java 实现文件内容的加密和解密

转载：http://xiaoxiaokuang.iteye.com/blog/1440031

 package com.umapp.test;

 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.security.Key;
 import java.security.SecureRandom;

 import javax.crypto.Cipher;
 import javax.crypto.CipherInputStream;
 import javax.crypto.CipherOutputStream;
 import javax.crypto.KeyGenerator;

 public class TestDES {
   Key key;
   public TestDES(String str) {
     getKey(str);//生成密匙
   }
   /**
   * 根据参数生成KEY
   */
   public void getKey(String strKey) {
     try {
         KeyGenerator _generator = KeyGenerator.getInstance("DES");
         _generator.init(new SecureRandom(strKey.getBytes()));
         this.key = _generator.generateKey();
         _generator = null;
     } catch (Exception e) {
         throw new RuntimeException("Error initializing SqlMap class. Cause: " + e);
     }
   }

   /**
   * 文件file进行加密并保存目标文件destFile中
   *
   * @param file   要加密的文件 如c:/test/srcFile.txt
   * @param destFile 加密后存放的文件名 如c:/加密后文件.txt
   */
   public void encrypt(String file, String destFile) throws Exception {
     Cipher cipher = Cipher.getInstance("DES");
     // cipher.init(Cipher.ENCRYPT_MODE, getKey());
     cipher.init(Cipher.ENCRYPT_MODE, this.key);
     InputStream is = new FileInputStream(file);
     OutputStream out = new FileOutputStream(destFile);
     CipherInputStream cis = new CipherInputStream(is, cipher);
     byte[] buffer = new byte[1024];
     int r;
     while ((r = cis.read(buffer)) > 0) {
         out.write(buffer, 0, r);
     }
     cis.close();
     is.close();
     out.close();
   }
   /**
   * 文件采用DES算法解密文件
   *
   * @param file 已加密的文件 如c:/加密后文件.txt
   *         * @param destFile
   *         解密后存放的文件名 如c:/ test/解密后文件.txt
   */
   public void decrypt(String file, String dest) throws Exception {
     Cipher cipher = Cipher.getInstance("DES");
     cipher.init(Cipher.DECRYPT_MODE, this.key);
     InputStream is = new FileInputStream(file);
     OutputStream out = new FileOutputStream(dest);
     CipherOutputStream cos = new CipherOutputStream(out, cipher);
     byte[] buffer = new byte[1024];
     int r;
     while ((r = is.read(buffer)) >= 0) {
         System.out.println();
         cos.write(buffer, 0, r);
     }
     cos.close();
     out.close();
     is.close();
   }
   public static void main(String[] args) throws Exception {
     TestDES td = new TestDES("aaa");
     td.encrypt("e:/r.txt", "e:/r解密.txt"); //加密
     td.decrypt("e:/r解密.txt", "e:/r1.txt"); //解密

   }
 }