How to get previous URL?

I need the URL from wh开发者_JS百科ich my web app is called. For eg:- If there is a link to my site foo.com from stackoverflow.com, I need the stackoverflow link in web app(managed bean).

All helps appreciated, thanks.

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Not always filled, but you can use:

HttpServletRequest.getHeader("Referer");

Note: The spelling error is on purpose. For an explanation see here.

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By checking the HTTP Referrer you can see from which site the request for your site originated.