工具类--MD5Utils

public class MD5Utils {

    private static final String[] HEX_DIGITS = { "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

    private static String byteArrayToHexString(byte b[]) {
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++) {
         resultSb.append(byteToHexString(b[i]));
      }

        return resultSb.toString();
    }

    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0) {
         n += 256;
      }
        int d1 = n / 16;
        int d2 = n % 16;
        return HEX_DIGITS[d1] + HEX_DIGITS[d2];
    }

    /**
     * 字符串MD5加密
     * @param str
     * @return
     */
    public static String encode(String str) throws Exception {
        if (StringUtils.hasText(str)) {
            return DigestUtils.md5DigestAsHex(str.getBytes());
        }
        return null;
    }

    public static String md5Encode(String origin, String charsetname) {
        String resultString = null;
        try {
            resultString = new String(origin);
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (charsetname == null || "".equals(charsetname)) {
            resultString = byteArrayToHexString(md.digest(resultString
                  .getBytes()));
         } else {
            resultString = byteArrayToHexString(md.digest(resultString
                  .getBytes(charsetname)));
         }
        } catch (Exception exception) {
        }
        return resultString;
    }

}