base64

	// 将 s 进行 BASE64 编码
	public static String getBASE64(String s) {
		if (s == null)
			return null;
		return (new sun.misc.BASE64Encoder()).encode(s.getBytes());
	}

	// 将 BASE64 编码的字符串 s 进行解码
	public static String getFromBASE64(String s) {
		if (s == null)
			return null;
		BASE64Decoder decoder = new BASE64Decoder();
		try {
			byte[] b = decoder.decodeBuffer(s);
			return new String(b);
		} catch (Exception e) {
			return null;
		}
	}

http://www.coolcode.cn/show-203-1.html   byte->string  string->byte

public class base64 {
 private static char[] base64EncodeChars = new char[] { 'A', 'B', 'C', 'D',
   'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',
   'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
   'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q',
   'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3',
   '4', '5', '6', '7', '8', '9', '+', '/' };

 private static byte[] base64DecodeChars = new byte[] { -1, -1, -1, -1, -1,
   -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
   -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
   -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59,
   60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
   10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1,
   -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,
   38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,
   -1, -1 };

 public static String dwBase64Encode(byte[] data, int iLen) {
  StringBuffer sb = new StringBuffer();
  int len = data.length < iLen ? data.length : iLen;
  int i = 0;
  int b1, b2, b3;
  while (i < len) {
   b1 = data[i++] & 0xff;
   if (i == len) {
    sb.append(base64EncodeChars[b1 >>> 2]);
    sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
    sb.append("==");
    break;
   }
   b2 = data[i++] & 0xff;
   if (i == len) {
    sb.append(base64EncodeChars[b1 >>> 2]);
    sb.append(base64EncodeChars[((b1 & 0x03) << 4)
      | ((b2 & 0xf0) >>> 4)]);
    sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
    sb.append("=");
    break;
   }
   b3 = data[i++] & 0xff;
   sb.append(base64EncodeChars[b1 >>> 2]);
   sb.append(base64EncodeChars[((b1 & 0x03) << 4)
     | ((b2 & 0xf0) >>> 4)]);
   sb.append(base64EncodeChars[((b2 & 0x0f) << 2)
     | ((b3 & 0xc0) >>> 6)]);
   sb.append(base64EncodeChars[b3 & 0x3f]);
  }
  return sb.toString();
  
 }

 public static byte[] dwBase64Decode(String str)
   throws UnsupportedEncodingException {
  StringBuffer sb = new StringBuffer();
  byte[] data = str.getBytes("US-ASCII");
  int len = data.length;
  int i = 0;
  int b1, b2, b3, b4;
  while (i < len) {
   /* b1 */
   do {
    b1 = base64DecodeChars[data[i++]];
   } while (i < len && b1 == -1);
   if (b1 == -1)
    break;
   /* b2 */
   do {
    b2 = base64DecodeChars[data[i++]];
   } while (i < len && b2 == -1);
   if (b2 == -1)
    break;
   sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));
   /* b3 */
   do {
    b3 = data[i++];
    if (b3 == 61)
     return sb.toString().getBytes("ISO-8859-1");
    b3 = base64DecodeChars[b3];
   } while (i < len && b3 == -1);
   if (b3 == -1)
    break;
   sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));
   /* b4 */
   do {
    b4 = data[i++];
    if (b4 == 61)
     return sb.toString().getBytes("ISO-8859-1");
    b4 = base64DecodeChars[b4];
   } while (i < len && b4 == -1);
   if (b4 == -1)
    break;
   sb.append((char) (((b3 & 0x03) << 6) | b4));
  }
  return sb.toString().getBytes("ISO-8859-1");
 }
}