Java 实现MD5编码

 

package com.coupon.util;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;

public class Md5Util {
 private static final String HEX_NUMS_STR="0123456789ABCDEF";  
    private static final int 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 {    
        byte[] pwdInDb = hexStringToByte(passwordInDb);  
        byte[] salt = new byte[SALT_LENGTH];  
        System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);  
        MessageDigest md = MessageDigest.getInstance("MD5");  
        md.update(salt);  
        md.update(password.getBytes("UTF-8"));  
        byte[] digest = md.digest();  
        byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];  
        System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);  
        if (Arrays.equals(digest, digestInDb)) {  
            return true;  
        } else {  
            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 {  
        byte[] pwd = null;  
        SecureRandom random = new SecureRandom();   
        byte[] salt = new byte[SALT_LENGTH];  
        random.nextBytes(salt);  
 
        MessageDigest md = null;  
        md = MessageDigest.getInstance("MD5");  
        md.update(salt);  
        md.update(password.getBytes("UTF-8"));  
        byte[] digest = md.digest();  
 
        pwd = new byte[digest.length + SALT_LENGTH];  
        System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);  
        System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);
        return byteToHexString(pwd);  
    }

    public static String getMD5Str(String str) {  
        MessageDigest messageDigest = null;  
 
       try {  
            messageDigest = MessageDigest.getInstance("MD5");  
 
            messageDigest.reset();  
 
            messageDigest.update(str.getBytes("UTF-8"));  
        } catch (NoSuchAlgorithmException e) {  
            System.out.println("NoSuchAlgorithmException caught!");  
            System.exit(-1);  
        } catch (UnsupportedEncodingException e) {  
            e.printStackTrace();  
        }  
 
       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();  
    }
}