NIO网络编程实战之简单多人聊天室

NIO网络编程实战
利用NIO编程知识，实现多人聊天室。

1. NIO编程实现步骤

第一步：创建Selector

第二步：创建ServerSocketChannel，并绑定监听端口

第三步：将Channel设置为非阻塞模式

第四步：将Channel注册到Selector上，监听连接事件

第五步：循环调用Selector的select方法，检测就绪情况

第六步：调用selectedKeys方法获取就绪channel集合

第七步：判断就绪事件种类，调用业务处理方法

第八步：根据业务需要决定是否再次注册监听事件，重复执行第三步操作

2. NIO网络编程实战

利用NIO编程知识，实现多人聊天室。

2.1 程序结构目录

2.2 服务器端程序

package com.xuxin.niochatroom;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;/*** NIO服务器端*/
public class NioServer {/*** 启动*/public void start() throws IOException {// 1. 创建SelectorSelector selector = Selector.open();// 2. 通过ServerSocketChannel创建channel通道ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();// 3. 为channel通道绑定监听端口serverSocketChannel.bind(new InetSocketAddress(8000));// 4. 设置channel为非阻塞模式serverSocketChannel.configureBlocking(false);// 5. 将channel注册到selector上，监听连接事件serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);System.out.println("服务器启动成功！");// 6. 循环等待新接入的连接for (;;) {// 获取可用channel的数量int readyChannels = selector.select();if (readyChannels == 0) {continue;}// 获取可用channel的集合Set<SelectionKey> selectionKeys = selector.selectedKeys();Iterator iterator = selectionKeys.iterator();while(iterator.hasNext()) {// selectionKey实例SelectionKey selectionKey = (SelectionKey) iterator.next();// 移除Set中的当前selectionKeyiterator.remove();// 7. 根据就绪状态，调用对应方法处理业务逻辑// 如果是 接入事件if (selectionKey.isAcceptable()) {acceptHandler(serverSocketChannel, selector);}// 如果是 可读事件if (selectionKey.isReadable()) {readHandler(selectionKey, selector);}}}}/*** 接入事件处理器*/private void acceptHandler(ServerSocketChannel serverSocketChannel,Selector selector) throws IOException {// 如果要是接入事件，创建socketChannelSocketChannel socketChannel = serverSocketChannel.accept();// 将socketChannel设置为非阻塞工作模式socketChannel.configureBlocking(false);// 将channel注册到selector上，监听 可读事件socketChannel.register(selector, SelectionKey.OP_READ);// 回复客户端提示信息socketChannel.write(Charset.forName("UTF-8").encode("你与聊天室里其他人都不是朋友关系，请注意隐私安全"));}/*** 可读事件处理器*/private void readHandler(SelectionKey selectionKey, Selector selector)throws IOException {// 要从selectionKey中获取到已经就绪的channelSocketChannel socketChannel = (SocketChannel) selectionKey.channel();// 创建bufferByteBuffer byteBuffer = ByteBuffer.allocate(1024);// 循环读取客户端请求信息String request = "";while (socketChannel.read(byteBuffer) > 0) {// 切换buffer为读模式byteBuffer.flip();// 读取buffer中的内容request += Charset.forName("UTF-8").decode(byteBuffer);}// 将channel再次注册到selector上，监听他的可读事件socketChannel.register(selector, selectionKey.OP_READ);// 将客户端发送的请求信息 广播给其他客户端if (request.length() > 0) {// 广播给其他客户端broadCast(selector, socketChannel, request);}}/*** 广播给其他客户端*/private void broadCast(Selector selector, SocketChannel sourceChannel, String request) {// 获取到所有已接入的客户端channelSet<SelectionKey> selectionKeySet = selector.keys();// 循环向所有channel广播信息selectionKeySet.forEach(selectionKey -> {Channel targetChannel = selectionKey.channel();// 剔除发消息的客户端if ((targetChannel instanceof SocketChannel) && (targetChannel != sourceChannel)) {try {// 将信息群发给target的客户端((SocketChannel) targetChannel).write(Charset.forName("UTF-8").encode(request));} catch (IOException e) {e.printStackTrace();}}});}/*** 主程序* @param args*/public static void main(String[] args) throws IOException {NioServer nioServer = new NioServer();nioServer.start();}
}

2.3 客户端程序

package com.xuxin.niochatroom;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Scanner;/*** NIO客户端*/
public class NioClient {/*** 启动*/public void start(String nickName) throws IOException {// 连接服务器SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 8000));// 接收服务器端响应// 创建线程，专门负责接收服务器端的响应数据// selector socketChannel 注册Selector selector = Selector.open();socketChannel.configureBlocking(false);socketChannel.register(selector, SelectionKey.OP_READ);new Thread(new NioClientHandler(selector)).start();// 向服务器端发送数据Scanner scanner = new Scanner(System.in);while (scanner.hasNextLine()) {String request = scanner.nextLine();if ((request != null) && (request.length() > 0)) {socketChannel.write(Charset.forName("UTF-8").encode(nickName + " : " + request));}}}
}

2.4 客户端处理服务器端响应的线程

package com.xuxin.niochatroom;import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;public class NioClientHandler implements Runnable {private Selector selector;public NioClientHandler(Selector selector) {this.selector = selector;}@Overridepublic void run() {try {// 1. 循环等待服务器端响应for (; ; ) {// 获取可用channel的数量int readyChannels = selector.select();if (readyChannels == 0) {continue;}// 获取可用channel的集合Set<SelectionKey> selectionKeys = selector.selectedKeys();Iterator iterator = selectionKeys.iterator();while (iterator.hasNext()) {// selectionKey实例SelectionKey selectionKey = (SelectionKey) iterator.next();// 移除Set中的当前selectionKeyiterator.remove();// 7. 根据就绪状态，调用对应方法处理业务逻辑// 如果是 可读事件if (selectionKey.isReadable()) {readHandler(selectionKey, selector);}}}} catch (IOException e) {e.printStackTrace();}}/*** 可读事件处理器*/private void readHandler(SelectionKey selectionKey, Selector selector)throws IOException {// 要从selectionKey中获取到已经就绪的channelSocketChannel socketChannel = (SocketChannel) selectionKey.channel();// 创建bufferByteBuffer byteBuffer = ByteBuffer.allocate(1024);// 循环读取服务器端的响应数据String reponse = "";while (socketChannel.read(byteBuffer) > 0) {// 切换buffer为读模式byteBuffer.flip();// 读取buffer中的内容reponse += Charset.forName("UTF-8").decode(byteBuffer);}// 将channel再次注册到selector上，监听他的可读事件socketChannel.register(selector, selectionKey.OP_READ);// 将服务器端的响应数据打印到本地if (reponse.length() > 0) {System.out.println(":: " + reponse);}}
}

2.5 测试

2.5.1 创建用于测试的客户端类

ClientA：

package com.xuxin.niochatroom;import java.io.IOException;public class ClientA {public static void main(String[] args) throws IOException {new NioClient().start("ClientA");}
}

ClientB：

package com.xuxin.niochatroom;import java.io.IOException;public class ClientB {public static void main(String[] args) throws IOException {new NioClient().start("ClientB");}
}

ClientC：

package com.xuxin.niochatroom;import java.io.IOException;public class ClientC {public static void main(String[] args) throws IOException {new NioClient().start("ClientC");}
}

2.5.2 结果

启动服务器端

启动ClientA、ClientB、ClientC，并先由ClientA开始输入聊天信息，再由ClientB开始输入聊天信息，最后由ClientC开始输入聊天信息

2.6 NIO网络编程缺陷

麻烦

NIO类库和API繁杂。需要了解ServerSocketChannel、SocketChannel、ByteBuffer等核心类库的使用

问题

可靠性能力补齐，工作量和难度都非常大。
客户端的断连、重连、网络闪断、失败缓存、网络阻塞和异常码流等问题。

有坑

Selector空轮询，导致CPU100%。