请求头字段 Access-Control-Allow-Headers 在预检响应中不被允许 [英] Request header field Access-Control-Allow-Headers is not allowed by itself in preflight response

问题描述

我多次遇到 CORS 问题，通常可以修复它，但我想通过从 MEAN 堆栈范例中看到这一点来真正理解.

I have come across CORS issues multiple times and can usually fix it but I want to really understand by seeing this from a MEAN stack paradigm.

在我简单地在我的 express 服务器中添加中间件来捕获这些东西之前，但看起来有某种预挂钩错误地处理了我的请求.

Before I simply added middleware in my express server to catch these things, but it looks like there is some kind of pre-hook that is erroring out my requests.

预检响应中的 Access-Control-Allow-Headers 不允许请求头字段 Access-Control-Allow-Headers

Request header field Access-Control-Allow-Headers is not allowed by Access-Control-Allow-Headers in preflight response

我认为我可以做到这一点:

I assumed that I could do this:

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Headers","*")
})

或等价物，但这似乎无法解决问题.我当然也试过了

or the equivalent but this doesn't seem to fix it. I also of course tried

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Headers","Access-Control-Allow-Headers")
})

仍然没有运气.

推荐答案

当您开始使用自定义请求标头时，您将获得 CORS 预检.这是一个使用 HTTP OPTIONS 动词的请求，并包含多个标头，其中之一是 Access-Control-Request-Headers 列出客户端想要包含在请求.

When you start playing around with custom request headers you will get a CORS preflight. This is a request that uses the HTTP OPTIONS verb and includes several headers, one of which being Access-Control-Request-Headers listing the headers the client wants to include in the request.

您需要使用适当的 CORS 标头回复该 CORS 预检才能完成此工作.其中之一确实是Access-Control-Allow-Headers.该标头需要包含与 Access-Control-Request-Headers 标头包含的相同的值(或更多).

You need to reply to that CORS preflight with the appropriate CORS headers to make this work. One of which is indeed Access-Control-Allow-Headers. That header needs to contain the same values the Access-Control-Request-Headers header contained (or more).

https://fetch.spec.whatwg.org/#http-cors-protocol更详细地解释了此设置.

https://fetch.spec.whatwg.org/#http-cors-protocol explains this setup in more detail.

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