MD5实现加密

import java.security.MessageDigest;

public class Security {
    public static String encodeToMD5(String s) throws Exception{
        if (s == null)
            return null;
        String digstr = "";
        MessageDigest MD = MessageDigest.getInstance("MD5");

        byte[] oldbyte = new byte[s.length()];
        for (int i = 0; i < s.length(); i++) {
            oldbyte[i] = (byte) s.charAt(i);
        }
        MD.update(oldbyte);
        byte[] newbyte = MD.digest(oldbyte);
        for (int i = 0; i < newbyte.length; i++) {
            digstr = digstr + newbyte[i];
        }

        return digstr;
    }

    public static void main(String[] args) {
    	try {
			String pw = encodeToMD5("huang");
			System.out.println("md5加密后:" + pw);
    	} catch (Exception e) {
			e.printStackTrace();
		}
    	
    }
}

首先, md5 无法解密.

登录密码加密的实现思路应该是:

1. 用户设置密码的时候,将密码进行md5加密,然后存入数据库,
2. 用户登录的时候,同样用md5算法加密密码,然后用sql语句去数据库进行比对. 而不是将密码取出来解密了在比对.