short url 算法

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package com.glodon.paas.coqui.util;import java.security.MessageDigest;public class TokenGenerator {        private final static String[] md5Chars = {"0","1" ,"2" ,"3" ,"4" ,"5" ,"6" ,"7" ,"8" ,"9" ,"A" ,"B" ,"C" ,"D" ,"E" ,"F" };        public static String generate(String str) {               // 可以自定义生成MD5加密字符传前的混合KEY              String key = "glodoncloud";               // 要使用生成URL的字符              String[] chars = new String[] { "a" , "b" , "c" , "d" , "e" , "f" , "g" , "h",                            "i", "j" , "k" , "l" , "m" , "n" , "o" , "p" , "q" , "r" , "s" , "t",                            "u", "v" , "w" , "x" , "y" , "z" , "0" , "1" , "2" , "3" , "4" , "5",                            "6", "7" , "8" , "9" , "A" , "B" , "C" , "D" , "E" , "F" , "G" , "H",                            "I", "J" , "K" , "L" , "M" , "N" , "O" , "P" , "Q" , "R" , "S" , "T",                            "U", "V" , "W" , "X" , "Y" , "Z"              };                             // 对传入网址进行MD5加密              String hex = encodeByMD5(key+str);              String[] resUrl = new String[4];               for (int i = 0; i < 4; i++) {                      // 把加密字符按照8位一组16进制与0x3FFFFFFF进行位与运算                      long hexint = Long.valueOf( "3FFFFFFF", 16) & Long.valueOf( hex.substring(i * 8,(i+1)*8), 16);                     String outChars = "";                      for (int j = 0; j < 6; j++) {                            // 把得到的值与0x0000003D进行位与运算，取得字符数组chars索引                            int index =  (int) (Long.valueOf ("0000003D" , 16) & hexint);                            // 把取得的字符相加                           outChars += chars[index];                            // 每次循环按位右移5位                           hexint = hexint >> 5;                     }                      // 把字符串存入对应索引的输出数组                     resUrl[i] = outChars;              }               return resUrl[0];       }    /**对字符串进行MD5编码*/    private static String encodeByMD5(String originString){        if (originString!=null) {            try {                //创建具有指定算法名称的信息摘要                MessageDigest md5 = MessageDigest. getInstance("MD5");                //使用指定的字节数组对摘要进行最后更新，然后完成摘要计算                byte[] results = md5.digest(originString.getBytes());                //将得到的字节数组变成字符串返回                 String result = byteArrayToHexString(results);                return result;            } catch (Exception e) {                e.printStackTrace();            }        }        return null ;    }     /**    * 轮换字节数组为十六进制字符串    * @param b 字节数组    * @return 十六进制字符串    */    private static String byteArrayToHexString(byte[] b){        StringBuffer resultSb = new StringBuffer();        for(int i=0;i<b.length;i++){            resultSb.append( byteToHexString(b[i]));        }        return resultSb.toString();    }    private static String byteToHexString(byte b){        int n = b;        if(n<0)        n=256+n;        int d1 = n/16;        int d2 = n%16;        return md5Chars [d1] + md5Chars[d2];    }        public static void main(String[] args){              System. out.println(TokenGenerator.generate(UUIDUtil. getUUIDStr()));;       }}
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