如何通過NIO實現(xiàn)群聊？【黑馬程序員】

1.NIO群聊實現(xiàn)步驟

·構(gòu)建Selector以及服務(wù)端監(jiān)聽通

·道啟動監(jiān)聽并處理建立連接請求

·處理讀數(shù)據(jù)

·群發(fā)數(shù)據(jù)實現(xiàn)

·客戶端測試實現(xiàn)

2. 服務(wù)端實現(xiàn)
2.0 服務(wù)端完整代碼服務(wù)端的主要功能如下

(1)開放監(jiān)聽端口，方法ChatServer構(gòu)造方法

(2)處理鏈接請求，方法listener實現(xiàn)連接的建立

(2)讀取消息內(nèi)容，方法readData

(4)轉(zhuǎn)發(fā)消息給當前所有在線的人，方法sendData2All

package com.hgy.chat;
/**
* 群聊服務(wù)器
*/
public class ChatServer {
    private ServerSocketChannel serverSocketChannel;
    private Selector selector;
    /**
    * 初始化服務(wù)端
    */
    public ChatServer() {
        try {
            // 創(chuàng)建Selector以及ServerSocketChannel
            selector = Selector.open();
            serverSocketChannel = serverSocketChannel.open();
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.socket().bind(new InetSocketAddress(8888));
            //將服務(wù)端監(jiān)聽通道注冊到Selector中
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (Exception e) {
            e.printStackTrace();
        }   
    }
    /**
    * 監(jiān)聽客戶端操作
    */
    public void listener() {
        while (true) {
            try {
                if (selector.select(1000) == 0) {
                continue;
            }
            //獲得所有有事件的key
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
                while (iterator.hasNext()) {
                    SelectionKey key = iterator.next();
                    //如果當前key是處理鏈接類型
                    if (key.isAcceptable()) {
                        SocketChannel socketChannel =
                        serverSocketChannel.accept();
                        socketChannel.configureBlocking(false);
                        socketChannel.register(selector, SelectionKey.OP_READ);
                    }
                    // 當前鏈接是讀數(shù)據(jù)類型
                    if (key.isReadable()) {
                        readData(key);
                    }
                    iterator.remove();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    /**
    * 讀取數(shù)據(jù)并群發(fā)給所有的用戶
    * @param key
    */
    private void readData(SelectionKey key) {
        try {
            if (key.isReadable()) {
                SocketChannel channel = (SocketChannel) key.channel();
                ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
                channel.read(byteBuffer);
                String s = new String(byteBuffer.array());
                // 寫到其他所有客戶端
                sendData2All(s);
        }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /**
    * 群發(fā)給所有的用戶
    * @param msg 需要發(fā)送的消息
    */
    private void sendData2All(String msg) {
        try {
            // 當前在selector上注冊的所有key就是所有用戶
            Set<SelectionKey> keys = selector.keys();
            for (SelectionKey key : keys) {
                // 獲取每個用戶的通道
                SelectableChannel channel = key.channel();
                // 實現(xiàn)數(shù)據(jù)發(fā)送
                if (channel instanceof SocketChannel) {
                    System.out.println(":::" + msg);
                    ByteBuffer byteBuffer = ByteBuffer.wrap(msg.getBytes());
                    SocketChannel socketChannel = (SocketChannel) channel;
                    socketChannel.write(byteBuffer);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        ChatServer chatServer = new ChatServer();
        chatServer.listener();
    }
}

2.1 構(gòu)建Selector以及服務(wù)端監(jiān)聽通道

當ChatServer對象被創(chuàng)建時具體實現(xiàn)步驟如下

（1）創(chuàng)建serverSocketChannel對象

（2）設(shè)置處理模式為非阻塞模式

（3）綁定監(jiān)聽端口

（4）將channel注冊到selector中

public class ChatServer {
    private ServerSocketChannel serverSocketChannel;
    private Selector selector;
    /**
    * 初始化服務(wù)端
    */
    public ChatServer() {
        try {
            // 創(chuàng)建Selector以及ServerSocketChannel
            selector = Selector.open();
            serverSocketChannel = serverSocketChannel.open();
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.socket().bind(new InetSocketAddress(8888));
            //將服務(wù)端監(jiān)聽通道注冊到Selector中
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2.2 實現(xiàn)監(jiān)聽并處理建立連接請求

連接請求處理實現(xiàn)步驟

（1）獲得所有有事件的key，通過key就可以拿到用戶的SocketChannel

（2）循環(huán)遍歷每一個key，判斷當前是讀事件，還是建立連接事件

（3）如果是建立連接事件則直接將該通道注冊到selector中

（4）如果是讀數(shù)據(jù)事件就交給具體的讀數(shù)據(jù)方法處理數(shù)據(jù)

2.3 處理讀數(shù)據(jù)數(shù)據(jù)

處理的具體實現(xiàn)步驟

（1）通過key獲取和用戶連接的通道（相當于輸入流）

（2）獲取通道的數(shù)據(jù)并打印

（3）將數(shù)據(jù)轉(zhuǎn)發(fā)給其他在線用戶

public void listener() {
    while (true) {
        try {
            if (selector.select(1000) == 0) {
                continue;
            }
            //獲得所有有事件的key
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                //如果當前key是處理鏈接類型
                if (key.isAcceptable()) {
                    SocketChannel socketChannel =
                    serverSocketChannel.accept();
                    socketChannel.configureBlocking(false);
                    socketChannel.register(selector, SelectionKey.OP_READ);
                }
                // 當前鏈接是讀數(shù)據(jù)類型
                if (key.isReadable()) {
                    readData(key);
                }
                iterator.remove();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2.4 群發(fā)數(shù)據(jù)實現(xiàn)

數(shù)據(jù)群發(fā)實現(xiàn)步驟

（1）當前在線用戶實際上就是selector中所有注冊的key，也就是在線的用戶

（2）通過key拿到和用戶的鏈接講消息轉(zhuǎn)發(fā)出去

/**
* 監(jiān)聽客戶端操作
*/
/**
* 讀取數(shù)據(jù)并群發(fā)給所有的用戶
* @param key
*/
private void readData(SelectionKey key) {
    try {
        if (key.isReadable()) {
            SocketChannel channel = (SocketChannel) key.channel();
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            channel.read(byteBuffer);
            String s = new String(byteBuffer.array());
            // 寫到其他所有客戶端
            sendData2All(s);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

2.5 啟動服務(wù)端

public static void main(String[] args) {
    ChatServer chatServer = new ChatServer();
    chatServer.listener();
}

3. 客戶端實現(xiàn)

客戶端實現(xiàn)

（1）首先創(chuàng)建SocketChannel對象并鏈接到具體的服務(wù)器

（2）將通道注冊到selector中

（3）開啟一個新的線程監(jiān)聽selector中所有key的事件

（4）在主線程中循環(huán)阻塞獲取用戶的輸入 

public class ChatClient {
    public static void main(String[] args) throws Exception {
    // 客戶端代碼, 建立連接
        Selector selector = Selector.open();
        SocketChannel socketChannel = SocketChannel.open(new
        InetSocketAddress("127.0.0.1", 8888));
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ);
        // 開啟一個新的線程輪詢當前客戶是否有可讀消息
        new Thread(() -> {
            while (true) {
                try {
                    int select = selector.select(1000);
                    // 有可讀消息進行解析打印
                    if (select > 0) {
                        for (SelectionKey key : selector.selectedKeys()) {
                            if (key.isReadable()) {
                                SocketChannel channel = (SocketChannel)
                                key.channel();
                                ByteBuffer byteBuffer =
                                ByteBuffer.allocate(1024);
                                channel.read(byteBuffer);
                                System.out.println(":==:" + new
                                String(byteBuffer.array()));
                                // 寫到其他所有客戶端
                                System.out.println(new
                                String(byteBuffer.array()));
                            }
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }   
            }
        }).start();
        // 主線程中循環(huán)獲取用戶輸入的聊天消息
        while(true) {
            Scanner scanner = new Scanner(System.in);
            //發(fā)送用戶的消息
            socketChannel.write(ByteBuffer.wrap(scanner.nextLine().getBytes()));
        }
    }
}

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