使用content type application/json发送序列化为json而不是text/plain的对象是否有性能优势？
I know many frameworks (like Spring) can map and serialize data based on the content type, but in general I find that this process is easy enough that it isn't a compelling reason to use application/json over text/plain for JSON objects.
示例:
xhr.setRequestHeader("Content-type","text/plain");
// or
xhr.setRequestHeader("Content-type","application/json");
xhr.send(JSON.stringify({"foo": "bar"}));
Let's assume that you are talking about using JSON versus a custom format (using MIME type text/plain) for passing structured data.
Performance may be broken down into different components; e.g.
理论上，我们可以说，假设优化设计和实现的自定义格式不会比JSON慢，也不会比JSON密度低.("证据"是显而易见的. Select JSON的最佳实现，并对格式进行一些不会影响性能的微小更改.)
但实际上，您必须比较实际格式和实际实现的性能.因此，答案是性能实际上取决于您在设计和实现格式及其相关编码/解码软件方面做得有多好.此外，这还取决于如何实现JSON.有许多具有不同性能特征的服务器端JSON库，以及将数据从"本机"数据 struct 映射到"本机"数据 struct 的不同方式.
这让我们看到了JSON(和XML)相对于自定义格式的真正优势.
With JSON and XML, there are libraries available for any mainstream language you chose to use to assist in encoding and decoding content. With a custom format, you have to roll your own encoding / decoding for the client and server sides.
With JSON and XML, there are standards that say what is well-formed that allow other people to implement encoders / decoders. With a custom format, you have to write the specification yourself if you want other people to be able to implement your format.
易变易变.发展基于JSON/XML的格式是一件相对简单的事情.但是使用自定义格式，您(至少)有更多的工作要做，并且根据您的设计 Select ，这可能非常困难.
For most application, these issues matter far more than performance. And that's why JSON or XML are widely used.
FOLLOWUP个
但是，如果相反，您假设我没有使用自定义实现，并将发送MIME类型为text/Plain的JSON与MIME类型为application/json的发送JSON进行比较，会发生什么呢？
Then the answer is that it makes almost no performance difference.
In addition, using an inaccurate MIME type is (arguably) a violation of the HTTP specs. If you do this:
it is more likely that the receiver will mishandle the response; e.g. fail to decode it, or show it in a browser window, and
假设客户端或服务器使用HTTP内容类型协商，则可能会中断该协商.
In short, I can think of no good reason to do this1, and a few good reasons not to do it.
1 - In general. Obviously, there will be edge cases ...