import java.security.*;

         import javax.crypto.Cipher;

         import javax.crypto.SecretKey;

         import javax.crypto.SecretKeyFactory;

         import javax.crypto.spec.DESKeySpec;

         /**

          * 字符串工具集合

          * @author Liudong

          */

         public class StringUtils {

           PRivate static final String PASSWord_CRYPT_KEY = "__jDlog_";

         private final static String DES = "DES";

         /**

          * 加密

          * @param src 數據源

          * @param key 密鑰，長度必須是8的倍數

          * @return  返回加密后的數據

          * @throws Exception

          */

         public static byte[] encrypt(byte[] src, byte[] key)throws Exception {

                 //DES算法要求有一個可信任的隨機數源

                 SecureRandom sr = new SecureRandom();

                 // 從原始密匙數據創建DESKeySpec對象

                 DESKeySpec dks = new DESKeySpec(key);

                 // 創建一個密匙工廠，然后用它把DESKeySpec轉換成

                 // 一個SecretKey對象

                 SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);

                 SecretKey securekey = keyFactory.generateSecret(dks);

                 // Cipher對象實際完成加密操作

                 Cipher cipher = Cipher.getInstance(DES);

                 // 用密匙初始化Cipher對象

                 cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);

                 // 現在，獲取數據并加密

                 // 正式執行加密操作

                 return cipher.doFinal(src);

              }

              /**

              * 解密

              * @param src 數據源

              * @param key 密鑰，長度必須是8的倍數

              * @return   返回解密后的原始數據

              * @throws Exception

              */

              public static byte[] decrypt(byte[] src, byte[] key)throws Exception {

                 // DES算法要求有一個可信任的隨機數源

                 SecureRandom sr = new SecureRandom();

                 // 從原始密匙數據創建一個DESKeySpec對象

                 DESKeySpec dks = new DESKeySpec(key);

                 // 創建一個密匙工廠，然后用它把DESKeySpec對象轉換成

                 // 一個SecretKey對象

                 SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);

                 SecretKey securekey = keyFactory.generateSecret(dks);

                 // Cipher對象實際完成解密操作

                 Cipher cipher = Cipher.getInstance(DES);

                 // 用密匙初始化Cipher對象

                 cipher.init(Cipher.DECRYPT_MODE, securekey, sr);

                 // 現在，獲取數據并解密

                 // 正式執行解密操作

                 return cipher.doFinal(src);

              }

           /**

            * 密碼解密

            * @param data

            * @return

            * @throws Exception

            */

           public final static String decrypt(String data){

              try {

               return new String(decrypt(hex2byte(data.getBytes()),

                  PASSWORD_CRYPT_KEY.getBytes()));

             }catch(Exception e) {

             }

             return null;

           }

           /**

            * 密碼加密

            * @param password

            * @return

            * @throws Exception

            */

           public final static String encrypt(String password){

             try {

               return byte2hex(encrypt(password.getBytes(),PASSWORD_CRYPT_KEY.getBytes()));
             }catch(Exception e) {

             }

             return null;

           }

         /**

          * 二行制轉字符串

          * @param b

          * @return

          */

           public static String byte2hex(byte[] b) {

                 String hs = "";

                 String stmp = "";

                 for (int n = 0; n < b.length; n++) {

                     stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));

                     if (stmp.length() == 1)

                         hs = hs + "0" + stmp;

                     else

                         hs = hs + stmp;

                 }

                 return hs.toUpperCase();

            }

           public static byte[] hex2byte(byte[] b) {

             if((b.length%2)!=0)

                throw new IllegalArgumentException("長度不是偶數");

                 byte[] b2 = new byte[b.length/2];

                 for (int n = 0; n < b.length; n+=2) {

                   String item = new String(b,n,2);

                   b2[n/2] = (byte)Integer.parseInt(item,16);

                 }

             return b2;
http://blog.csdn.net/s449201708/archive/2009/03/24/4020757.aspx