今天先介绍NioSocket的基本用法，实际使用一般会采用多线程，后面会介绍多线程的处理方法。
从jdk1.4开始，java增加了新的io模式--nio(new IO)，nio在底层采用了新的处理方式，极大地提高了IO效率。我们使用的Socket也属于IO的一种，nio提供了相应的工具：ServerSocketChanner和SocketChannel，它们分别对应ServerSocket和Socket。（不了解java socket可以百度下）
NioSocket包括三个重要的概念:Buffer（类似于送快递中的货物）、Channel（类似于送快递中的送货车）和Selector(类似于送快递中转站的分拣员)。原来的Socket类似于一个人送快递，没有形成产业链。
下面来看下代码：
服务端
package com.test;
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.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
public class NIOServer {
public static void main(String[] args) throws Exception {
//创建ServerSocketChannel，监听8080端口
ServerSocketChannel ssc = ServerSocketChannel.open();
ssc.socket().bind(new InetSocketAddress(8080));
//设置为非阻塞模式
ssc.configureBlocking(false);
//为ServerSocketChannel注册选择器
Selector selector = Selector.open();
/**
* 这里有四种SelectionKey分别表示接受请求操作、链接操作、读操作和写操作
* SelectionKey.OP_ACCEPT
* SelectionKey.OP_CONNECT
* SelectionKey.OP_READ
* SelectionKey.OP_WRITE
*/
ssc.register(selector, SelectionKey.OP_ACCEPT);
//创建处理器
Handler handler = new Handler(1024);//handler的创建在下面静态的内部类中
while(true){
//等待请求，每次等待阻塞3s，超过3s后线程继续向下运动，如果传入0或者不传入参数将一直阻塞
if(selector.select(3000) == 0){
System.out.println("等待请求超时....");
continue;
}
System.out.println("处理请求......");
//获取待处理的SelectionKey
Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
while(keyIter.hasNext()){
SelectionKey key = keyIter.next();
try {
//接收到链接请求时
if(key.isAcceptable()){
handler.handAccept(key);//改变Selector为读操作
}
//读数据
if(key.isReadable()){
handler.handlerRead(key);
}
} catch (Exception e) {
keyIter.remove();
continue;
}
//处理完成后，从待处理的SelectionKey迭代器中移除当前所使用的key
keyIter.remove();
}
}
}
public static class Handler{
private int bufferSize = 1024;
private String localCharset = "UTF-8";
public Handler() {}
public Handler(int bufferSize) {
this(bufferSize,null);
}
public Handler(String localCharset) {
this(-1,localCharset);
}
public Handler(int bufferSize, String localCharset) {
if(bufferSize>0){
this.bufferSize = bufferSize;
}
if(localCharset != null){
this.localCharset = localCharset;
}
}
public void handAccept(SelectionKey key) throws IOException {
SocketChannel sc = ((ServerSocketChannel)key.channel()).accept();
sc.configureBlocking(false);
sc.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(bufferSize));//改变Selector为读操作
}
public void handlerRead(SelectionKey key) throws IOException {
//获取channel
SocketChannel sc = (SocketChannel) key.channel();
//获取channel并重置
ByteBuffer buffer = (ByteBuffer) key.attachment();
buffer.clear();
//没有读到内容则关闭
if(sc.read(buffer)==-1){
sc.close();
}else{
//将buffer转成读状态
buffer.flip();
//将buffer中接收到的值按localCharset格式编码后保存到receivedString
String receivedString = Charset.forName(localCharset).newDecoder().decode(buffer).toString();
System.out.println("received from client: " + receivedString);
//返回数据给客户端
String sendString = "received data: " + receivedString;
buffer = ByteBuffer.wrap(sendString.getBytes(localCharset));
sc.write(buffer);
//关闭socket
sc.close();
}
}
}
}