/*
    *加密生成MD5
    */
     public static String MD5(string s)

        {

            char[] hexDigits = { '', '', '', '', '', '', '', '', '', '', 'a', 'b', 'c', 'd', 'e', 'f' };

            MD5 md5 = new MD5CryptoServiceProvider();

            byte[] inputBytes = System.Text.Encoding.Default.GetBytes(s);

            byte[] result = md5.ComputeHash(inputBytes);

            int j = result.Length;

            char[] str = new char[j * ];

            int k = ;

            for (int i = ; i < j; i++)

            {

                byte byte0 = result[i];

                str[k++] = hexDigits[byte0 >>  & 0xf];

                str[k++] = hexDigits[byte0 & 0xf];

            }

            return new String(str);

        } 

public final class DefaultPasswordEncoder {

    private static final char[] HEX_DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8',

                                                '9', 'a', 'b', 'c', 'd', 'e', 'f'};

    private final String encodingAlgorithm="MD5";

    private final String characterEncoding="UTF-8";

    /*
    *加密生成MD5
    */

    public String encode(final String password) {

        if (password == null) {

            return null;

        }

        try {

            MessageDigest messageDigest = MessageDigest

                .getInstance(this.encodingAlgorithm);

            if (StringUtils.hasText(this.characterEncoding)) {

                messageDigest.update(password.getBytes(this.characterEncoding));

            } else {

                messageDigest.update(password.getBytes());

            }

            final byte[] digest = messageDigest.digest();

            return getFormattedText(digest);

        } catch (final NoSuchAlgorithmException e) {

            throw new SecurityException(e);

        } catch (final UnsupportedEncodingException e) {

            throw new RuntimeException(e);

        }

    }

    /**

     * Takes the raw bytes from the digest and formats them correct.

     *

     * @param bytes the raw bytes from the digest.

     * @return the formatted bytes.

     */

    private String getFormattedText(final byte[] bytes) {

        final StringBuilder buf = new StringBuilder(bytes.length * 2);

        for (int j = 0; j < bytes.length; j++) {

            buf.append(HEX_DIGITS[(bytes[j] >> 4) & 0x0f]);

            buf.append(HEX_DIGITS[bytes[j] & 0x0f]);

        }

        return buf.toString();

    }

}