Is there any way to inform web site has been changed?one way is get all web page contex and compare it with previous contex!but Im looking for solution that notify web page changes without get page context!
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The only way that you could tell a website had changed without accessing the content is for the website to notify you itself, through an API or RSS feed or similar mechanism.
Widor
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Unless the site in question has a mechanism to actively notify you...
You don't necessarily need to get all site content, but you do need to make a request to the site. You can make a HEAD request to get only the headers. Depending on the site, these headers may contain information about when it was last modified.
Additionally, you can check for a response of 304 Not Modified if you have content cached. This is more often seen with a HEAD request than a GET request, but can be used either way. Like with any request, of course, it depends on how the server decides to respond.
You can look up the standards easily enough, and how you make use of these options depends on what technology you use. But basically a HEAD request is simply asking the server, "Don't send me the page, just send me some basic information about the page." And checking for a 304 response is basically asking the server, "This is when I last accessed this resource, has anything changed?"
David
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