I've been reading about Access-Control-Allow-Origin because it seems effective at allowing cross domain requests since I have access to the external site. My question ism how do I use Access-Control-Allow-Origin to allow cross domain requests. I tried this (don't laugh) (by the way all I want is for a single number, 1 or 0 to be returned)
<html>
<head>
Access-Control-Allow-Origin: *
</head>
<body>
1
</body>
</html>
Am I close? Thanks for your help. If there is an easier way to do a simple cross-domain request let me know.
This question is related to
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cross-domain
same-origin-policy
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That is an HTTP header. You would configure your webserver or webapp to send this header ideally. Perhaps in htaccess or PHP.
Alternatively you might be able to use
<head>...<meta http-equiv="Access-Control-Allow-Origin" content="*">...</head>
I do not know if that would work. Not all HTTP headers can be configured directly in the HTML.
This works as an alternative to many HTTP headers, but see @EricLaw's comment below. This particular header is different.
Caveat
This answer is strictly about how to set headers. I do not know anything about allowing cross domain requests.
About HTTP Headers
Every request and response has headers. The browser sends this to the webserver
GET /index.htm HTTP/1.1
Then the headers
Host: www.example.com
User-Agent: (Browser/OS name and version information)
.. Additional headers indicating supported compression types and content types and other info
Then the server sends a response
Content-type: text/html
Content-length: (number of bytes in file (optional))
Date: (server clock)
Server: (Webserver name and version information)
Additional headers can be configured for example Cache-Control, it all depends on your language (PHP, CGI, Java, htaccess) and webserver (Apache, etc).
<?php header("Access-Control-Allow-Origin: http://example.com"); ?>
This command disables only first console warning info
Result: console result
If you use Java and spring MVC you just need to add the following annotation to your method returning your page :
@CrossOrigin(origins = "*")
"*" is to allow your page to be accessible from anywhere. See https://developer.mozilla.org/fr/docs/Web/HTTP/Headers/Access-Control-Allow-Origin for more details about that.
There are 3 ways to allow cross domain origin (excluding jsonp):
1) Set the header in the page directly using a templating language like PHP. Keep in mind there can be no HTML before your header or it will fail.
<?php header("Access-Control-Allow-Origin: http://example.com"); ?>
2) Modify the server configuration file (apache.conf) and add this line. Note that "*" represents allow all. Some systems might also need the credential set. In general allow all access is a security risk and should be avoided:
Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Credentials true
3) To allow multiple domains on Apache web servers add the following to your config file
<IfModule mod_headers.c>
SetEnvIf Origin "http(s)?://(www\.)?(example.org|example.com)$" AccessControlAllowOrigin=$0$1
Header add Access-Control-Allow-Origin %{AccessControlAllowOrigin}e env=AccessControlAllowOrigin
Header set Access-Control-Allow-Credentials true
</IfModule>
4) For development use only hack your browser and allow unlimited CORS using the Chrome Allow-Control-Allow-Origin extension
5) Disable CORS in Chrome: Quit Chrome completely. Open a terminal and execute the following. Just be cautious you are disabling web security:
open -a Google\ Chrome --args --disable-web-security --user-data-dir
Source: Stackoverflow.com