java实现MD5加密

package com.zyg.security.md5;import java.io.UnsupportedEncodingException;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import java.util.Arrays;public class MyMD5Util {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<a href="http://lib.csdn.net/base/mysql" class='replace_word' title="MySQL知识库" target='_blank' style='color:#df3434; font-weight:bold;'>数据库</a>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);//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);}}

测试类代码：

package com.zyg.security.md5;import java.io.UnsupportedEncodingException;import java.security.NoSuchAlgorithmException;import java.util.HashMap;import java.util.Map;public class Client {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 blocke.printStackTrace();} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();} }/** * 注册用户 *  * @param userName * @param password */public static void registerUser(String userName,String password){String encryptedPwd = null;try {encryptedPwd = MyMD5Util.getEncryptedPwd(password);users.put(userName, encryptedPwd);} catch (NoSuchAlgorithmException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.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 pwdInDb = (String)users.get(userName);if(null!=pwdInDb){ // 该用户存在return MyMD5Util.validPassword(password, pwdInDb);}else{System.out.println("不存在该用户！！！");return false;}}}