻塞模式
            serverSocketChannel.configureBlocking(false);
//            可以使用陣列組合
            serverSocketChannel.
 
register(selector, SelectionKey.OP_ACCEPT);
            while (true) {
//              獲取通道數目
                int readyChannels = selector.select();
                if(readyChannels == 0){
                    continue;
                }
//                獲取SelectionKey既對通道的操作
                Set<SelectionKey>  readyKey = selector.selectedKeys();
//                遍歷
                Iterator<SelectionKey> iterator = readyKey.iterator();
                while(iterator.hasNext()){
                    SelectionKey key = iterator.next();
                    iterator.remove();
//                    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
//                    }

                    if (key.isAcceptable()) {
                        // 有已經接受的新的到服務端的連線
                        SocketChannel socketChannel = serverSocketChannel.accept();
                        // 有新的連線並不代表這個通道就有資料，
                        // 這裡將這個新的 SocketChannel 註冊到 Selector，監聽 OP_READ 事件，等待資料
                        socketChannel.configureBlocking(false);
                        socketChannel.register(selector, SelectionKey.OP_READ);
                    } else if (key.isReadable()) {
                        // 有資料可讀
                        // 上面一個 if 分支中註冊了監聽 OP_READ 事件的 SocketChannel
                        SocketChannel socketChannel = (SocketChannel) key.channel();
//                        建立快取空間
                        ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                        int num = socketChannel.read(readBuffer);
                        if (num > 0) {
                            // 處理進來的資料...
                            System.out.println("收到資料：" + new String(readBuffer.array()).trim());
                            ByteBuffer buffer = ByteBuffer.wrap("返回給客戶端的資料...".getBytes());
                            socketChannel.write(buffer);
                        } else if (num == -1) {
                            // -1 代表連線已經關閉
                            socketChannel.close();
                        }
                    }
                }
            }
        }catch(IOException e){
//            key.cancel();
//            channel.socket().close();
//            channel.close();
            return;
        }

    }
}

client

public class Client {

    public static void main(String[] args) {
        try {
            SocketChannel socketChannel = SocketChannel.open();
            socketChannel.connect(new InetSocketAddress("localhost",8081));
//            傳送請求
            ByteBuffer buffer = ByteBuffer.wrap("你好嗎".getBytes());
            socketChannel.write(buffer);
//            獲取server響應
            ByteBuffer readBuffer = ByteBuffer.allocate(1024);
            int num ;
            if((num = socketChannel.read(readBuffer))> 0 ){
                readBuffer.flip();
                byte[] result = new byte[num];
                readBuffer.get(result);
                String  demo = new String(result,"UTF-8");
                System.out.println("返回值："+demo);
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

結果和分析

server client