Java使用NIO优化IO实现文件上传下载功能

我来为您讲解一下“Java使用NIO优化IO实现文件上传下载功能”的完整攻略。

概述

Java NIO library 是Java语言提供的一种基于缓冲区、非阻塞的IO，使得Java应用程序能够快速轻便地处理并发客户端请求。使用Java NIO实现文件上传下载功能的好处是可以大大提高系统的吞吐量、降低系统的IO延迟，而且还能避免阻塞线程，提高服务器的并发能力。

Java NIO

Java NIO的核心概念包括通道（Channel）、缓冲区（Buffer）、选择器（Selector）和文件锁（FileLock）。其中，通道负责连接数据源，缓冲区负责存储数据，选择器负责监听通道的事件，文件锁提供了文件级别的共享锁。

文件上传实现

1. 创建文件上传的服务器端代码

import java.io.File;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;

public class NioServer {

    public static void main(String[] args) throws Exception {

        java.net.ServerSocket serverSocket = new java.net.ServerSocket(8888);

        System.out.println("NioServer has started");

        while (true) {

            SocketChannel socketChannel = SocketChannel.open();
            java.net.Socket socket = serverSocket.accept();
            System.out.println(socket.getInetAddress() + " is connected");

            ByteBuffer buffer = ByteBuffer.allocate(1024);
            while (socketChannel.read(buffer) != -1) {
                buffer.flip();
                Charset charset = Charset.forName("UTF-8");
                String message = new String(buffer.array(), 0, buffer.limit(), charset);
                System.out.println(message);
                buffer.clear();
            }

            String fileName = "C:\\tmp\\fileupload\\temp.log";
            FileChannel outChannel = new FileOutputStream(fileName).getChannel();
            ByteBuffer buffer1 = ByteBuffer.allocate(1024);

            long fileSize = socketChannel.read(buffer1);
            while (fileSize > 0) {
                buffer1.flip();
                outChannel.write(buffer1);
                buffer1.clear();
                fileSize = socketChannel.read(buffer1);
            }

            File file = new File(fileName);
            System.out.println(file.getName() + "has been saved at: " + file.getAbsolutePath());
            outChannel.close();
            socketChannel.close();
        }
    }
}

1. 创建文件上传的客户端代码

import java.io.File;
import java.io.FileInputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;

public class NioClient {

    public static void main(String[] args) throws Exception {

        String filePath = "C:\\tmp\\fileupload\\test.log";
        File file = new File(filePath);
        String fileName = file.getName();

        SocketChannel socketChannel = SocketChannel.open(new java.net.InetSocketAddress("localhost", 8888));

        Charset charset = Charset.forName("UTF-8");
        ByteBuffer buffer1 = ByteBuffer.allocate(1024);
        buffer1.put(fileName.getBytes(charset));
        buffer1.flip();
        socketChannel.write(buffer1);

        FileChannel inChannel = new FileInputStream(file).getChannel();
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        while (inChannel.read(buffer) != -1) {
            buffer.flip();
            socketChannel.write(buffer);
            buffer.clear();
        }

        inChannel.close();
        socketChannel.close();
    }
}

文件下载实现

1. 创建文件下载的服务器端代码

import java.io.File;
import java.io.FileInputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;

public class NioServer {

    public static void main(String[] args) throws Exception {

        java.net.ServerSocket serverSocket = new java.net.ServerSocket(8888);

        System.out.println("NioServer has started");

        while (true) {

            SocketChannel socketChannel = SocketChannel.open();
            java.net.Socket socket = serverSocket.accept();
            System.out.println(socket.getInetAddress() + " is connected");

            ByteBuffer buffer = ByteBuffer.allocate(1024);
            while (socketChannel.read(buffer) != -1) {
                buffer.flip();
                Charset charset = Charset.forName("UTF-8");
                String message = new String(buffer.array(), 0, buffer.limit(), charset);
                System.out.println(message);
                buffer.clear();
            }

            String filePath = "C:\\tmp\\filedownload\\" + message.trim();
            File file = new File(filePath);
            if (!file.exists()) {
                System.out.println("File does not exist");
            } else {
                FileChannel inChannel = new FileInputStream(file).getChannel();
                ByteBuffer buffer1 = ByteBuffer.allocate(1024);
                int bytesRead;
                while ((bytesRead = inChannel.read(buffer1)) != -1) {
                    buffer1.flip();
                    socketChannel.write(buffer1);
                    buffer1.clear();
                }

                System.out.println(file.getName() + "has been downloaded from: " + file.getAbsolutePath());
                inChannel.close();
            }

            socketChannel.close();
        }
    }
}

1. 创建文件下载的客户端代码

import java.io.File;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;

public class NioClient {

    public static void main(String[] args) throws Exception {

        String fileName = "test.log";
        SocketChannel socketChannel = SocketChannel.open(new java.net.InetSocketAddress("localhost", 8888));

        Charset charset = Charset.forName("UTF-8");
        ByteBuffer buffer1 = ByteBuffer.allocate(1024);
        buffer1.put(fileName.getBytes(charset));
        buffer1.flip();
        socketChannel.write(buffer1);

        String filePath = "C:\\tmp\\filedownload\\temp.log";
        FileChannel outChannel = new FileOutputStream(filePath).getChannel();
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        long fileSize = socketChannel.read(buffer);
        while (fileSize > 0) {
            buffer.flip();
            outChannel.write(buffer);
            buffer.clear();
            fileSize = socketChannel.read(buffer);
        }

        File file = new File(filePath);
        System.out.println(file.getName() + "has been saved at: " + file.getAbsolutePath());
        outChannel.close();
        socketChannel.close();
    }
}

以上就是Java使用NIO优化IO实现文件上传下载功能的完整攻略，希望对您有所帮助。