java 文件加密解密

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}    }