時下,短網址應用已經在全國各大微博上開始流行了起來。例如QQ微博的url.cn,新郎的t.cn等。我們在新浪微博上發佈網址的時候,微博會自動判別網址,並將其轉換,例如:http://t.cn/hrYnr0。爲什麼要這樣做的,原因我想有這樣幾點:
1、微博限制字數爲140字一條,那麼如果我們需要發一些連接上去,但是這個連接非常的長,以至於將近要佔用我們內容的一半篇幅,這肯定是不能被允許的,所以短網址應運而生了。
2、短網址可以在我們項目裏可以很好的對開放級URL進行管理。有一部分網址可以會涵蓋性、暴力、廣告等信息,這樣我們可以通過用戶的舉報,完全管理這個連接將不出現在我們的應用中,應爲同樣的URL通過加密算法之後,得到的地址是一樣的。
3、我們可以對一系列的網址進行流量,點擊等統計,挖掘出大多數用戶的關注點,這樣有利於我們對項目的後續工作更好的作出決策。
以上三點純屬個人觀點,因爲在我接下來的部分項目中會應用到,所以就瞭解了一下,下面先來看看短網址映射算法的理論(網上找到的資料):
① 將長網址用md5算法生成32位簽名串,分爲4段,,每段8個字符;
② 對這4段循環處理,取每段的8個字符, 將他看成16進制字符串與0x3fffffff(30位1)的位與操作,超過30位的忽略處理;
③ 將每段得到的這30位又分成6段,每5位的數字作爲字母表的索引取得特定字符,依次進行獲得6位字符串;
④ 這樣一個md5字符串可以獲得4個6位串,取裏面的任意一個就可作爲這個長url的短url地址。
我們並不一定說得到的URL是唯一的,但是我們能夠取出4組URL,這樣幾乎不會出現太大的重複。
首先,請大家瞭解在Java中如何用MD5來加密字符串得到32位的加密後的字符串,下面是我已經封裝好的Java MD5算法:
【MD5encry.class】
package com.example.demo_shorturl;
import java.security.MessageDigest;
/**
* ClassName:MD5encry <br/>
* Function: TODO ADD FUNCTION. <br/>
* Reason: TODO ADD REASON. <br/>
* Date: 2014-8-13 上午9:51:15 <br/>
* @author Geek_AnJon
* @version
* @since JDK 1.6
* @see
*/
public class MD5encry {
private final static String[] hexDigits = {
"0", "1", "2", "3", "4", "5", "6", "7",
"8", "9", "a", "b", "c", "d", "e", "f"};
public 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 hexDigits[d1] + hexDigits[d2];
}
public static String MD5Encode(String origin){
String resultString = null;
try {
resultString=new String(origin);
MessageDigest md = MessageDigest.getInstance("MD5");
resultString.trim();
resultString=byteArrayToHexString(md.digest(resultString.getBytes("UTF-8")));
}catch (Exception ex){}
return resultString;
}
public static void main(String[] args)
{
String data = "189022881112011111118:09sz0000123456789987654321";
System.out.println(MD5Encode(data));
}
}
【ShortUrl.class】package com.example.demo_shorturl;
/**
* ClassName:ShortUrl <br/>
* Function: TODO ADD FUNCTION. <br/>
* Reason: TODO ADD REASON. <br/>
* Date: 2014-8-13 上午9:48:34 <br/>
* @author Geek_AnJon
* @version
* @since JDK 1.6
* @see
*/
public class ShortUrl {
public static void main(String[] args) {
String url = "http://www.baidu.com";
for (String string : ShortText(url)) {
print(string);
}
}
public static String[] ShortText(String string){
String key = "Geek"; //自定義生成MD5加密字符串前的混合KEY
String[] chars = new String[]{ //要使用生成URL的字符
"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"
};
String hex = MD5encry.MD5Encode(key + string);
int hexLen = hex.length();
int subHexLen = hexLen / 8;
String[] ShortStr = new String[4];
for (int i = 0; i < subHexLen; i++) {
String outChars = "";
int j = i + 1;
String subHex = hex.substring(i * 8, j * 8);
long idx = Long.valueOf("3FFFFFFF", 16) & Long.valueOf(subHex, 16);
for (int k = 0; k < 6; k++) {
int index = (int) (Long.valueOf("0000003D", 16) & idx);
outChars += chars[index];
idx = idx >> 5;
}
ShortStr[i] = outChars;
}
return ShortStr;
}
private static void print(Object messagr){
System.out.println(messagr);
}
}
現在可以直接使用ShortText(url)方法獲取短鏈接地址了