问题描述
我遇到了这个有趣的标题：
I came across this interesting header:
Content-Type: charset=utf-8
回答者说这个语法是由，但我不是在提供的链接中看到它的
。这是有效的语法，如果是这样，那么
具体是这个定义的吗？
The answerer says that this syntax is defined by RFC 2616, but I am notseeing it in the provided link. Is this valid syntax, and if so wherespecifically is this defined?
推荐答案
是这样的：
And the media-type production is this:
media-type = type "/" subtype *( ";" parameter )
type = token
subtype = token
这表示虽然参数部分（例如 charset = utf-8 是可选的，但类型/subtype part不是 - 也就是说，媒体类型必须有一个斜杠后跟一个子类型。
That says that while the parameter part (e.g., charset=utf-8 is optional, the type "/" subtype part is not—that is, a media type must have type followed by a slash followed by a subtype.
所以 Content-Type：charset = utf-8 无效每个语法都没有特别定义，也没有在规范/权威的任何地方特别定义。
So Content-Type: charset=utf-8 isn’t valid syntax per that, and not specially defined anywhere else normatively/authoritatively to be either.
RFC 2616实际上已被RFC 7231和其他几个RFC（当前的HTTP RFC）淘汰。
RFC 2616 is actually obsoleted by RFC 7231 and several other RFCs (the current HTTP RFCs).
但是RFC 7231的相应部分为这种情况定义了基本相同的产品：
But the corresponding parts of RFC 7231 define essentially the same productions for this case:
是这样的：
The production in RFC 7231 for the value of the Content-Type header is this:
Content-Type = media-type
并且是这样的：
And the media-type production is this:
media-type = type "/" subtype *( OWS ";" OWS parameter )
type = token
subtype = token
没有其他规范废弃或取代该部分 - RFC 7231仍然是授权ive on this。
And no other spec obsoletes or supersedes that part—RFC 7231 remains authoritative on this.
大多数编程语言都有良好的媒体类型解析库，用于
语法检查;示例：
Most programming languages have good media-type parsing libs forsyntax checking; example:
npm install content-type
node -e "var ct = require('content-type'); ct.parse('charset=utf-8')"
=> TypeError: invalid media type
node -e "var ct = require('content-type'); ct.parse('image; charset=utf-8')"
=> TypeError: invalid media type
这篇关于Content-Type仅限charset的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！