MD5 加密解密 判断密码是否相等 全套实现方式

package com.mirai.comic.util.md5;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
* @Author:zzh @Email:zhangzihaopk@foxmail.com  @Time:2016/8/5
*/
public class MD5Util {

protected static final Logger logger = LoggerFactory.getLogger(MD5Util.class);
static MessageDigest messageDigest = null;

/**
* 判断新密码和旧密码是否正确  返回true 和 false
*
* @param newStr
* @param oldMD5Str
* @return
*/
public final static boolean checkMD5(String newStr, String oldMD5Str) {
String temp = encoderByMd5(newStr);
return (temp != null && temp.equals(oldMD5Str)) ? true : false;
}

/**
* 对给定的字符串进行加密
*
* @param source
* @return 加密后的16进制的字符串
*/
public final static String encoderByMd5(String source) {
String tmp = source.substring(0, 1)
+ source.subSequence(source.length() - 1, source.length());
tmp = md5(tmp);
return md5(source + tmp);
}

private static String md5(String source) {

if (logger.isDebugEnabled()) {
}
char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
'e', 'f'};
try {

byte[] strTemp = source.getBytes();
// 使用MD5创建MessageDigest对象
MessageDigest mdTemp = MessageDigest.getInstance("MD5");
mdTemp.update(strTemp);
byte[] md = mdTemp.digest();
int j = md.length;
char str[] = new char[j * 2];
int k = 0;
for (int i = 0; i < j; i++) {
byte b = md[i];
str[k++] = hexDigits[b >> 4 & 0xf];
str[k++] = hexDigits[b & 0xf];
}

if (logger.isDebugEnabled()) {
logger.debug("加密后的字符串：" + new String(str));
}
return new String(str);
} catch (Exception e) {
logger.error("md5加密出错：" + source, e);
return null;
}

}

public static String encodeByMD5(String str) {
try {
if (messageDigest == null)
messageDigest = MessageDigest.getInstance("MD5");
messageDigest.reset();
messageDigest.update(str.getBytes("UTF-8"));
} catch (NoSuchAlgorithmException e) {
logger.error("NoSuchAlgorithmException caught!", e);

} catch (UnsupportedEncodingException e) {
logger.error("UnsupportedEncodingException error!", e);
}
if (messageDigest == null)
return "";
byte[] byteArray = messageDigest.digest();

StringBuffer md5StrBuff = new StringBuffer();

for (int i = 0; i < byteArray.length; i++) {
if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
else
md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
}

return md5StrBuff.toString();
}
}