HTTP短URL实现原理浅析

厘短链

使用这个网址生成短连接，比如：

原链接

https://realchuan.github.io/2021/10/12/QT%E5%AE%9E%E7%94%A8%E5%B0%8F%E6%8A%80%E5%B7%A7%EF%BC%88%E6%83%B3%E5%88%B0%E5%B0%B1%E6%9B%B4%E6%96%B0%EF%BC%89/#more

短连接

https://dlj.li/zCFb4

把这个Url输入到浏览器，以下是请求过程

1. DNS首先解析获得 dlj.li 的IP地址；

2. 然后发起HTTP GET请求，查询 zCFb4；

3. https://dlj.li服务器就会把请求通过HTTP 301转到对应的原链接 ;

   1. HTTP/1.1 301 Moved Permanently\r\n
              [Expert Info (Chat/Sequence): HTTP/1.1 301 Moved Permanently\r\n]
              Response Version: HTTP/1.1
              Status Code: 301
              [Status Code Description: Moved Permanently]
              Response Phrase: Moved Permanently
          Date: Fri, 22 Jul 2022 09:04:42 GMT\r\n
          Transfer-Encoding: chunked\r\n
          Connection: keep-alive\r\n
          Cache-Control: max-age=3600\r\n
          Expires: Fri, 22 Jul 2022 10:04:42 GMT\r\n
          Location: https://dlj.li/404\r\n
           [truncated]Report-To: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=iJMIJ0Z5jjADPMhHYaGyyEeZ5XY7SMzuPuolAYfLXrDfYip4FNLGc6MAQEXrJ4nzKGCnpa6oVMOlg%2B3hgf8Rgtz0kILPv2mJxvPaZy2aeOJy%2F0p6gt7Mhkg%3D"}],"group":"cf-nel","
          NEL: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}\r\n
          Vary: Accept-Encoding\r\n
          Server: cloudflare\r\n
          CF-RAY: 72eb02ac6b767d7a-LAX\r\n
          alt-svc: h3=":443"; ma=86400, h3-29=":443"; ma=86400\r\n
          \r\n
          [HTTP response 1/1]
          [Time since request: 0.191952000 seconds]
          [Request in frame: 77]
          [Request URI: http://dlj.li/404]
          HTTP chunked response
          File Data: 0 bytes
      

4. 后面的解析过程就和平常网址解析是一样的了。

缩短URL的实现有很多，介绍一种最简单的（其他也大同小异）

在数据建一张表（自增ID），存入原URL，生成的ID直接拼接到服务器域名后部；

只要保证这个ID在表中唯一（使用其他方式也可以）；

理论上5位长度假设一位上可以用52个字符，那就是可以存52的5次方是380,204,032个短URL，实际肯定比这个多。