网络编程之NIO

Posted 2020-11-24 itbac

一、Buffer缓冲区

package com.itbac.net.NIO.BIO;

import java.nio.ByteBuffer;

/**
 * Buffer缓冲区
 */
public class BufferDemo {
    public static void main(String[] args) {
        //构建一个byte 字节缓冲区，容量是4
        // allocate分配内存（在堆中）堆中内存要复制到堆外才能用于网络通信,因为堆中有GC管理
        // allocateDirect 分配内存（在堆外）,减少一次内存复制操作，提高性能，但是要自己回收内存
        ByteBuffer byteBuffer = ByteBuffer.allocate(4);
        System.out.println(String.format("初始化：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
        //写入3字节的数据
        byteBuffer.put((byte) 1);
        byteBuffer.put((byte) 2);
        byteBuffer.put((byte) 3);
        System.out.println(String.format("写入3字节后：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
        System.out.println("开始读取——");
        byteBuffer.flip();
        System.out.println(String.format("切换成读模式：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
        byte a = byteBuffer.get();
        System.out.println("读第1个："+a);
        System.out.println(String.format("读取1字节后：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
        byte b = byteBuffer.get();
        System.out.println("读第2个："+b);
        System.out.println(String.format("读取2字节后：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
        /**
         * 继续写入3字节，此时读模式下，limit=3，position=2，继续写入只能写入一条数据，再多就会溢出。java.nio.BufferOverflowException
         * clear()方法清除整个缓存去。 compact()方法仅清除已阅读的数据。==> 两个方法都会转为写入模式。
         */
        byteBuffer.compact();
        System.out.println(String.format("compact()后：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
        byteBuffer.put((byte) 4);
        byteBuffer.put((byte) 5);
        byteBuffer.put((byte) 6);
        System.out.println(String.format("最终的情况：capacity容量：%s,position位置：%s,limit限制：%s",
                byteBuffer.capacity(),
                byteBuffer.position(),
                byteBuffer.limit()));
//        byteBuffer.rewind(); 重置position为0
//        byteBuffer.mark(); 标记position的位置
//        byteBuffer.reset(); 重置position为上次 mark()标记的位置



    }
}

二、Channel通道

客户端

package com.itbac.net.NIO.BIO;


import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
import java.util.Scanner;
//客户端
public class NIOClient {
    public static void main(String[] args) throws IOException {
        //创建客户端通道
        SocketChannel socketChannel = SocketChannel.open();
        //设置非阻塞
        socketChannel.configureBlocking(false);
        socketChannel.connect(new InetSocketAddress("127.0.0.1", 8080));
        while (!socketChannel.finishConnect()) {
            //没连接上，则让出CPU ,一直等待
            Thread.yield();
        }
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入：");
        //发送内容
        String msg = scanner.nextLine();
        //包装要发出的数据
        ByteBuffer byteBuffer = ByteBuffer.wrap(msg.getBytes());
        while (byteBuffer.hasRemaining()) {
            //如果Buffer缓冲区有剩余，循环写入通道中。
            socketChannel.write(byteBuffer);
        }

        //读取响应
        System.out.println("收到服务端响应：");
        //开辟接收数据内存空间,堆内
        ByteBuffer requestBuffer = ByteBuffer.allocate(1024);
        //通道开启状态 & 从通道读数据，写入到 buffer缓存区
        while (socketChannel.isOpen()&& socketChannel.read(requestBuffer) !=-1) {
        //长连接情况下，需要手动判断数据有没有读取结束。
            if (requestBuffer.position()==requestBuffer.limit()) {
                //buffer缓冲区，写入模式切换成读取模式
                requestBuffer.flip();
                byte[] content = new byte[requestBuffer.limit()];
               requestBuffer.get(content);
                System.out.println(new String(content));
                //清空已读，转成写模式
                requestBuffer.compact();
            }
        }
        //大于0 ，有写入的数据
        if (requestBuffer.position()>0) {
            //buffer缓冲区，写入模式切换成读取模式
            requestBuffer.flip();
            byte[] content = new byte[requestBuffer.limit()];
            requestBuffer.get(content);
            System.out.println(new String(content));
            //清空已读，转成写模式
            requestBuffer.compact();
        }
        //关闭键盘录入
        scanner.close();
        //关闭通道
        socketChannel.close();



    }
}

服务端

package com.itbac.net.NIO.BIO;

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;

public class Nioserver {
    public static void main(String[] args) throws IOException {
        //创建网络服务端
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        //设置非阻塞IO
        serverSocketChannel.configureBlocking(false);
        //获取服务端套接字
        ServerSocket serverSocket = serverSocketChannel.socket();
        //绑定地址
        serverSocket.bind(new InetSocketAddress("127.0.0.1",8080));

        while (true) {
            SocketChannel socketChannel = serverSocketChannel.accept(); // 获取新tcp连接通道
            // tcp请求 读取/响应
            if (socketChannel != null) {
                System.out.println("收到新连接 : " + socketChannel.getRemoteAddress());
                socketChannel.configureBlocking(false); // 默认是阻塞的,一定要设置为非阻塞
                try {
                    ByteBuffer requestBuffer = ByteBuffer.allocate(1024);
                    while (socketChannel.isOpen() && socketChannel.read(requestBuffer) != -1) {
                        // 长连接情况下,需要手动判断数据有没有读取结束 (此处做一个简单的判断: 超过0字节就认为请求结束了)
                        if (requestBuffer.position() > 0) {
                            break;
                        }
                    }
                    if(requestBuffer.position() == 0) {
                        continue; // 如果没数据了, 则不继续后面的处理
                    }
                    requestBuffer.flip();
                    byte[] content = new byte[requestBuffer.limit()];
                    requestBuffer.get(content);
                    System.out.println(new String(content));
                    System.out.println("收到数据,来自："+ socketChannel.getRemoteAddress());

                    // 响应结果 200
                    String response = "HTTP/1.1 200 OK
" +
                            "Content-Length: 11

" +
                            "Hello World";
                    ByteBuffer buffer = ByteBuffer.wrap(response.getBytes());
                    while (buffer.hasRemaining()) {
                        socketChannel.write(buffer);// 非阻塞
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
// 用到了非阻塞的API, 在设计上,和BIO可以有很大的不同.继续改进
    }
}