java 文件加密解密

﹏ヽ暗。殇╰゛Y 2022-09-17 15:17 218阅读 0赞

import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.io.RandomAccessFile;
    /**
     * 文件加密、解密
     * @author admin_Hzw
     *
     */
    public class FileEncryptAndDecrypt {
    	/**
    	 * 文件file进行加密
    	 * @param fileUrl 文件路径
    	 * @param key 密码
    	 * @throws Exception
    	 */
    	public static void encrypt(String fileUrl, String key) throws Exception {
    		File file = new File(fileUrl);
    		String path = file.getPath();
    		if(!file.exists()){
    			return;
    		}
    		int index = path.lastIndexOf("\\");
    		String destFile = path.substring(0, index)+"\\"+"abc";
    		File dest = new File(destFile);
    		InputStream in = new FileInputStream(fileUrl);
    		OutputStream out = new FileOutputStream(destFile);
    		byte[] buffer = new byte[1024];
    		int r;
    		byte[] buffer2=new byte[1024];
    		while (( r= in.read(buffer)) > 0) {
    			for(int i=0;i<r;i++)
    			{
    				byte b=buffer[i];
    				buffer2[i]=b==255?0:++b;
    			}
    			out.write(buffer2, 0, r);
    			out.flush();
    		}
    		in.close();
    		out.close();
    		file.delete();
    		dest.renameTo(new File(fileUrl));
    		appendMethodA(fileUrl, key);
    		System.out.println("加密成功");
    	}
    
    	/**
    	 * 
    	 * @param fileName
    	 * @param content 密钥
    	 */
    	public static void appendMethodA(String fileName, String content) {
    		try {
    			// 打开一个随机访问文件流，按读写方式
    			RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");
    			// 文件长度，字节数
    			long fileLength = randomFile.length();
    			//将写文件指针移到文件尾。
    			randomFile.seek(fileLength);
    			randomFile.writeBytes(content);
    			randomFile.close();
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    	}
    	/**
    	 * 解密
    	 * @param fileUrl 源文件
    	 * @param tempUrl 临时文件
    	 * @param ketLength 密码长度
    	 * @return
    	 * @throws Exception
    	 */
    	public static String decrypt(String fileUrl, String tempUrl, int keyLength) throws Exception{
    		File file = new File(fileUrl);
    		if (!file.exists()) {
    			return null;
    		}
    		File dest = new File(tempUrl);
    		if (!dest.getParentFile().exists()) {
    			dest.getParentFile().mkdirs();
    		}
    
    		InputStream is = new FileInputStream(fileUrl);
    		OutputStream out = new FileOutputStream(tempUrl);
    
    		byte[] buffer = new byte[1024];
    		byte[] buffer2=new byte[1024];
    		byte bMax=(byte)255;
    		long size = file.length() - keyLength;
    		int mod = (int) (size%1024);
    		int div = (int) (size>>10);
    		int count = mod==0?div:(div+1);
    		int k = 1, r;
    		while ((k <= count && ( r = is.read(buffer)) > 0)) {
    			if(mod != 0 && k==count) {
    				r =  mod;
    			}
    
    			for(int i = 0;i < r;i++)
    			{
    				byte b=buffer[i];
    				buffer2[i]=b==0?bMax:--b;
    			}
    			out.write(buffer2, 0, r);
    			k++;
    		}
    		out.close();
    		is.close();
    		return tempUrl;
    	}
    
    	/**
    	 * 判断文件是否加密
    	 * @param fileName
    	 * @return
    	 */
    	public static String readFileLastByte(String fileName, int keyLength) {
    		File file = new File(fileName);
    		if(!file.exists())return null;
    		StringBuffer str = new StringBuffer();
    		try {
    			// 打开一个随机访问文件流，按读写方式
    			RandomAccessFile randomFile = new RandomAccessFile(fileName, "r");
    			// 文件长度，字节数
    			long fileLength = randomFile.length();
    			//将写文件指针移到文件尾。
    			for(int i = keyLength ; i>=1 ; i--){
    				randomFile.seek(fileLength-i);
    				str.append((char)randomFile.read());
    			}
    			randomFile.close();
    			return str.toString();
    		} catch (IOException e) {
    			e.printStackTrace();  
    		}  
    		return null;
    	}
    	public static void main(String[] args) throws Exception {
    		String path = "D:/temp";  
    		encrypt(path+"/ipconfig.txt","mimimamamima99188");  //加密  
    		decrypt(path+"/ipconfig.txt","D:/temp/decrypt.txt","mimimamamima99188".length());//解密
    	}    
    }