MD5加密

写法一：

/**
 * md5加密
 * @param origin 明文
 * @param charsetname 格式“utf-8”
 * @return
 */
public static String MD5Encode(String origin, String charsetname) {
    String resultString = null;
    try {
        resultString = new String(origin);
        MessageDigest md = MessageDigest.getInstance("MD5");
        md.update(origin.getBytes("UTF-8"));
        BigInteger hash = new BigInteger(1, md.digest());
        resultString = hash.toString(16);
        if ((resultString.length() % 2) != 0) {
            resultString = "0" + resultString;
        }
    } catch (Exception exception) {
    }
    return resultString;
}

写法二：

private static final String MD5_SUFFIX = "_www.baidu.com_"; 

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

/** 
 * 字符加密 
 * @param str 明文 
 * @return 返回加了后缀的加密字符 
 */
public static String encryptByMD5(String str) {  
    try {  
        if (str == null || str.length() < 1 || "0".equals(str))  
            str = "0";  
        String tmp = md5(str + MD5_SUFFIX, "UTF-8");  
       if (null != tmp) {  
           return replace(tmp, ":", "", -1).toLowerCase();  
       }  
    } catch (NoSuchAlgorithmException e) {  
        e.printStackTrace();  
    } catch (UnsupportedEncodingException e) {  
        e.printStackTrace();  
    }
    return "";  
}  

/** 
 * md5加密方法，不可逆转 
 * @param str 明文 
 * @param charset 字符编码 
 * @return 
 * @throws NoSuchAlgorithmException 
 * @throws UnsupportedEncodingException 
 */  
public static String md5(String str, String charset)   
        throws NoSuchAlgorithmException, UnsupportedEncodingException {  
    byte[] tmpInput = null;  
    if (null != str) {  
        if (null != charset) {  
            tmpInput = str.getBytes(charset);  
        } else {  
            tmpInput = str.getBytes();  
        }  
    } else {  
        return null;  
    }  
    MessageDigest alg = MessageDigest.getInstance("MD5"); // or "SHA-1"  
    alg.update(tmpInput);  
    return byte1hex(alg.digest());  
}

public static String replace(String text, String repl, String with, int max) {  
    if (isEmpty(text) || isEmpty(repl) || with == null || max == 0) {  
        return text;  
    }  
    int start = 0;  
    int end = text.indexOf(repl, start);  
    if (end == -1) {  
        return text;  
    }  
    int replLength = repl.length();  
    int increase = with.length() - replLength;  
    increase = (increase < 0 ? 0 : increase);  
    increase *= (max < 0 ? 16 : (max > 64 ? 64 : max));  
    StringBuffer buf = new StringBuffer(text.length() + increase);  
    while (end != -1) {  
        buf.append(text.substring(start, end)).append(with);  
        start = end + replLength;  
        if (--max == 0) {  
            break;  
        }  
        end = text.indexOf(repl, start);  
    }  
    buf.append(text.substring(start));  
    return buf.toString();  
}  

/** 
     * 字节码转换成16进制字符串 
     * @param inputByte 
     * @return 
     */ 
    public static String byte1hex(byte[] inputByte) {  
        if (null == inputByte) {  
            return null;  
        }  
        String resultStr = "";  
        String tmpStr = "";  
        for (int n = 0; n < inputByte.length; n++) {  
            tmpStr = (Integer.toHexString(inputByte[n] & 0XFF));  
            if (tmpStr.length() == 1)  
                resultStr = resultStr + "0" + tmpStr;  
            else  
                resultStr = resultStr + tmpStr;  
            if (n < inputByte.length - 1)  
                resultStr = resultStr + "";  
        }  
        return resultStr.toLowerCase();  
    }