How to submit data through post

When it comes to uploading data , We will naturally say Json/XML, But these are data formats . But the way of data uploading has been ignored by me all the time . The current understanding is , Four common schemes are commonly used to encode local data , adopt Content-Type To specify the data upload method , At the same time through Content-Length To specify the data length .

application/x-www-form-urlencoded

This should be the most common way to submit . In native forms From, If not set enctype attribute , This scheme will be adopted by default to upload data . Its HTTP The requested information is as follows ：

POST http://www.example.com HTTP/1.1
Content-Type: application/x-www-form-urlencoded;charset=utf-8

titile=%E6%B5%8B%E8%AF%95&body=%E6%B5%8B%E8%AF%95

It can be seen that ,Body Part of the data goes through URL After transcoding , With key1=val1&key2=val2 In the form of . In many cases , This is all Post Default submission method , But because it uses three characters to represent a Non-ASCII character , So the efficiency is relatively low .

multipart/form-data

Form enctype Attribute currently has two attribute values , One default is application/x-www-form-urlencoded, The other way is multipart/form-data 了 . This sending method is designed to support sending binary data to the server . Its HTTP The requested information is as follows ：

POST http://www.example.com HTTP/1.1
Content-Type:multipart/form-data; boundary=aHR0cDovL3d3dy5leGFtcGxlLmNvbQ

--aHR0cDovL3d3dy5leGFtcGxlLmNvbQ
Content-Disposition: form-data; name="city"

Test
--aHR0cDovL3d3dy5leGFtcGxlLmNvbQ
Content-Disposition: form-data; name="file"; filename="test.png"
Content-Type: image/png
Content-Transfer-Encoding: binary

PNG ... content of test.png ...
--aHR0cDovL3d3dy5leGFtcGxlLmNvbQ--

As you can see from the above example , The format of this sending method includes multiple Part, Every Part Use randomly generated --boundary To segment , The last line uses --boundary-- ending . Every Part Must contain a Content-Disposition Field , This field contains a type and name Parameters of , If there are files uploaded , We need another one filename Parameters of , among type The value is form-data. Here you can also see the sending pictures Part It also uses Content-Type, If it can be the type of binary file when sending , Then the corresponding type value will be filled , If you can't recognize it , Will adopt application/octet-stream As type value , If multiple documents are summarized into one form item , Will use multipart/mixed As attribute value . At the same time , If Part The content of is the same as the default encoding In a different way , Will have a Content-Transfer-Encoding Property to specify the Part Coding method of .

application/json and text/xml

These two methods can be seen from the name of its transmission content , Not much .

Reference resources
https://imququ.com/post/four-ways-to-post-data-in-http.html
https://www.jianshu.com/p/29e38bcc8a1d