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Find a Broken Link - Coldfusion

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In our day to day coding, how many times have we come across a necessity to check whether a URL is a broken link or not?

For those of you that answered countless and are using ColdFusion like myself, then this article is for you.  It will show you how to accomplish this task programmatically within your CFML-based web application.


The Code
<cffunction name="urlExists" output="no" returntype="boolean">
    <!--- Accepts a URL --->
    <cfargument name="urlval" type="string" required="yes">
 
    <!--- Initialize result to FALSE unless returns valid status --->
    <cfset var result=false>
 
    <!--- Attempt to retrieve the URL with method head  to get only the header info in response --->
    <cfhttp url="#arguments.urlval#" method="head" resolveurl="no"  timeout="1000" />
 
    <!--- Check That a Status Code is Returned --->
    <cfif isDefined("cfhttp.responseheader.status_code")>
        <cfif cfhttp.responseheader.status_code NEQ "404">
            <!--- If NOT 404, return TRUE --->
            <cfset result=true>
        </cfif>
    </cfif>
 
    <cfreturn result>
</cffunction>

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The function requires that the developer passes in a URL as a parameter and then returns a boolean flag indicating the existence of the specified URL.

For improved performance, the function hits the url using CFHTTP and HEAD method to get only the header status code as a response, rather than retrieving all the page information which we would using GET method.  Thus the process becomes much faster.


The Usage
<!--- set a variable like chkurl to any URL. --->
<cfset chkurl = "http://your.url.here" />

<!--- calling the function urlExists and passing the chkurl value to the function within a cfif conditional --->
<cfif not urlExists(chkurl)>
    <!--- broken link, display alternate information. --->
<cfelse>
    <!--- link valid, continue processing requiring the checked URL. --->
</cfif>

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As simple as that!

And you can even put this function in a ColdFusion Component (CFC), allowing it to be used in any application you want.


The Need
But why would we even want to use this in an application?

Well, just consider the power of the CFHTTP tag utilized above.  It can be used to create a portal page that presents data from other portions of your intranet for example.  

Consider now on this page, you show information from each of five departments, who have their own web page.  What if one of their pages was no longer valid/down?  

With this neat new function, you will be able to determine in code, quickly, if a link is broken and display an error or alternate content that is more appropriate to your page design.

Moreover, since this is done dynamically, if that URL ever becomes valid again, then your code doesn't need to be changed.  The other condition will now be executed as the link is no longer broken.


Hope you found this helpful and it serves you well!


For more information on CFHTTP tag:
http://livedocs.adobe.com/coldfusion/6.1/htmldocs/tags-p58.htm
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