HTTP 协议是否支持响应标头中的多种内容类型？
我想知道我是否可以返回响应标头
Content-Type: application/json text/json
，或者这不合法吗？
HTTP 协议规定 Content-Type 应该是 mediaType 并且 mediaType 定义如下：
media-type = type "/" subtype *( ";" parameter )
type = token
subtype = token
但我无法解释这意味着什么，有人可以启发我吗？
谢谢！
I'm wondering if I can return the response header
Content-Type: application/json text/json
or isn't this legal?
The HTTP protocol states that Content-Type should be of mediaType and that mediaType is defined as the following:
media-type = type "/" subtype *( ";" parameter )
type = token
subtype = token
But I'm having trouble interpreting what this means, can anyone enlighten me?
Thanks!
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您需要查看标头字段的定义：
http://greenbytes .de/tech/webdav/rfc2616.html#rfc.section.14.17
Content-Type = "Content-Type" ":" 媒体类型，
因此需要单一媒体类型，由您上面引用的语法定义。
所以答案是：单个类型/子类型，后跟可选参数。
You need to look at the definition of the header field:
http://greenbytes.de/tech/webdav/rfc2616.html#rfc.section.14.17
Content-Type = "Content-Type" ":" media-type
so it takes a single media-type, which is defined by the grammar you quoted above.
So the answer is: a single type/subtype, followed by optional parameters.
不可以。正如接受的答案中所指出的，标头值本身不允许有多个值，也不允许发送多个 Content-Type 标头：
https://www.rfc-editor.org/rfc/rfc7230#section -3.2.2
没有一个“转义子句”成立，因为
media-type不允许使用逗号分隔的值列表，并且Content-Type显然也不是一个众所周知的例外。No. As pointed out in the accepted answer, the header value itself does not allow for multiple values, and it is also not allowed to send multiple Content-Type headers:
https://www.rfc-editor.org/rfc/rfc7230#section-3.2.2
None of the "escape clauses" holds, because
media-typedoes not allow a comma-separated list of values, andContent-Typeevidently is not a well-known exception, either.