之前写程序把base64encode的数据提交到服务器，服务器端出现数据的+号被替换为空格的情况。
查了w3规范手册，原因是如下的编码规范中说的，所以服务器会在解码时把+号改为空格然后给到业务。
所以最好再做个urlencode/urldecode
参考：http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.1
application/x-www-form-urlencoded
This is the default content type. Forms submitted with this content type must be encoded as follows:
- Control names and values are escaped. Space characters are replaced by `+', and then reserved characters are escaped as described in [RFC1738], section 2.2: Non-alphanumeric characters are replaced by `%HH', a percent sign and two hexadecimal digits representing the ASCII code of the character. Line breaks are represented as "CR LF" pairs (i.e., `%0D%0A').
- The control names/values are listed in the order they appear in the document. The name is separated from the value by `=' and name/value pairs are separated from each other by `&'.