package com.troy.jpa.util;

import java.security.MessageDigest;

public class MD5Util {

    private static final char[] DIGITS_LOWER = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

    //通过MD5进行加密
    public static String encrpytionByMd5(String data) throws Exception {
        //获取MD5的摘要
        MessageDigest messageDigest = MessageDigest.getInstance("MD5");
        //使用指定的直接更新摘要
        messageDigest.update(data.getBytes());
        //获取计算过后的数据
        byte[] digest = messageDigest.digest();
        //将密文转成32为，输出成字符串
        return new String(encodeHex(digest));
    }

    //字节数据装换
    private static char[] encodeHex(byte[] data) {
        //获取数据字节长度
        int n = data.length;
        //a << b 的意思就是a*2的b次方，>>就是除以
        char[] out = new char[n << 1];
        int i = 0;
        for(int v = 0; i < n; ++i) {
            out[v++] = DIGITS_LOWER[(240 & data[i]) >>> 4];
            out[v++] = DIGITS_LOWER[15 & data[i]];
        }
        return out;
    }

    public static void main(String[] args) {
       try {
           String data = "123456";
           String md5 = encrpytionByMd5(data);
           System.out.println(md5);
       } catch (Exception e) {
           e.printStackTrace();
       }
    }
}