MD5加密Java工具类

原文：http://www.open-open.com/code/view/1421764946296

import java.security.MessageDigest;
public class MD5 {
    //公盐
    private static final String PUBLIC_SALT = "demo" ;
    //十六进制下数字到字符的映射数组
    private final static String[] hexDigits = {"0", "1", "2", "3", "4",
        "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

    /**
     * 用户密码加密，盐值为 ：私盐+公盐
     * @param  password 密码
     * @param  salt 私盐
     * @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{
                //创建具有指定算法名称的信息摘要
                MessageDigest md = MessageDigest.getInstance("MD5");
                //使用指定的字节数组对摘要进行最后更新，然后完成摘要计算
                byte[] results = md.digest(originString.getBytes());
                //将得到的字节数组变成字符串返回
                String resultString = byteArrayToHexString(results);
                return resultString.toUpperCase();
            } catch(Exception ex){
                ex.printStackTrace();
            }
        }
        return null;
    } 

    /**
     * 转换字节数组为十六进制字符串
     * @param     字节数组
     * @return    十六进制字符串
     */
    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();
    }  

    /** 将一个字节转化成十六进制形式的字符串     */
    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];
    }
}