Netty之网络编程阻塞篇

1.什么是阻塞？

• 阻塞模式下，相关方法都会导致线程暂停
  • ServerSocketChannel.accept 会在没有连接建立时让线程暂停
  • SocketChannel.read 会在通道中没有数据可读时让线程暂停
  • 阻塞的表现其实就是线程暂停了，暂停期间不会占用 cpu，但线程相当于闲置。

2.通过设置serverSocketChannel.configureBlocking(false)设置成非阻塞模式

package netty.io;

import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.ArrayList;
import java.util.List;
@Slf4j
public class ZuSeServer {
    public static void main(String[] args) throws IOException {
        //0Bytebuffer
        ByteBuffer byteBuffer=ByteBuffer.allocate(16);
        //1创建了服务器
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.configureBlocking(false);//设置成非阻塞模式
        //2绑定端口
        serverSocketChannel.bind(new InetSocketAddress(8080));
        //3连接的集合 存放channel
        List<SocketChannel> channels=new ArrayList<>();
        while(true){
            //4 accept建立于客户端连接
            log.info("connetcing...");
//            System.out.println("connecting...");
            SocketChannel sc = serverSocketChannel.accept();//也是阻塞
            sc.configureBlocking(false);
            log.info("connected...");
            channels.add(sc);
            for(SocketChannel channel:channels){
                //5接受客户端发送的数据
                log.info("before read",channel);
                channel.read(byteBuffer);//也是阻塞
                byteBuffer.flip();
//                ByteBufferUtil.debugAll(byteBuffer);
                byteBuffer.clear();
                log.info("after read");
            }
        }

    }
}