MD5加密Java工具類

import java.security.MessageDigest;
public class MD5 {
    //公鹽
    private static final String PUBLIC_SALT = "demo" ;
    //十六進制下數字到字符的映射數組

    private final static String[] hexDigits = {"0", "1", "2", "3", "4",

        "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};


/**
 * 用戶密碼加密，鹽值為 ：私鹽+公鹽
 * @param  password 密碼
 * @param  salt 私鹽
 * @return  MD5加密字符串
 */
public static String encryptPassword(String password,String salt){
    return encodeByMD5(PUBLIC_SALT+password+salt);
}

/**
 * md5加密算法
 * @param  originString
 * @return 
 */
private static String encodeByMD5(String originString){  
    if (originString != null){  
        try{  
            //創建具有指定算法名稱的信息摘要  
            MessageDigest md = MessageDigest.getInstance("MD5");  
            //使用指定的字節數組對摘要進行最后更新，然后完成摘要計算  
            byte[] results = md.digest(originString.getBytes());  
            //將得到的字節數組變成字符串返回  
            String resultString = byteArrayToHexString(results);  
            return resultString.toUpperCase();  
        } catch(Exception ex){  
            ex.printStackTrace();  
        }  
    }  
    return null;  
} 

/**  
 * 轉換字節數組為十六進制字符串 
 * @param     字節數組 
 * @return    十六進制字符串 
 */  
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();  
}  

/** 將一個字節轉化成十六進制形式的字符串     */  
private static String byteToHexString(byte b){  
    int n = b;  
    if (n < 0)  
        n = 256 + n;  
    int d1 = n / 16;  
    int d2 = n % 16;  
    return hexDigits[d1] + hexDigits[d2];  
}

}</pre>