Four common post data submission methods

HTTP/1.1 agreement Stipulated HTTP The request method is OPTIONS、GET、HEAD、POST、PUT、DELETE、TRACE、CONNECT These kinds of . among POST It is generally used to submit data to the server , This article mainly discusses POST Several ways to submit data .

We know ,HTTP The agreement is based on ASCII Code transmission , Based on the TCP/IP The application layer specification above the protocol . To regulate HTTP The request is divided into three parts ： Status line 、 Request header 、 Message body . Similar to the following ：

Provisions of the agreement POST The submitted data must be placed in the message body （entity-body） in , But the protocol doesn't specify what encoding method the data must use . actually , Developers can decide the format of the message body , Just send the last HTTP The request satisfies the above format .

however , Data sent out , Only when the server resolves successfully can it make sense . General server-side languages such as  PHP、Python  etc. , And their framework, Both have built-in functions to automatically parse common data formats . The server is usually based on the request header （headers） Medium Content-Type Field to know how the message body in the request is encoded , Then analyze the subject . So when it comes to POST Submit data plan , Contains Content-Type And message body coding . Let's start with them .

application/x-www-form-urlencoded

This should be the most common POST The way to submit data . Browser native form Forms , If not set enctype attribute , Then in the end application/x-www-form-urlencoded How to submit data . The request is similar to the following （ Irrelevant request headers are omitted in this article ）：

First ,Content-Type Is specified as application/x-www-form-urlencoded; secondly , Data submitted as per key1=val1&key2=val2 The way to code ,key and val It's all going on URL transcoding . Most server-side languages have good support for this approach . for example PHP in ,$_POST['title'] Can be obtained title Value ,$_POST['sub'] You can get sub Array .

A lot of times , We use it Ajax When submitting data , It's the same way . for example  JQuery  and  QWrap  Of Ajax,Content-Type The default values are 「application/x-www-form-urlencoded;charset=utf-8」.

multipart/form-data

This is another common POST How to submit data . When we use forms to upload files , Must let form Of enctyped Equal to this value . Let's take a look at a request example ：

This example is a little more complicated . First, a boundary Used to split different fields , In order to avoid the repetition of the text ,boundary It's long and complicated . then Content-Type The data is indicated in mutipart/form-data Encoding , The purpose of this request is boundary What is it . The message body is divided into several parts with similar structure according to the number of fields , Every part is based on --boundary Start , And then the content description information , And then there's the carriage return , Finally, the specific content of the field （ Text or binary ）. If you are transferring files , Also include file name and file type information . The message body ends with --boundary-- Mark the end . About mutipart/form-data The detailed definition of , Please go to  rfc1867  see .

This method is usually used to upload files , The major server languages also have good support for it .

These two kinds mentioned above POST The way of data , It's all browser native support , And at this stage of the original form Forms also Only two ways are supported . But as more and more Web Site , In especial WebApp, All use Ajax After data interaction , We can define a new way to submit data , Bring more convenience to development .

application/json

application/json This Content-Type As a response leader, you must be familiar with . actually , Now more and more people use it as a request header , Used to tell the server that the message body is serialized JSON character string . because JSON The popularity of norms , Except for the lower version IE All other browsers support native JSON.stringify, The server language also has processing JSON Function of , Use JSON No trouble .

JSON Formats support much more complex structured data than key value pairs , It's also useful . Remember when I was working on a project a few years ago , The level of data that needs to be submitted is very deep , I just put the data JSON It was submitted after serialization . But at that time, I put JSON String as val, Still in the key value pair , With x-www-form-urlencoded Mode submission .

Google Of  AngularJS  Medium Ajax function , The default is to submit JSON character string . For example, the following code ：

The final request sent is ：

POST http://www.example.com HTTP/1.1

Content-Type: application/json;charset=utf-8

{ "title":"test","sub":[1,2,3]}

This program , Can easily submit complex structured data , Perfect for RESTful The interface of . All kinds of bag grabbing tools are as follows Chrome Built in developer tools 、Firebug、Fiddler, Will be displayed in a tree structure JSON data , Very friendly . But there are also some server languages that don't support this approach , for example php Can't go through $_POST Object gets the content from the request above . Now , You need to do it yourself ： In the request header Content-Type by application/json when , from php://input Get the original input stream from the , Again json_decode Object . some php The framework has started to do that .

Of course  AngularJS  It can also be configured to use x-www-form-urlencoded How to submit data . If necessary , You can refer to This article .

text/xml

Before my blog Mentioned XML-RPC（XML Remote Procedure Call）. It's a use HTTP As a transport protocol ,XML The remote call specification as an encoding . Typical XML-RPC This is the request ：

XML-RPC Simple protocol 、 Sufficient functions , There are various language implementations . It is also widely used , Such as WordPress Of  XML-RPC Api, Search engines  ping service wait .JavaScript  in , Also have Off the shelf Library Support data interaction in this way , Can support the existing XML-RPC service . however , Personally, I think XML The structure is still too bloated , For general scenes JSON It will be more flexible and convenient .