04-Java NIO 编程应用实例-多人群聊系统

需求

编写一个NIO群聊系统,实现服务器端和客户端之间的数据简单通讯,非阻塞
实现多人群聊

服务器端: 可以监测用户上线, 离线, 并实现消息转发功能
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)

目的: 进一步了解NIO非阻塞网络编程机制
示意图分析和代码

示意图

编码

Server

package com.dance.netty.nio.demo.groupchat;

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

public class GroupChatServer {

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

    /**
     * 服务器 Channel
     */
    private ServerSocketChannel serverSocketChannel;

    /**
     * 服务器端口号
     */
    private static final int PORT = 6667;

    public GroupChatServer() {
        try {
            // 初始化参数
            selector = Selector.open();
            serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.socket().bind(new InetSocketAddress(PORT));
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 监听
     */
    public void listener() {
        for (; ; ) {
            try {
                int eventCount = selector.select(10000);
                // 有事件要处理
                if (eventCount > 0) {
                    Set<SelectionKey> selectionKeys = selector.selectedKeys();
                    Iterator<SelectionKey> iterator = selectionKeys.iterator();
                    while (iterator.hasNext()) {
                        SelectionKey selectionKey = iterator.next();
                        if (selectionKey.isAcceptable()) {
                            SocketChannel socketChannel = serverSocketChannel.accept();
                            socketChannel.configureBlocking(false);
                            socketChannel.register(selector, SelectionKey.OP_READ, ByteBuffer.allocate(1024));
                            System.out.println("用户: " + socketChannel.getRemoteAddress().toString().substring(1) + " 上线了");
                        }
                        if (selectionKey.isReadable()) {
                            readData(selectionKey);
                        }
                        iterator.remove();
                    }
                }
                System.out.println("等待事件发生......");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 处理读事件
     *
     * @param selectionKey channel id
     */
    public void readData(SelectionKey selectionKey) {
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
        ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
        try {
            int readSize = 0;
            int readSizeCount = 0;
            byte[] dist = new byte[0];
            // 为了处理大于1024的数据 采用循环读取
            while ((readSize = socketChannel.read(buffer)) > 0) {
                readSizeCount += readSize;
                byte[] src = buffer.array();
                buffer.flip();
                // 为了防止汉子断裂,采用字节数组合并
                dist = mergerByteArray(dist, dist.length, src, buffer.limit());
            }
            String message = new String(dist);
            System.out.println("用户: " + socketChannel.getRemoteAddress().toString().substring(1) + " , 发送: " + message);
            sendMessageToOtherClients(message, selectionKey);
        } catch (IOException e) {
//            e.printStackTrace();
            try {
                System.out.println("用户: " + socketChannel.getRemoteAddress().toString().substring(1) + " 离线了");
                // 从selector中取消注册
                selectionKey.cancel();
                // 关闭通道
                socketChannel.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    /**
     * 发送给其他客户端
     *
     * @param message      消息
     * @param selectionKey form client key
     */
    public void sendMessageToOtherClients(String message, SelectionKey selectionKey) {
        // 获取所有的在线客户端
        Set<SelectionKey> keys = selector.keys();
        // 排除自己
        keys.stream().filter(key -> !key.equals(selectionKey)).filter(key -> key.channel() instanceof SocketChannel).forEach(key -> {
            SocketChannel socketChannel = (SocketChannel) key.channel();
            // 因为不知道 字节数组的长度 所以采用新的Buffer
            ByteBuffer wrap = ByteBuffer.wrap(message.getBytes(StandardCharsets.UTF_8));
            try {
                int write = socketChannel.write(wrap);
                System.out.println("输出数据给:"+socketChannel.getRemoteAddress().toString().substring(1));
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
    }

    /**
     * byte array merger
     *
     * @param left        左边的字节数组
     * @param leftLength  要合并的结束坐标
     * @param right       右边的字节数组
     * @param rightLength 要合并的结束坐标
     * @return 合并后的字节数组
     */
    public byte[] mergerByteArray(byte[] left, int leftLength, byte[] right, int rightLength) {
        byte[] bytes = new byte[leftLength + rightLength];
        System.arraycopy(left, 0, bytes, 0, leftLength);
        System.arraycopy(right, 0, bytes, leftLength, rightLength);
        return bytes;
    }

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

}

client

package com.dance.netty.nio.demo.groupchat;

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.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.Scanner;

public class GroupChatClient {

    private final String IP = "127.0.0.1";

    private final int PORT = 6667;

    private Selector selector;

    private SocketChannel socketChannel;

    private String username;

    public GroupChatClient() {
        try {
            selector = Selector.open();
            socketChannel = SocketChannel.open(new InetSocketAddress(IP, PORT));
            socketChannel.configureBlocking(false);
            socketChannel.register(selector, SelectionKey.OP_READ);
            username = socketChannel.getLocalAddress().toString().substring(1);
            System.out.println(username + " init success......");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void sendMessage(String message) {
        message = username + " : " + message;
        try {
            int write = socketChannel.write(ByteBuffer.wrap(message.getBytes(StandardCharsets.UTF_8)));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void readMessage() {
        int select = 0;
        try {
            select = selector.select();
            if (select > 0) {
                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                while (iterator.hasNext()) {
                    SelectionKey selectionKey = iterator.next();
                    if (selectionKey.isReadable()) {
                        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        int read = socketChannel.read(buffer);
                        if (read > 0) {
                            buffer.flip();
                            String msg = new String(buffer.array(), 0, buffer.limit());
                            System.out.println(msg);
                        }
                    }
                    iterator.remove();
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        GroupChatClient groupChatClient = new GroupChatClient();
        new Thread(() -> {
            while (true) {
                groupChatClient.readMessage();
            }
        }).start();

        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextLine()){
            String s = scanner.nextLine();
            groupChatClient.sendMessage(s);
        }
    }

}