Getting The Requested URL From The Page Request Object (Servlet) Without Using CGI

Posted November 1, 2006 at 8:22 AM

Tags: ColdFusion

Traditionally, I figure out which page URL has been requested by recreating it from various CGI variables:

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As you can see, it takes into account CGI.https, CGI.http_host, CGI.script_name, and CGI.query_string. This works totally fine for me. But, I have been told that relying on CGI variables is not a good way to go because every server handles CGI data differently. In another blog post, Dan G. Switzer, II made this comment:

Also, custom header information can be applied by custom filters run within the web server--which is why the CGI scope was designed to return an empty string if the key isn't explicitly defined. One reason I don't rely on the cgi.script_name is that not all web servers return it. I really try to avoid using the CGI scope when at all possible.

Frankly, the idea of not using the CGI scope was a bit scary. How could I figure out the URL? Turns out, you can get it directly from the Request servlet object that is available through the ColdFusion page context:

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The GetRequestUrl() returns a string buffer which is why the we call ".ToString()" on the GetRequestUrl() return value; this converts the string buffer to a simple string. Before we convert the url buffer to a string, though, we append the query string to it. As you can see, the query string is also available through the request object. That's all there is to it.

Now getting the requested URL is CGI-agnostic. But, how does the request servlet object know what the URL and query string values are? Frankly, that's not my concern. That's the whole beauty behind black-boxing data retrieval - I don't need to know the implementation of it, I just need to know that it returns the correct values.

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Reader Comments

what is the other methods beside GetRequestUrl() ?

Ben, Nice job. I see more and more of your postings lately... frankly I just don't know how you find the time ;)

Patrick, It looks like you can get more information on the methods available from: http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/http/HttpServletRequest.html

Although the version of the SDK might be different, it's a good starting point.

Joshua,

Thanks for posting that link. I was hoping around all over the place looking at different online documentation. The one ColdFusion using is something ColdFusion-specific ( I think ), but it most likely extends this class.

As far as time... I WISH i had more. I get about 5.5 hours of sleep a night, which helps but I could certainly use a few more hours in the day :(

Thank you!!!!!!
most of the time when I search something on the internet it takes time to figure out what I need....with this all I had to do is copy and paste....sooooooo simple.....Thanks!

Thank you!!!!!!
most of the time when I search something on the internet it takes time to figure out what I need....with this all I had to do is copy and paste....sooooooo simple.....Thanks!

Susan,

No problem! Please let me know if you ever get in a jam. More than happy to help.

Thanks for the code. I've been looking for a way to do this for a while now. Much appreciated!

Good man Ben.

Other methods using CGI don't work well.

Aside: How do you keep up the pace - everytime I good something ColdFusion related you have it covered. :)

@Topper,

I have a very active mind. The more I program, the more problems I need to solve :)

I tried using this for a CF custom 404 page and instead of returning the URL that occasioned the 404 error it returned the URL of the 404 page itself (even though that is not what is displayed in the browser)! Currently I am using CGI.query_string in order to return the errant URL but this solution is definitely not portable.

Thank you so much for this. I was spending a long time beating my head against a wall trying to figure out how to simply grab the entire URL with parameters!

What about url like this?

http://www.mydomain.com/index.cfm#fragmentid

Isn't there a way to just return the entire URL intact rather than trying to piece it back together?

Thank you for this code - it's so much harder to find this stuff for ColdFusion than it is for Apache!

I'm trying to force www., and here's what my final code is:
<code>
<cfif (CGI.SERVER_NAME EQ "example.net")>
<cfset strUrl = CGI.script_name & "?" & CGI.query_string />
<cfheader statuscode="301" statustext="Moved permanently">
<cfheader name="Location" value="http://www.example.net#strUrl#">
</cfif>
</code>

Thanks again!

Thanks Ben, very useful.

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