package com.dragon;

public class Header {
	private byte type;      //文件類(lèi)型
	private long length;      //文件長(zhǎng)度
	
	public Header(byte type, long length) {
		super();
		this.type = type;
		this.length = length;
	}

	public byte getType() {
		return this.type;
	}
	
	public long getLength() {
		return this.length;
	}
}

package com.dragon;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.Socket;

/**
 * 模擬文件傳輸協(xié)議：
 * 協(xié)議包含一個(gè)頭部和一個(gè)數(shù)據(jù)部分。
 * 頭部為 9 字節(jié)，其余為數(shù)據(jù)部分。
 * 規(guī)定頭部包含：文件的類(lèi)型、文件數(shù)據(jù)的總長(zhǎng)度信息。
 * */
public class FileTransfer {
	private byte[] header = new byte[9];   //協(xié)議的頭部為9字節(jié)，第一個(gè)字節(jié)為文件類(lèi)型，后面8個(gè)字節(jié)為文件的字節(jié)長(zhǎng)度。
	
	/**
	 *@param src source folder 
	 * @throws IOException 
	 * @throws FileNotFoundException 
	 * */
	public void transfer(Socket client, String src) throws FileNotFoundException, IOException {
		File srcFile = new File(src);
		File[] files = srcFile.listFiles(f->f.isFile());
		//獲取輸出流
		BufferedOutputStream bos = new BufferedOutputStream(client.getOutputStream());
		for (File file : files) {
			try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file))){
				 //將文件寫(xiě)入流中
				String filename = file.getName();
				System.out.println(filename);
				//獲取文件的擴(kuò)展名
				String type = filename.substring(filename.lastIndexOf(".")+1);
				long len = file.length();
				//使用一個(gè)對(duì)象來(lái)保存文件的類(lèi)型和長(zhǎng)度信息，操作方便。
				Header h = new Header(this.getType(type), len);
				header = this.getHeader(h);
				
				//將文件基本信息作為頭部寫(xiě)入流中
				bos.write(header, 0, header.length);
				//將文件數(shù)據(jù)作為數(shù)據(jù)部分寫(xiě)入流中
				int hasRead = 0;
				byte[] b = new byte[1024];
				while ((hasRead = bis.read(b)) != -1) {
					bos.write(b, 0, hasRead);
				}
				bos.flush();   //強(qiáng)制刷新，否則會(huì)出錯(cuò)！
			}
		}
	}
	
	private byte[] getHeader(Header h) {
		byte[] header = new byte[9];
		byte t = h.getType();  
		long v = h.getLength();
		header[0] = t;                  //版本號(hào)
		header[1] = (byte)(v >>> 56);   //長(zhǎng)度
		header[2] = (byte)(v >>> 48);
		header[3] = (byte)(v >>> 40);
		header[4] = (byte)(v >>> 32);
		header[5] = (byte)(v >>> 24);
		header[6] = (byte)(v >>> 16);
		header[7] = (byte)(v >>>  8);
		header[8] = (byte)(v >>>  0);
		return header;
	}
	
	/**
	 * 使用 0-127 作為類(lèi)型的代號(hào)
	 * */
	private byte getType(String type) {
		byte t = 0;
		switch (type.toLowerCase()) {
		case "txt": t = 0; break;
		case "png": t=1; break;
		case "jpg": t=2; break;
		case "jpeg": t=3; break;
		case "avi": t=4; break;
		}
		return t;
	}
}

package com.dragon;

import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;

//類(lèi)型使用代號(hào)：固定長(zhǎng)度
//文件長(zhǎng)度：long->byte 固定長(zhǎng)度
public class Test {
	public static void main(String[] args) throws UnknownHostException, IOException {
		FileTransfer fileTransfer = new FileTransfer();
		try (Socket client = new Socket("127.0.0.1", 8000)) {
			fileTransfer.transfer(client, "D:/DBC/src");
		}
	}
}

package com.dragon;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.util.UUID;

/**
 * 接受客戶(hù)端傳過(guò)來(lái)的文件數(shù)據(jù)，并將其還原為文件。
 * */
public class FileResolve {
	private byte[] header = new byte[9];  
	
	/**
	 * @param des 輸出文件的目錄
	 * */
	public void fileResolve(Socket client, String des) throws IOException {
		BufferedInputStream bis = new BufferedInputStream(client.getInputStream());
		File desFile = new File(des);
		if (!desFile.exists()) {
			if (!desFile.mkdirs()) {
				throw new FileNotFoundException("無(wú)法創(chuàng)建輸出路徑");
			}
		}
		
		while (true) {	
			//先讀取文件的頭部信息
			int exit = bis.read(header, 0, header.length);
			
			//當(dāng)最后一個(gè)文件發(fā)送完，客戶(hù)端會(huì)停止，服務(wù)器端讀取完數(shù)據(jù)后，就應(yīng)該關(guān)閉了，
			//否則就會(huì)造成死循環(huán)，并且會(huì)批量產(chǎn)生最后一個(gè)文件，但是沒(méi)有任何數(shù)據(jù)。
			if (exit == -1) {
				System.out.println("文件上傳結(jié)束！");
				break;   
			}
			
			String type = this.getType(header[0]);
			String filename  = UUID.randomUUID().toString()+"."+type;
			System.out.println(filename);
			//獲取文件的長(zhǎng)度
			long len = this.getLength(header);
			long count = 0L;
			try (BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(new File(des, filename)))){
				int hasRead = 0;
				byte[] b = new byte[1024];
				while (count < len && (hasRead = bis.read(b)) != -1) {
					bos.write(b, 0, hasRead);
					count += (long)hasRead;
					/**
					 * 當(dāng)文件最后一部分不足1024時(shí)，直接讀取此部分，然后結(jié)束。
					 * 文件已經(jīng)讀取完成了。
					 * */
					int last = (int)(len-count);
					if (last < 1024 && last > 0) {
						//這里不考慮網(wǎng)絡(luò)原因造成的無(wú)法讀取準(zhǔn)確的字節(jié)數(shù)，暫且認(rèn)為網(wǎng)絡(luò)是正常的。
						byte[] lastData = new byte[last];
						bis.read(lastData);
						bos.write(lastData, 0, last);
						count += (long)last;
					}
				}
			}
		}
	}
	
	/**
	 * 使用 0-127 作為類(lèi)型的代號(hào)
	 * */
	private String getType(int type) {
		String t = "";
		switch (type) {
		case 0: t = "txt"; break;
		case 1: t = "png"; break;
		case 2: t = "jpg"; break;
		case 3: t = "jpeg"; break;
		case 4: t = "avi"; break;
		}
		return t;
	}
	
	private long getLength(byte[] h) {
		return (((long)h[1] << 56) +
                ((long)(h[2] & 255) << 48) +
                ((long)(h[3] & 255) << 40) +
                ((long)(h[4] & 255) << 32) +
                ((long)(h[5] & 255) << 24) +
                ((h[6] & 255) << 16) +
                ((h[7] & 255) <<  8) +
                ((h[8] & 255) <<  0));
	}
}

if (exit == -1) {
	System.out.println("文件上傳結(jié)束！");
	break;   
}

package com.dragon;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class Test {
	public static void main(String[] args) throws IOException {
		try (ServerSocket server = new ServerSocket(8000)){
			Socket client = server.accept();
			FileResolve fileResolve = new FileResolve();
			fileResolve.fileResolve(client, "D:/DBC/des");
		}	
	}
}