NIO实现群聊系统

简单的编写一个群聊系统，实现的功能如下：

1. 实现服务器端和客户端的群聊系统，实现非阻塞方式的数据简单通讯

2. 实现多人聊天

3. 服务器端可以实现感应到用户上线、离线，并实现消息转发

4. 客户端：通过channel可以无阻塞发送消息给其他用户，同时可以接受其他用户发送的消息(由服务器转发得到)

5. 在此基础上改造下实现单聊天，由服务器转发(也就是转发的时候转发给特定的用户)

1. 群聊实现

1. 服务器端代码

package nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;


public class GroupChatServer {

    /**
     * Selector 选择器
     */
    private Selector selector;

    /**
     * ServerSocketChannel
     */
    private ServerSocketChannel serverSocketChannel;

    /**
     * 端口
     */
    private static final int PORT = 6667;

    public GroupChatServer() {
        try {
            selector = Selector.open();
            serverSocketChannel = ServerSocketChannel.open();
            // 绑定端口
            serverSocketChannel.socket().bind(new InetSocketAddress(PORT));
            // 设置非阻塞模式
            serverSocketChannel.configureBlocking(false);
            // 注册连接请求事件
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 监听
     */
    public void listen() {
        System.out.println("监听线程: " + Thread.currentThread().getName());

        try {
            while (true) {
                int count = selector.select();
                // 有事件处理
                if (count > 0) {
                    // 处理监听到的事件
                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    SelectionKey key = null;
                    while (iterator.hasNext()) {
                        key = iterator.next();
                        // 连接请求事件
                        if (key.isAcceptable()) {
                            SocketChannel socketChannel = serverSocketChannel.accept();
                            // 设置非阻塞
                            socketChannel.configureBlocking(false);
                            // 注册读取事件
                            socketChannel.register(selector, SelectionKey.OP_READ);
                            // 提示
                            System.out.println(socketChannel.getRemoteAddress() + " 上线 ");
                        }

                        // 数据读取事件
                        if (key.isReadable()) {
                            readData(key);
                        }

                        // 删除当前的key，防止重复处理
                        iterator.remove();
                    }
                }
            }
        } catch (Throwable e) {
            e.printStackTrace();
        }
    }

    private void readData(SelectionKey key) {
        SocketChannel channel = null;
        try {
            channel = (SocketChannel) key.channel();
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            int read = channel.read(byteBuffer);
            if (read > 0) {
                //把缓存区的数据转成字符串
                String msg = new String(byteBuffer.array());
                System.out.println("form 客户端: " + msg);

                //向其它的客户端转发消息(去掉自己), 专门写一个方法来处理
                sendInfoToOtherClients(msg, channel);
            }
        } catch (Exception e) {
            e.printStackTrace();

            try {
                System.out.println(channel.getRemoteAddress() + " 离线了..");
                //取消注册
                key.cancel();
                //关闭通道
                channel.close();
            } catch (IOException e2) {
                e2.printStackTrace();
            }
        }
    }

    private void sendInfoToOtherClients(String msg, SocketChannel channel) throws IOException {
        System.out.println("服务器转发消息中...");

        for (SelectionKey key : selector.keys()) {
            // 通过 key  取出对应的 SocketChannel
            Channel targetChannel = key.channel();
            // 排除掉自己
            if (targetChannel instanceof SocketChannel && targetChannel != channel) {
                // 转型
                SocketChannel dest = (SocketChannel) targetChannel;
                // 将msg 存储到buffer
                ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
                // 将buffer 的数据写入 通道
                dest.write(buffer);
                System.out.println("转发给： " + dest.getRemoteAddress());
            }
        }
    }

    public static void main(String[] args) {
        //创建服务器对象
        GroupChatServer groupChatServer = new GroupChatServer();
        groupChatServer.listen();
    }
}

2. 客户端代码：

package nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Scanner;

public class GroupChatClient {

    /**
     * 服务器地址
     */
    private final String HOST = "127.0.0.1";
    /**
     * 服务器端口
     */
    private final int PORT = 6667;

    private Selector selector;
    private SocketChannel socketChannel;
    private String username;

    public GroupChatClient() {
        try {
            selector = Selector.open();
            // 连接服务器
            socketChannel = SocketChannel.open(new InetSocketAddress(HOST, PORT));
            // 设置非阻塞
            socketChannel.configureBlocking(false);
            // 将channel 注册到selector， 注册读取事件
            socketChannel.register(selector, SelectionKey.OP_READ);
            // 得到username
            username = socketChannel.getLocalAddress().toString().substring(1);
            System.out.println(username + " is ok!");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void sendMsg(String msg) {
        msg = username + " 说：" + msg;
        try {
            socketChannel.write(ByteBuffer.wrap(msg.getBytes()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void readMsg() {
        try {
            int count = selector.select();
            // 有可用的通道
            if (count > 0) {
                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                while (iterator.hasNext()) {
                    SelectionKey key = iterator.next();
                    if (key.isReadable()) {
                        SocketChannel channel = (SocketChannel) key.channel();
                        // 开启一个buffer
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        channel.read(buffer);
                        //把读到的缓冲区的数据转成字符串
                        String msg = new String(buffer.array());
                        System.out.println(msg.trim());
                    }
                }

                // 删除当前的selectionKey, 防止重复操作
                iterator.remove();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        GroupChatClient chatClient = new GroupChatClient();
        // 启动一个线程, 每3秒，读取从服务器发送数据
        new Thread() {
            public void run() {
                while (true) {
                    chatClient.readMsg();
                    try {
                        Thread.currentThread().sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();

        //发送数据给服务器端
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            chatClient.sendMsg(s);
        }
    }
}

3.测试： 启动一个服务端，两个客户端

服务器端控制台如下：

监听线程: main
/127.0.0.1:51500 上线 
/127.0.0.1:51687 上线 

(1) 客户端51500 发送消息

127.0.0.1:51500 is ok!
hello 中国
hello China

（2） 查看服务器端日志

监听线程: main
/127.0.0.1:51500 上线 
/127.0.0.1:51687 上线 
form 客户端: 127.0.0.1:51500 说：hello 中国                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
服务器转发消息中...
转发给： /127.0.0.1:51687
form 客户端: 127.0.0.1:51500 说：hello China                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
服务器转发消息中...
转发给： /127.0.0.1:51687

(3) 查看51687 日志

127.0.0.1:51687 is ok!
127.0.0.1:51500 说：hello 中国
127.0.0.1:51500 说：hello China

补充： selectedKeys和keys 的区别： 

(1) selectedKeys() ： 向selected第一次注册的，获取后要删掉的，没连接、发送数据一次就会注入一个selectkey。也可以理解为这个是发生数据的SelectionKey 集合，处理完就要删掉。

(2) 当前连接的所有keys。可以理解为这个是 所有存在的SelectionKey 集合。

对应到SelectorImpl 如下属性：

    private Set<SelectionKey> publicKeys;
    private Set<SelectionKey> publicSelectedKeys;

2.单聊实现

 单聊其实就是在上面进行改造，将消息经服务器转发到特定的channel。我们改造一下，将用户信息存到本地的txt文件中，客户端需要先选择用户再编写消息

1. 服务器端代码

package nio;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;


public class GroupChatServer {

    /**
     * Selector 选择器
     */
    private Selector selector;

    /**
     * ServerSocketChannel
     */
    private ServerSocketChannel serverSocketChannel;

    /**
     * 端口
     */
    private static final int PORT = 6667;

    public GroupChatServer() {
        try {
            selector = Selector.open();
            serverSocketChannel = ServerSocketChannel.open();
            // 绑定端口
            serverSocketChannel.socket().bind(new InetSocketAddress(PORT));
            // 设置非阻塞模式
            serverSocketChannel.configureBlocking(false);
            // 注册连接请求事件
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

            // 添加* 代表发送给所有用户
            addUser("*");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 监听
     */
    public void listen() {
        System.out.println("监听线程: " + Thread.currentThread().getName());

        try {
            while (true) {
                int count = selector.select();
                // 有事件处理
                if (count > 0) {
                    // 处理监听到的事件
                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    SelectionKey key = null;
                    while (iterator.hasNext()) {
                        key = iterator.next();
                        // 连接请求事件
                        if (key.isAcceptable()) {
                            SocketChannel socketChannel = serverSocketChannel.accept();
                            // 设置非阻塞
                            socketChannel.configureBlocking(false);
                            // 注册读取事件
                            socketChannel.register(selector, SelectionKey.OP_READ);
                            // 提示
                            System.out.println(socketChannel.getRemoteAddress() + " 上线 ");

                            // 加到保持姓名的集合
                            addUser(socketChannel.getRemoteAddress().toString());
                        }

                        // 数据读取事件
                        if (key.isReadable()) {
                            readData(key);
                        }

                        // 删除当前的key，防止重复处理
                        iterator.remove();
                    }
                }
            }
        } catch (Throwable e) {
            e.printStackTrace();
        }
    }

    private void readData(SelectionKey key) {
        SocketChannel channel = null;
        try {
            channel = (SocketChannel) key.channel();
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            int read = channel.read(byteBuffer);
            if (read > 0) {
                //把缓存区的数据转成字符串
                String msg = new String(byteBuffer.array());
                System.out.println("form 客户端: " + msg);

                //向其它的客户端转发消息(去掉自己), 专门写一个方法来处理
                sendInfoToOtherClients(msg, channel);
            }
        } catch (Exception e) {
            e.printStackTrace();

            try {
                System.out.println(channel.getRemoteAddress() + " 离线了..");
                //取消注册
                key.cancel();
                //关闭通道
                channel.close();

                // 从姓名集合删除
                removeUser(channel.getRemoteAddress().toString());
            } catch (IOException e2) {
                e2.printStackTrace();
            }
        }
    }

    private void sendInfoToOtherClients(String msg, SocketChannel channel) throws IOException {
        System.out.println("服务器转发消息中...");

        for (SelectionKey key : selector.keys()) {
            // 通过 key  取出对应的 SocketChannel
            Channel targetChannel = key.channel();
            // 排除掉自己
            if (targetChannel instanceof SocketChannel && targetChannel != channel) {
                // 转型
                SocketChannel dest = (SocketChannel) targetChannel;
                // 解析消息 sendUsername#@#msg
                String[] split = StringUtils.split(msg, "#@#");
                String remoteAddress = dest.getRemoteAddress().toString();
                String sendTarget = split[0];
                if (!"*".equals(sendTarget) && !sendTarget.equals(remoteAddress)) {
                    continue;
                }

                String sendMsg = split[1];
                // 将msg 存储到buffer
                ByteBuffer buffer = ByteBuffer.wrap(sendMsg.getBytes());
                // 将buffer 的数据写入 通道
                dest.write(buffer);
                System.out.println("转发给： " + dest.getRemoteAddress());
            }
        }
    }

    // 用户存到本地文件内部
    public static void addUser(String username) {
        try {
            String encoding = "utf-8";
            File file = new File("F:/user.txt");
            if (!file.exists()) {
                file.createNewFile();
            }

            List<String> list = IOUtils.readLines(new FileInputStream(file), encoding);
            if (!list.contains(username)) {
                list.add(username);
            }
            IOUtils.writeLines(list, null, new FileOutputStream(file));
        } catch (Exception exception) {
            // ignore
        }
    }

    // 用户存到本地文件内部
    public static void removeUser(String username) {
        try {
            String encoding = "utf-8";
            File file = new File("F:/user.txt");
            if (!file.exists()) {
                file.createNewFile();
            }

            List<String> list = IOUtils.readLines(new FileInputStream(file), encoding);
            list.remove(username);
            IOUtils.writeLines(list, encoding, new FileOutputStream(file));
        } catch (Exception exception) {
            // ignore
        }
    }

    public static List<String> listAllClient() {
        String encoding = "utf-8";
        File file = new File("F:/user.txt");
        try {
            return IOUtils.readLines(new FileInputStream(file), encoding);
        } catch (IOException e) {
        }

        return Collections.emptyList();
    }

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

2. 客户端代码

package nio;

import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class GroupChatClient {

    /**
     * 服务器地址
     */
    private final String HOST = "127.0.0.1";
    /**
     * 服务器端口
     */
    private final int PORT = 6667;

    private Selector selector;
    private SocketChannel socketChannel;
    private String username;

    public GroupChatClient() {
        try {
            selector = Selector.open();
            // 连接服务器
            socketChannel = SocketChannel.open(new InetSocketAddress(HOST, PORT));
            // 设置非阻塞
            socketChannel.configureBlocking(false);
            // 将channel 注册到selector， 注册读取事件
            socketChannel.register(selector, SelectionKey.OP_READ);
            // 得到username
            username = socketChannel.getLocalAddress().toString().substring(1);
            System.out.println(username + " is ok!");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void sendMsg(String msg, String target) {
        msg = username + ":" + msg;
        msg = target + "#@#" + msg;
        try {
            socketChannel.write(ByteBuffer.wrap(msg.getBytes()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void readMsg() {
        try {
            int count = selector.select();
            // 有可用的通道
            if (count > 0) {
                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                while (iterator.hasNext()) {
                    SelectionKey key = iterator.next();
                    if (key.isReadable()) {
                        SocketChannel channel = (SocketChannel) key.channel();
                        // 开启一个buffer
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        channel.read(buffer);
                        //把读到的缓冲区的数据转成字符串
                        String msg = new String(buffer.array());
                        System.out.println(msg.trim());
                    }
                }

                // 删除当前的selectionKey, 防止重复操作
                iterator.remove();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        GroupChatClient chatClient = new GroupChatClient();
        // 启动一个线程, 每3秒，读取从服务器发送数据
        new Thread() {
            public void run() {
                while (true) {
                    chatClient.readMsg();
                    try {
                        Thread.currentThread().sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();

        //发送数据给服务器端
        Scanner scanner = new Scanner(System.in);
        while (true) {
            List<String> users = GroupChatServer.listAllClient();
            System.out.println("清选择发送的用户：(下标即可)");
            System.out.println(StringUtils.join(users, "
"));
            int userIndex = scanner.nextInt();
            if (userIndex >= users.size()) {
                System.out.println("输入有误");
                continue;
            }

            System.out.println("您选择发送给： " + users.get(userIndex) + ", 请输入消息： ");
            String s = scanner.next();
            chatClient.sendMsg(s, users.get(userIndex));
        }
    }
}

　　至此基于NIO基本简单的实现了群聊和单聊。