Don't turn down, three sentences to clarify the origin of cross domain resource request errors

Don't turn down , Three sentences to clarify the origin of cross domain resource request errors

Many students always encounter cross domain problems in their work , For example, such an error report

Access to XMLHttpRequest at ' 'http://test.com.cn/get' from origin 'http://local.com.cn:8080' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

In fact, it is very simple to judge whether it is cross domain

Only agreement 、 domain name 、 Only when the ports are all the same can they be considered under the same domain , In other cases, there are cross domain ！

The so-called agreement ：https and http

The so-called domain name ：test.com.cn and ai.test.com.cn It's different

So called port ：80 Port and 8080 Ports are naturally different

Of course , Cross domain problems do not necessarily exist .

Because the cross domain problem is that the browser is for ajax A security restriction of a request ： A page started ajax request , It can only be the path of the same domain name as the current page , This can effectively organize cross site attacks . in other words , The cross domain problem is aimed at ajax The limitation of , It's the browser's self-protection behavior .

Usually we use cors To solve the cross domain , You need to do some configuration for the back-end development students .

For simple and complex requests , There are two ways to deal with it . We will write an article on this tomorrow .

ps:CORS, yes HTML5 A feature of , It defines a way for browsers to interact with servers to determine whether cross domain requests are allowed .

You can add header information in the background to correspond to the front end , The permissions of the front-end sending request and the background control are compared with each other , So as to obtain the relevant permissions of the background , In this way, there is no cross domain problem .