最近学习了一下NIO的一些api，做了简单的demo，感觉挺有意思的，有兴许的可以一起学习
NIO的上手难度感觉还挺高的，学习曲线有一些，毕竟之前已经习惯了BIO的操作了，一下切过来过来还挺困难的，理清楚了基本的几个概念就好理解多了，比如channel，buffer，selector，socketChannel，serverSocketChannel这几个弄清楚基本就可以看得懂NIO的api了，不然连api都很困难弄明白。我是从极客学院看的基础学习，然后写的简单的demo，只是demo而已，基础学习可以看一下。
服务端代码
package org.chao.nio;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
/**
* server 端
*
* @author xiezhengchao
* @since 2018/4/7 14:32
*/
public class ServerDemo{
private ByteBuffer readBuffer = ByteBuffer.allocateDirect(1024);
private ByteBuffer writeBuffer = ByteBuffer.allocateDirect(1024);
private Selector selector;
public ServerDemo() throws IOException{
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
ServerSocket serverSocket = serverSocketChannel.socket();
serverSocket.bind(new InetSocketAddress(8080));
System.out.println("listening on port 8080");
this.selector = Selector.open();;
// 绑定channel的accept
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
}
public static void main(String[] args) throws Exception{
new ServerDemo().go();
}
private void go() throws Exception{
// block api
while(selector.select()>0){
Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
while(iterator.hasNext()){
SelectionKey selectionKey = iterator.next();
iterator.remove();
// 新连接
if(selectionKey.isAcceptable()){
System.out.println("isAcceptable");
ServerSocketChannel server = (ServerSocketChannel)selectionKey.channel();
// 新注册channel
SocketChannel socketChannel = server.accept();
if(socketChannel==null){
continue;
}
socketChannel.configureBlocking(false);
// 注意！这里和阻塞io的区别非常大，在编码层面之前的等待输入已经变成了注册事件，这样我们就可以在等待的时候做别的事情，
// 比如监听更多的socket连接，也就是之前说了一个线程监听多个socket连接。这也是在编码的时候最直观的感受
socketChannel.register(selector, SelectionKey.OP_READ| SelectionKey.OP_WRITE);
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
buffer.put("hi new channel".getBytes());
buffer.flip();
socketChannel.write(buffer);
}
// 服务端关心的可读，意味着有数据从client传来了，根据不同的需要进行读取，然后返回
if(selectionKey.isReadable()){
System.out.println("isReadable");
SocketChannel socketChannel = (SocketChannel)selectionKey.channel();
readBuffer.clear();
socketChannel.read(readBuffer);
readBuffer.flip();
String receiveData= Charset.forName("UTF-8").decode(readBuffer).toString();
System.out.println("receiveData:"+receiveData);
// 把读到的数据绑定到key中
selectionKey.attach("server message echo:"+receiveData);
}
// 实际上服务端不在意这个，这个写入应该是client端关心的，这只是个demo,顺便试一下selectionKey的attach方法
if(selectionKey.isWritable()){
SocketChannel socketChannel = (SocketChannel)selectionKey.channel();
String message = (String) selectionKey.attachment();
if(message==null){
continue;
}
selectionKey.attach(null);
writeBuffer.clear();
writeBuffer.put(message.getBytes());
writeBuffer.flip();
while(writeBuffer.hasRemaining()){
socketChannel.write(writeBuffer);
}
}
}
}
}
}
客户端代码
package org.chao.nio;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
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.Charset;
import java.util.Iterator;
/**
* client 端
*
* @author xiezhengchao
* @since 2018/4/7 15:10
*/
public class ClientDemo{
private final ByteBuffer sendBuffer=ByteBuffer.allocate(1024);
private final ByteBuffer receiveBuffer=ByteBuffer.allocate(1024);
private Selector selector;
public ClientDemo()throws IOException{
SocketChannel socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress(InetAddress.getLocalHost(),8080));
socketChannel.configureBlocking(false);
System.out.println("与服务器的连接建立成功");
selector=Selector.open();
socketChannel.register(selector,SelectionKey.OP_READ | SelectionKey.OP_WRITE);
}
public static void main(String[] args) throws Exception{
final ClientDemo client=new ClientDemo();
Thread receiver=new Thread(client::receiveFromUser);
receiver.start();
client.talk();
}
private void talk()throws IOException {
while (selector.select() > 0 ){
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while (it.hasNext()){
SelectionKey key = it.next();
it.remove();
if (key.isReadable()) {
receive(key);
}
// 实际上只要注册了关心写操作，这个操作就一直被激活
if (key.isWritable()) {
send(key);
}
}
}
}
private void send(SelectionKey key)throws IOException{
SocketChannel socketChannel=(SocketChannel)key.channel();
synchronized(sendBuffer){
sendBuffer.flip(); //设置写
while(sendBuffer.hasRemaining()){
socketChannel.write(sendBuffer);
}
sendBuffer.compact();
}
}
private void receive(SelectionKey key)throws IOException{
SocketChannel socketChannel=(SocketChannel)key.channel();
socketChannel.read(receiveBuffer);
receiveBuffer.flip();
String receiveData=Charset.forName("UTF-8").decode(receiveBuffer).toString();
System.out.println("receive server message:"+receiveData);
receiveBuffer.clear();
}
private void receiveFromUser() {
BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(System.in));
try{
String msg;
while ((msg = bufferedReader.readLine()) != null){
synchronized(sendBuffer){
sendBuffer.put((msg+"\r\n").getBytes());
}
}
}catch(Exception e){
e.printStackTrace();
}
}
}
如果不启用客户端代码进行测试也可以用telnet命令进行测试telnet 127.0.0.1 8080
telnet命令测试服务端
