Once i was looking for a nice RSS class/component for ASP which allows me to read all kind of feed formats programmatically. In addition to the correct parsing it should also be able to create own feeds for publishing purposes. Unfortunately I could not find any component which fits those requirements in ASP and therefore written my own.
Due to the different versions of RSS (0.91, 0.92, 1.0, 2.0, etc.) and formats like ATOM it was not really easy to parse them all within one component. I needed to find the least common denominator which consists of the basic elements like feed title, feed description, feed published date, the feeds language and it published items. The items on the other hand must hold at least title, description, category, author, link and published date. This metadata is available but its occurrence is a bit different in e.g. ATOM and RSS. The component I have written consists of two VBScript classes (RSS and RSSItem) which supports the following features (download and documentation is at the bottom):

• Reading all kind of RSS formats (RSS 0.91, 0.92, 0.94, 1.0, 2.0 and ATOM)
• Generating own feeds as RSS 2.0 (with UTF8)
• Generation can be done directly into a file
• XSLT can be applied to the feed
• Feeds can be cached for a given amount of time (all visitors share the same cache).
• Timeout for the request can be configured. (if server not responding, etc.)
• Supports the simple Dublin Core elements (http://www.dublincore.org/)
• easy to use programmers interface

Before I keep going with the examples of how to use the class(es) here is a link to a demo I have quickly created on my ASP server. Play around and check if your feeds are being correctly recognized by the component.

RSS reader DEMO

Could the component parse your feed? If not please let me know so I can improve it. However, lets check how we use this tool. The following example creates an instance of the RSS class, requests the feed and loads all its information into the class' properties. The title of the feed is written to the response:

Interesting thing here is the failed property. Whenever a feed is requested it is necessary to check the failed property if the request has failed or not. If it failed it means that the feed could not be recognized as a valid (supported) feed, the server is not responding, the url does not exist, or the XML could not be parsed (and therefore is invalid). As we are requesting data from a kind of "untrusted" source it is a nice feature to display our user that the feed is currently not available. If the load was a success all properties are populated with the feeds data. Iterating through the items of the previous example looks the following:

Those lines iterate through the items (items is a dictionary which holds objects of type RSSItem). Nice feature here is that the date has already been converted into a VBScript date type and can be used within all date functions. In this example the month of the date is written out.
With this concept it is easily possible to request feeds and process them programmatically. E.g. storing them into the database, etc.

Using the cache

Caching can be turned on with the "setCache" method which requires the type of interval and the interval value (in the example 1 hour). This feed is stored now within the cache (see Caching class for ASP) on the server for 1 hour before it is requested again. All users share the same cache which means that only the first user will recognize the request and the others will already get it from the cache. The RSS class supports caching but it requires the Cache class for this feature. Just download it and include it like in the example.

Using XSLT for the feed

If you have your own XSL file for your feeds you can apply it with the draw() method. It grabs the feed, applies the given stylesheet and prints out the result to the response. As you can see there is again this check for the failed property. That is necessary because the same errors as with the load() method could happen. Additionally the transformations could have failed. It is also possible to use caching here, just as described before.

Generating an own feed (RSS 2.0)

This example generate a simple feed with one item. As you can see its necessary to use the RSSItem class. The generate() method generates a feed into a file called rss.xml. The method also returns the generated xmldom if you prefer to store the feed in a different way. E.g. you could output directly to the response with:

Another example for the generation grabs an existing feed (in this case ATOM) and generates an RSS 2.0 version. Its somehow a tranformation which is therefore possible .. a nice side effect.

There is nothing to say more now :) Have fun with this component and feel free to use it. Just keep my credits ... I am looking forward to any enhancements from you guys and to the feedback. I am not an expert on feeds and therefore you might have some suggestions, improvements, etc.

Greetings from vienna.

Download RSS 1.0
RSS 1.0 Documentation
DEMO

NOTE: RSS class is part of the ajaxed library now!
check ajaxed library for a newer version...

(9 votes, average: 4.33 out of 5)

 Loading ...

This entry was posted on Sunday, July 1st, 2007 at 9:51 pm and is filed under classic ASP (VBScript). You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.