WebApi：* / *媒体类型处理(WebApi: */* media type handling)

WebApi：* / *媒体类型处理(WebApi: */* media type handling)

在我的应用程序中，我向Api控制器发出了一些JavaScript请求，以获得一些html格式的字符串。 当这些请求使用Accept: */* HTTP头（jQuery $.get方法）进行时，默认情况下使用JsonMediaTypeFormatter ，数据以JSON格式的Content-Type: application/json 。

我想要的是将*/*请求作为text/html 。 所以我试图创建一个支持*/*媒体类型的自定义MediaTypeFormatter ，但它给了我以下错误

*/*的'MediaTypeHeaderValue'不能用作支持的媒体类型，因为它是一个媒体范围。

或者，我总是可以在我的请求中提供正确的预期数据类型，但我很好奇是否有办法处理*/*媒体类型。

In my application I'm making some javascript requests to my Api Controllers to get some html formatted strings. When those requests are made with Accept: */* HTTP header (jQuery $.get method), so by default JsonMediaTypeFormatter is used and the data is returned with Content-Type: application/json in JSON format.

What I would like is to handle */* requests as text/html. So I tried to create a custom MediaTypeFormatter that supports */* media type, but it gives me the following error

The 'MediaTypeHeaderValue' of */* cannot be used as a supported media type because it is a media range.`

Alternatively I could always provide correct expected data types in my requests, but I'm curious if there's a way to handle */* media types.

最满意答案

上述行为是由于以下原因：

Web API中的默认con-neg算法具有以下选择响应格式化程序的优先顺序 ：

基于媒体类型映射的格式符匹配。 基于请求接受标头的媒体类型的格式符匹配。 格式符匹配基于请求内容类型头的媒体类型。 格式化程序匹配是否可以序列化响应数据的类型。

现在，JsonMediaTypeFormatter带有一个名为XmlHttpRequestHeaderMapping的内置媒体类型映射，该映射检查传入的请求并查看请求是否具有x-requested-with: XMLHttpRequest的头部x-requested-with: XMLHttpRequest并且如果没有accept头部或者只有Accept头部*/* 。

由于您的请求大多可能看起来像下面，根据优先顺序JsonMediaTypeFormatter被选为写回应的那个：

GET /api/something Accept: */* x-requested-with: XMLHttpRequest

你的问题的解决方案是明确要求“文本/ HTML”，因为这是你所期待的。

GET /api/something Accept: text/html x-requested-with: XMLHttpRequest

我写了很多关于内容协商的非常老的博客文章： http : //blogs.msdn.com/b/kiranchalla/archive/2012/02/25/content-negotiation-in-asp-net-mvc4-web-api -β-部分1.aspx http://blogs.msdn.com/b/kiranchalla/archive/2012/02/27/content-negotiation-in-asp-net-mvc4-web-api-beta-part-2.aspx

The above behavior is due to the following:

The default con-neg algorithm in Web API has the following precedence order of choosing the formatter for response:

Formatter match based on Media Type Mapping. Formatter match based on Request Accept header's media type. Formatter match based on Request Content-Type header's media type. Formatter match based on if it can serialize the response data’s Type.

Now, JsonMediaTypeFormatter comes with a built-in media type mapping called XmlHttpRequestHeaderMapping which inspects an incoming request and sees if the request has the header x-requested-with: XMLHttpRequest and also if there is no accept header or if the Accept header is only having */*.

Since your request is mostly probably looking like below, according to the precedence order JsonMediaTypeFormatter is chosen as the one writing the response:

GET /api/something Accept: */* x-requested-with: XMLHttpRequest

A solution for your issue would be is to explicitly ask for "text/html" as this is what you are expecting.

GET /api/something Accept: text/html x-requested-with: XMLHttpRequest

Couple of very old blog posts about Content negotiation that I wrote: http://blogs.msdn.com/b/kiranchalla/archive/2012/02/25/content-negotiation-in-asp-net-mvc4-web-api-beta-part-1.aspx http://blogs.msdn.com/b/kiranchalla/archive/2012/02/27/content-negotiation-in-asp-net-mvc4-web-api-beta-part-2.aspx