NIO的非阻塞模式
NIO完成核心的东西是一个选择器,Selector,选择器主要是将每一个传输数据的通道注册到选择器上,选择器作用是监控这些IO的状态(读,写,连接状态),然后用选择器监控通道的状况,等待所有的线程准备就绪时,选择器将任务分配到服务端一个或者多个线程上再去运行
NIO完成网络通信的三个核心
1.通道(Channel):负责连接
java.nio.channels.Channel 接口:
SelectChannel接口下有,SocketChannel,ServerSocketChannel,DatagramChannel
pipe.SinkChannel和PipeSourceChannel
2.缓冲区(Buffer):负责数据的存取
3.选择器(Selector):是SelectableChannel的多路复用器,用于监控SelectableChannel的IO状况
阻塞式IO代码
package com.nio02;
import org.junit.Test;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
public class TestBlockingNIO {
//客户端
@Test
public void client() throws IOException {
//1. 获取通道
SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
FileChannel inChannel = FileChannel.open(Paths.get("a.txt"), StandardOpenOption.READ);
//2. 分配指定大小的缓冲区
ByteBuffer buf = ByteBuffer.allocate(1024);
//3. 读取本地文件,并发送到服务端
while (inChannel.read(buf) != -1) {
buf.flip();
sChannel.write(buf);
buf.clear();
}
//4. 关闭通道
inChannel.close();
sChannel.close();
}
//服务端
@Test
public void server() throws IOException {
//1. 获取通道
ServerSocketChannel ssChannel = ServerSocketChannel.open();
FileChannel outChannel = FileChannel.open(Paths.get("a2.txt"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);
//2. 绑定连接
ssChannel.bind(new InetSocketAddress(9898));
//3. 获取客户端连接的通道
SocketChannel sChannel = ssChannel.accept();
//4. 分配指定大小的缓冲区
ByteBuffer buf = ByteBuffer.allocate(1024);
//5. 接受客户端的数据,并保存到本地
while (sChannel.read(buf)!= -1){
buf.flip();
outChannel.write(buf);
buf.clear();
}
//6. 关闭通道
sChannel.close();
outChannel.close();
ssChannel.close();
}
}
原本阻塞式IO需要shutdownOutput()
package com.nio02;
import org.junit.Test;
import scala.reflect.io.Path;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
public class TestBlockingNIO2 {
//服务端
@Test
public void server() throws IOException {
ServerSocketChannel ssChannel = ServerSocketChannel.open();
FileChannel outChannel = FileChannel.open(Paths.get("a.txt"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);
ssChannel.bind(new InetSocketAddress(9898));
SocketChannel sChannel = ssChannel.accept();
ByteBuffer buf = ByteBuffer.allocate(1024);
while (sChannel.read(buf)!= -1){
buf.flip();
outChannel.write(buf);
buf.clear();
}
//发送反馈给客户端
buf.put("服务端接受数据成功!".getBytes());
buf.flip();
sChannel.write(buf);
sChannel.close();
outChannel.close();
ssChannel.close();
}
//客户端
@Test
public void client() throws IOException {
SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
FileChannel inChannel = FileChannel.open(Paths.get("a.txt"),StandardOpenOption.READ);
ByteBuffer buf = ByteBuffer.allocate(1024);
while (inChannel.read(buf) != -1){
buf.flip();
sChannel.write(buf);
buf.clear();
}
sChannel.shutdownOutput();
//接受服务端的反馈
int len = 0;
while ((len = sChannel.read(buf))!= -1){
buf.flip();
System.out.println(new String(buf.array(),0,len));
buf.clear();
}
inChannel.close();
sChannel.close();
}
}
非阻塞式IO操作
//客户端
@Test
public void client() throws IOException{
//1. 获取通道
SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
//2. 切换非阻塞模式
sChannel.configureBlocking(false);
//3. 分配指定大小的缓冲区
ByteBuffer buf = ByteBuffer.allocate(1024);
//4. 发送数据给服务端
Scanner scan = new Scanner(System.in);
while(scan.hasNext()){
String str = scan.next();
buf.put((new Date().toString() + "\n" + str).getBytes());
buf.flip();
sChannel.write(buf);
buf.clear();
}
//5. 关闭通道
sChannel.close();
}
//服务端
@Test
public void server() throws IOException{
//1. 获取通道
ServerSocketChannel ssChannel = ServerSocketChannel.open();
//2. 切换非阻塞模式
ssChannel.configureBlocking(false);
//3. 绑定连接
ssChannel.bind(new InetSocketAddress(9898));
//4. 获取选择器
Selector selector = Selector.open();
//5. 将通道注册到选择器上, 并且指定“监听接收事件”
ssChannel.register(selector, SelectionKey.OP_ACCEPT);
//6. 轮询式的获取选择器上已经“准备就绪”的事件
while(selector.select() > 0){
//7. 获取当前选择器中所有注册的“选择键(已就绪的监听事件)”
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while(it.hasNext()){
//8. 获取准备“就绪”的是事件
SelectionKey sk = it.next();
//9. 判断具体是什么事件准备就绪
if(sk.isAcceptable()){
//10. 若“接收就绪”，获取客户端连接
SocketChannel sChannel = ssChannel.accept();
//11. 切换非阻塞模式
sChannel.configureBlocking(false);
//12. 将该通道注册到选择器上
sChannel.register(selector, SelectionKey.OP_READ);
}else if(sk.isReadable()){
//13. 获取当前选择器上“读就绪”状态的通道
SocketChannel sChannel = (SocketChannel) sk.channel();
//14. 读取数据
ByteBuffer buf = ByteBuffer.allocate(1024);
int len = 0;
while((len = sChannel.read(buf)) > 0 ){
buf.flip();
System.out.println(new String(buf.array(), 0, len));
buf.clear();
}
}
//15. 取消选择键 SelectionKey
it.remove();
}
}
}
