短网址的原理与生成方法（Java实现）

public static string[] ShortUrl(string url) 
{ 
 //可以自定义生成MD5加密字符传前的混合KEY 
 string key = "Leejor"; 
 //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 = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(key + url, "md5"); 
 
 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 
  int hexint = 0x3FFFFFFF & Convert.ToInt32("0x" + hex.Substring(i * 8, 8), 16); 
  string outChars = string.Empty; 
  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 = 0x0000003D & 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; 
} 

ShortUrl(http://www.me3.cn)[0]; //得到值fAVfui 
ShortUrl(http://www.me3.cn)[1]; //得到值3ayQry 
ShortUrl(http://www.me3.cn)[2]; //得到值UZzyUr 
ShortUrl(http://www.me3.cn)[3]; //得到值36rQZn 

CREATE TABLE mappedURL (的CREATE TABLE mappedURL（ 
shortCode char(6) not null, 
lognURL text not null, 
PRIMARY KEY shortCodeInd (shortCode), 
);