MD5加密密码文件

md5加密是不可逆转的，加密可被撞库强破解，所以加密的时候，尤其用MD5加密登录密码的时候加一个随机盐，可用数字加字符串的形式拼接在密码后面进行加密，邓丽的时候一样用密码加随机盐拼接加密，判断是否相等

package com.example.demo.md5;

import com.example.demo.utils.RandomStringUtils;
import com.example.demo.utils.ReadFileUtils;

import java.io.File;
import java.io.FileInputStream;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.Random;


public class Md5Test {
    public static void main(String[] args) throws Exception {
        String password = "123456789";
        String filePath = "C:/Users/xzw/Desktop/工作文档/12月/15号/15号3.txt";
       // System.out.println(getMD5(password));
       // System.out.println(getMD5(password).length());
        File file = new File(filePath);
       // System.out.println(getMD5(file));
        System.out.println(getMD5(file).length());
    }

    
    public static String getMD5(String str){
        // 获取随机盐
        String randomString = getRandomString(12);
        String MD5 = "";
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            byte[] bytes = (str+randomString).getBytes(StandardCharsets.UTF_8);
            byte[] digest = md5.digest(bytes);
            for (int i = 0; i < digest.length; i++) {
                int j = digest[i];
                j = j & 0x000000ff;
                String s1 = Integer.toHexString(j);
                if (s1.length() == 1){
                    s1 = "0"+s1;
                }
                MD5 += s1;
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
        return MD5;
    }



    //重载,所以用户传入"字符串"或者"文件"都可以解决.

    
    public static String getMD5(File filePathFrom) throws Exception {
        String MD5 = "";
        String filePathTo ="C:/Users/xzw/Desktop/文档/12月/15号/15号2.txt";
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        FileInputStream fis = new FileInputStream(filePathFrom);

        byte[] bytes = new byte[1024 * 5];

        int len = -1;
        while ((len=fis.read(bytes))!=-1) {
            //一部分一部分更新
            md5.update(bytes, 0, len);
            System.out.println(new String(bytes,0,len));
        }

        byte[] digest = md5.digest();
        for (int i = 0; i