![]() ![]() If the preflight hits a server that is CORS-enabled, the server knows what a preflight request is and can respond appropriately. 又想了一下为什么之前的项目一直没有这个问题,其实是因为很多框架以及帮我们实现好了,比如说. The concept of a preflight was introduced to allow cross-origin requests to be made without breaking existing servers that depend on the browser’s same-origin policy. 1 Like bolerodan August 28, 2017, 2:37pm 2 This is a CORS issue. ![]() Origin ‘ ’ is therefore not allowed access. 有人给我把请求头信息更改了!Authorization不见了,甚至连req.method都变成了OPTIONS,而不是GET。 罪魁祸首-预检(Pre-flight) For a simple request the server must only allow the origin by adding the following header: Access-Control-Allow-Origin: With a preflighted request the browser will automatically send an initial request with the method OPTIONS to determine weather the actual request is safe to send. Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource. parse application/json and look for raw textĪpp.use(bodyParser.urlencoded(), userRoutes) Res.header("Access-Control-Allow-Credentials", "true") The server can then respond to the pre-flight request with a collection of headers: Access-Control-Allow-Origin: Defines which origins may have access to the resource. Res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Authorization, Access-Control-Allow-Credentials") This is not a guaranteed fix, and will only work if the receiving domain is configured to respond in JSONP format. Res.header("Access-Control-Allow-Methods", "PUT, GET, POST, DELETE, OPTIONS") Solution 2: set headers the correct way 8. The OPTIONS request carries the Origin header, along with some other information about the request (check out the CORS explainer. Res.header("Access-Control-Allow-Origin", "*") The browser in the background creates and makes it as its part of the CORS specification standard. The web apps code doesnt explicitly make it. ![]() ![]() This header is required if the request has an Access-Control-Request-Headers header. var url= ' $.ajax().这两天在使用NodeJS Express搭建REST服务器时遇到一个很典型的AJAX跨域包含自定义请求头问题(用于身份验证),在花了大半天时间排查问题后发现自己对CORS真正的理解还很不够,尤其是pre-flight。 需求描述 When custom request headers, authentication, or other conditions exist in the cross-origin request, the browser makes an additional HTTP call. The Access-Control-Allow-Headers response header is used in response to a preflight request which includes the Access-Control-Request-Headers to indicate which HTTP headers can be used during the actual request. I'm calling this function from my asp.net form and getting following error on firebug console while calling ajax.Ĭross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at (Reason: CORS header 'Access-Control-Allow-Origin' missing). This header contains an Access-Control-Allow-Origin key, to specify which origins can access the server’s resources. ![]()
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