3、nio中的selector使用
通过编写一个客户端和服务器端的例子来熟悉selector的使用
服务端逻辑：
1. 绑定一个端口号
2. channel注册到selector中
3. 用死循环来监听如果有时间发生，遍历selectionKey set
4. 判断发生的事件类型，前面会注册accept事件，如果发生accept事件，那么注册读事件，同时清除selectionKey set 中的当前元素。、
5. 接收事件时，将channel保存下来。
6. 发生读事件时，说明有信息，发过来了，那么将消息，转发给所有的客户端。然后清除自身的事件。
1 import java.io.IOException; 2 import java.net.InetSocketAddress; 3 import java.net.ServerSocket; 4 import java.nio.ByteBuffer; 5 import java.nio.channels.SelectionKey; 6 import java.nio.channels.Selector; 7 import java.nio.channels.ServerSocketChannel; 8 import java.nio.channels.SocketChannel; 9 import java.nio.charset.Charset; 10 import java.util.*; 11 12 public class NioServer { 13 14 private static HashMap<String, SocketChannel> clientMap = new HashMap<String, SocketChannel>(); 15 16 public static void main(String[] args) throws IOException { 17 ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); 18 serverSocketChannel.configureBlocking(false); 19 20 ServerSocket serverSocket = serverSocketChannel.socket(); 21 serverSocket.bind(new InetSocketAddress(8899)); 22 23 Selector selector = Selector.open(); 24 25 serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); 26 27 while(true) { 28 int number = selector.select(); 29 // System.out.println("number:" + number); 30 Set<SelectionKey> selectionKeySet = selector.selectedKeys(); 31 32 Iterator<SelectionKey> iterable = selectionKeySet.iterator(); 33 34 if(number > 0 ) { 35 while(iterable.hasNext()) { 36 SelectionKey selectionKey = iterable.next(); 37 38 if(selectionKey.isAcceptable()) {//如果是可接收连接的 39 ServerSocketChannel ssc = (ServerSocketChannel) selectionKey.channel(); 40 SocketChannel socketChannel = ssc.accept(); 41 socketChannel.configureBlocking(false); 42 43 socketChannel.register(selector, SelectionKey.OP_READ);//注册读事件 44 45 clientMap.put(UUID.randomUUID() + "", socketChannel);//保存下channel 46 47 iterable.remove(); 48 } else if(selectionKey.isReadable()){//可读的 49 SocketChannel socketChannel = (SocketChannel) selectionKey.channel(); 50 ByteBuffer byteBuffer = ByteBuffer.allocate(1024); 51 52 int readCount = socketChannel.read(byteBuffer); 53 54 //这里本该用while 55 if(readCount > 0 ) {//读取到数据，就写回到其他客户端 56 byteBuffer.flip(); 57 58 Charset charset = Charset.forName("UTF-8"); 59 String receiveStr = new String(charset.decode(byteBuffer).array()); 60 61 System.out.println(socketChannel + " receive msg :" + receiveStr); 62 63 String sendKey = ""; 64 65 for(Map.Entry<String, SocketChannel> entry : clientMap.entrySet()) {//第一遍遍历找到发送者 66 if(socketChannel == entry.getValue()) { 67 sendKey = entry.getKey(); 68 break; 69 } 70 } 71 72 for (Map.Entry<String, SocketChannel> entry: clientMap.entrySet() ) {//给每个保存的连接，都发送消息 73 ByteBuffer writeBuffer = ByteBuffer.allocate(1024); 74 writeBuffer.put((sendKey + ":" + receiveStr).getBytes()); 75 76 writeBuffer.flip(); 77 entry.getValue().write(writeBuffer); 78 } 79 } 80 iterable.remove();//这个 删除很关键 每次循环完selectionKeySet ，一定要清楚事件，不然肯定会影响下一次的事件触发，或者直接不触发下次的事件 81 } 82 } 83 } 84 85 } 86 } 87 }
客户端逻辑
1. 建立socketChannel 连接到对应的端口
2. 新建selector对象，然后把socketChannel注册到selector上
3. 建立死循环 ，监听是否有事件发生，若有，则遍历seletionKey set ,
4. 判断发生的事件是什么，
5. 如果是连接事件 ，做对应的连接处理，注册读事件
判断是否在等待连接 ，在进程中 if (channel.isConnectionPending()) { channel.finishConnect(); 完成连接，这里是阻塞的
6. 如果发生了读事件，读取数据
1 import java.io.BufferedReader; 2 import java.io.InputStream; 3 import java.io.InputStreamReader; 4 import java.net.InetSocketAddress; 5 import java.nio.ByteBuffer; 6 import java.nio.channels.SelectionKey; 7 import java.nio.channels.Selector; 8 import java.nio.channels.SocketChannel; 9 import java.time.LocalDateTime; 10 import java.util.Iterator; 11 import java.util.Set; 12 import java.util.concurrent.Executor; 13 import java.util.concurrent.ExecutorService; 14 import java.util.concurrent.Executors; 15 import java.util.concurrent.ThreadFactory; 16 17 public class NioClient { 18 19 public static void main(String[] args) { 20 try{ 21 SocketChannel socketChannel = SocketChannel.open(); 22 socketChannel.configureBlocking(false); 23 socketChannel.connect(new InetSocketAddress(8899));//服务端就是bind 然后accept serverSocketChannel 24 25 Selector selector = Selector.open(); 26 27 socketChannel.register(selector, SelectionKey.OP_CONNECT);//注册连接事件 28 29 while(true) { 30 int number = selector.select(); 31 32 if(number > 0) { 33 Set<SelectionKey> selectionKeySet = selector.selectedKeys(); 34 35 Iterator<SelectionKey> iterable = selectionKeySet.iterator(); 36 while(iterable.hasNext()) {//有事件发生 37 SelectionKey selectionKey = iterable.next(); 38 39 SocketChannel client = (SocketChannel) selectionKey.channel(); 40 if(selectionKey.isConnectable()) {//判断 selectionkey 状态 可连接的 41 if(client.isConnectionPending()) {//是否在准备连接的进程中 42 client.finishConnect();//这里会阻塞，如果连接未建立，抛异常 ， 43 44 ByteBuffer byteBuffer = ByteBuffer.allocate(1024); 45 46 byteBuffer.put((LocalDateTime.now() + "，连接成功").getBytes()); 47 byteBuffer.flip(); 48 client.write(byteBuffer); 49 50 ExecutorService executorService = Executors.newSingleThreadExecutor(Executors.defaultThreadFactory()); 51 52 executorService.submit(() -> {//起一个新的线程，去接收控制台的输入 ，不影响其他线程 53 while(true) { 54 try{ 55 byteBuffer.clear(); 56 InputStreamReader inputStreamReader = new InputStreamReader(System.in); 57 BufferedReader bufferedReader = new BufferedReader(inputStreamReader); 58 59 byteBuffer.put(bufferedReader.readLine().getBytes()); 60 byteBuffer.flip(); 61 client.write(byteBuffer); 62 63 }catch (Exception e) { 64 e.printStackTrace(); 65 } 66 } 67 }); 68 } 69 70 iterable.remove();//这个事件清楚，很关键 71 client.register(selector, SelectionKey.OP_READ);//注册读事件 72 } else if(selectionKey.isReadable()){//可读取 73 SocketChannel socketChannel1 = (SocketChannel) selectionKey.channel(); 74 ByteBuffer readBuffer = ByteBuffer.allocate(1024); 75 76 int readCount = socketChannel.read(readBuffer); 77 if(readCount > 0) { 78 String receiveMsg = new String(readBuffer.array()); 79 System.out.println("receiveMsg : " + receiveMsg); 80 } 81 82 iterable.remove(); 83 } 84 85 } 86 } 87 } 88 89 90 91 92 }catch (Exception e ) { 93 e.printStackTrace(); 94 } 95 96 97 } 98 }
