Using ColdFusion to find the RSS URL from a web site

Many web sites now include a simple way to autodiscover the RSS feed for the site. This is done via a simple LINK tag and is supported by all the modern browsers. You should see - for example - a RSS icon in the address bar at this blog because I have the following HTML in my HEAD block:

<link rel="alternate" type="application/rss+xml" title="RSS" href="http://feedproxy.google.com/RaymondCamdensColdfusionBlog" />

I was talking to Todd Sharp today about how ColdFusion could look for this URL and I came up with the following snippet.

<cfset urls = ["http://www.raymondcamden.com", "http://www.coldfusionbloggers.org", "http://www.androidgator.com", "http://www.cfsilence.com/blog/client"]>


<cfloop index="u" array="#urls#">
<cfoutput>Checking #u#<br/></cfoutput>
&lt;cfhttp url="#u#"&gt;
&lt;cfset body = cfhttp.fileContent&gt;
&lt;cfset linkTags = reMatch("&lt;link[^&gt;]+type=""application/rss\+xml"".*?&gt;",body)&gt;
&lt;cfif arrayLen(linkTags)&gt;
    &lt;cfset rssLinks = []&gt;
    &lt;cfloop index="ru" array="#linkTags#"&gt;
        &lt;cfif findNoCase("href=", ru)&gt;
            &lt;cfset arrayAppend(rsslinks, rereplaceNoCase(ru,".*href=""(.*?)"".*", "\1"))&gt;
        &lt;/cfif&gt;
    &lt;/cfloop&gt;
	&lt;cfdump var="#rsslinks#" label="RSS Links"&gt;
&lt;cfelse&gt;
    None found.
&lt;/cfif&gt;
&lt;p/&gt;

</cfloop>

The snippet begins with a few sample URLs I used for testing. We then loop over each and perform a HTTP get. From this we can then use some regex to find link tags. You can have more than one so I create an array for my results and append to it the URLs I find within them. Nice and simple, right? You could also turn this into a simple UDF:

<cfscript> function getRSSUrl(u) { var h = new com.adobe.coldfusion.http(); h.setURL(arguments.u); h.setMethod("get"); h.setResolveURL(true); var result = h.send().getPrefix().fileContent; var rssLinks = []; var linkTags = reMatch("<link[^>]+type=""application/rss\+xml"".*?>",result);

if(arrayLen(linkTags)) {
    var rssLinks = [];
    for(var ru in linkTags) {
        if(findNoCase("href=", ru)) arrayAppend(rsslinks, rereplaceNoCase(ru,".*href=""(.*?)"".*", "\1"));
    }
}
return rssLinks;

} </cfscript>

Not sure how useful this is - but enjoy!

Raymond Camden

Using ColdFusion to find the RSS URL from a web site

About Raymond Camden

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