url编码

http://blog.youkuaiyun.com/yzhz/article/details/1676796

http://www.ruanyifeng.com/blog/2010/02/url_encoding.html

关于URL编码，RFC1738做 了如下的规定：

“Only alphanumerics [0-9a-zA-Z], the special characters “$-_.+!*’(),” [not including the quotes - ed], and reserved characters used for their reserved purposes may be used unencoded within a URL.”

RFC继而说明了保留字、特殊符号、不安全字符的含义——也就是说，下面三类字符可以不经过编码，直接出现在URL上：

[0-9a-zA-Z]

特殊字符：$-_.+!*’(),

保留字符：&/:;=?@