再次回顾post请求中的enctype

1,关于multipart/form-data,参考rfc1867

2.关于post的集中编码格式,参考MDN

A brief introduction to the submit methods

An html <form> can be sent in four ways:

• using the POST method and setting the enctype attribute to application/x-www-form-urlencoded (default);
• using the POST method and setting the enctype attribute to text/plain;
• using the POST method and setting the enctype attribute to multipart/form-data;
• using the GET method (in this case the enctype attribute will be ignored).

Now, consider the submission of a form containing only two fields, named foo and baz. If you are using the POST method the server will receive a string similar to one of the following three examples, depending on the encoding type you are using:

• Method: POST; Encoding type: application/x-www-form-urlencoded (default):

  Content-Type: application/x-www-form-urlencoded
  
  foo=bar&baz=The+first+line.%0D%0AThe+second+line.%0D%0A

• Method: POST; Encoding type: text/plain:

  Content-Type: text/plain
  
  foo=bar
  baz=The first line.
  The second line.

• Method: POST; Encoding type: multipart/form-data:(上传文件会用到)

  Content-Type: multipart/form-data; boundary=---------------------------314911788813839
  
  -----------------------------314911788813839
  Content-Disposition: form-data; name="foo"
  
  bar
  -----------------------------314911788813839
  Content-Disposition: form-data; name="baz"
  
  The first line.
  The second line.
  
  -----------------------------314911788813839--

However, if you are using the GET method, a string like the following will be simply added to the URL:

?foo=bar&baz=The%20first%20line.%0AThe%20second%20line.

关于multipart/form-data有个小插曲,就是在使用Jquery 的Formdata对象进行ajax上传文件时,ajax有个content-type的设置,默认是application/x-www-form-urlencoded,但是,如果上传文件,必须使用multipart/form-data,而且必须设定分隔符,所以,此项不需要设置(值为false),然后通过HTML表单创建FormData对象即可(var formData = new FormData(someFormElement))关于

multipart/form-data的请求头必须包含一个特殊的头信息：Content-Type，且其值也必须规定为multipart/form-data，同时还需要规定一个内容分割符用于分割请求体中的多个post的内容，如文件内容和文本内容自然需要分割开来，不然接收方就无法正常解析和还原这个文件了。具体的头信息如下：

[html] view plain copy

1. Content-Type: multipart/form-data; boundary=${bound}