package com.mi.util;import java.io.UnsupportedEncodingException;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import java.util.Arrays;public class Md5SaltTool {    private static final String HEX_NUMS_STR="0123456789ABCDEF";       private static final Integer SALT_LENGTH = 12;              /**        * 将16进制字符串转换成字节数组        * @param hex        * @return        */      public static byte[] hexStringToByte(String hex) {           int len = (hex.length() / 2);           byte[] result = new byte[len];           char[] hexChars = hex.toCharArray();           for (int i = 0; i < len; i++) {               int pos = i * 2;               result[i] = (byte) (HEX_NUMS_STR.indexOf(hexChars[pos]) << 4                                | HEX_NUMS_STR.indexOf(hexChars[pos + 1]));           }           return result;       }              /**       * 将指定byte数组转换成16进制字符串       * @param b       * @return       */      public static String byteToHexString(byte[] b) {           StringBuffer hexString = new StringBuffer();           for (int i = 0; i < b.length; i++) {               String hex = Integer.toHexString(b[i] & 0xFF);               if (hex.length() == 1) {                   hex = ‘0‘ + hex;               }               hexString.append(hex.toUpperCase());           }           return hexString.toString();       }              /**       * 验证口令是否合法       * @param password       * @param passwordInDb       * @return       * @throws NoSuchAlgorithmException       * @throws UnsupportedEncodingException       */      public static boolean validPassword(String password, String passwordInDb)               throws NoSuchAlgorithmException, UnsupportedEncodingException {           //将16进制字符串格式口令转换成字节数组           byte[] pwdInDb = hexStringToByte(passwordInDb);           //声明盐变量           byte[] salt = new byte[SALT_LENGTH];           //将盐从数据库中保存的口令字节数组中提取出来           System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);           //创建消息摘要对象           MessageDigest md = MessageDigest.getInstance("MD5");           //将盐数据传入消息摘要对象           md.update(salt);           //将口令的数据传给消息摘要对象           md.update(password.getBytes("UTF-8"));           //生成输入口令的消息摘要           byte[] digest = md.digest();           //声明一个保存数据库中口令消息摘要的变量           byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];           //取得数据库中口令的消息摘要           System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);           //比较根据输入口令生成的消息摘要和数据库中消息摘要是否相同           if (Arrays.equals(digest, digestInDb)) {               //口令正确返回口令匹配消息               return true;           } else {               //口令不正确返回口令不匹配消息               return false;           }       }         /**       * 获得加密后的16进制形式口令       * @param password       * @return       * @throws NoSuchAlgorithmException       * @throws UnsupportedEncodingException       */      public static String getEncryptedPwd(String password)               throws NoSuchAlgorithmException, UnsupportedEncodingException {           //声明加密后的口令数组变量           byte[] pwd = null;           //随机数生成器           SecureRandom random = new SecureRandom();           //声明盐数组变量   12        byte[] salt = new byte[SALT_LENGTH];           //将随机数放入盐变量中           random.nextBytes(salt);             //声明消息摘要对象           MessageDigest md = null;           //创建消息摘要           md = MessageDigest.getInstance("MD5");           //将盐数据传入消息摘要对象           md.update(salt);           //将口令的数据传给消息摘要对象           md.update(password.getBytes("UTF-8"));           //获得消息摘要的字节数组           byte[] digest = md.digest();             //因为要在口令的字节数组中存放盐，所以加上盐的字节长度           pwd = new byte[digest.length + SALT_LENGTH];           //将盐的字节拷贝到生成的加密口令字节数组的前12个字节，以便在验证口令时取出盐           System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);           //将消息摘要拷贝到加密口令字节数组从第13个字节开始的字节           System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);           for(int i=0;i<pwd.length;i++){            System.out.print(pwd[i]);        }        //将字节数组格式加密后的口令转化为16进制字符串格式的口令           return byteToHexString(pwd);       }   }

package com.mi.util;import java.io.UnsupportedEncodingException;import java.security.NoSuchAlgorithmException;import java.util.HashMap;import java.util.Map;public class Md5SaltTest {      private static Map users = new HashMap();                 public static void main(String[] args){               String userName = "zyg";               String password = "123";               registerUser(userName,password);                              userName = "changong";               password = "456";               registerUser(userName,password);                              String loginUserId = "zyg";               String pwd = "1232";               try {                   if(loginValid(loginUserId,pwd)){                       System.out.println("欢迎登陆！！！");                   }else{                       System.out.println("口令错误，请重新输入！！！");                   }               } catch (NoSuchAlgorithmException e) {                   // TODO Auto-generated catch block                   e.printStackTrace();               } catch (UnsupportedEncodingException e) {                   // TODO Auto-generated catch block                   e.printStackTrace();               }            }                      /**           * 注册用户           *            * @param userName           * @param password           */          public static void registerUser(String userName,String password){               String encryptedPwd = null;               try {                   encryptedPwd = Md5SaltTool.getEncryptedPwd(password);                   users.put(userName, encryptedPwd);                                  } catch (NoSuchAlgorithmException e) {                   // TODO Auto-generated catch block                   e.printStackTrace();               } catch (UnsupportedEncodingException e) {                   // TODO Auto-generated catch block                   e.printStackTrace();               }           }                      /**           * 验证登陆           *            * @param userName           * @param password           * @return           * @throws UnsupportedEncodingException            * @throws NoSuchAlgorithmException            */          public static boolean loginValid(String userName,String password)                        throws NoSuchAlgorithmException, UnsupportedEncodingException{                /*String loginUserId = "zyg";                  String pwd = "1232";*/             String pwdInDb = (String)users.get(userName);               if(null!=pwdInDb){ // 该用户存在                       return Md5SaltTool.validPassword(password, pwdInDb);               }else{                   System.out.println("不存在该用户！！！");                   return false;               }           }}