Displaying an RSS Feed using ASP ~ ASP Coding Guide

This tutorial will walk you through adding dynamic content from an RSS 2.0 data feed. RSS is a XML format for syndicating news content, web site updates, and blogs. Learn how to add this content to your web site with ASP.

RSS 2.0 Format
The RSS 2.0 is a very simple XML format. In the RSS feed, the tag will repeat for news item. The following is a very simple example of an RSS feed. See the Resources below for complete RSS 2.0 specification.

<>channel title
link to channel
description
en-us

<em>item title</em>
link url
unique id
item description

Reading the RSS Feed
To read the RSS feed, the MSXML2.DOMDocument object is used to read and parse the XML. This object allows for the XML DOM (Document Object Model) to be easily accessed.

The following example read an RSS feed into the XML DOM object:

Set xmlDOM = Server.CreateObject("MSXML2.DOMDocument")xmlDOM.async = False
xmlDOM.setProperty "ServerHTTPRequest", TruexmlDOM.Load("http://www.codebeach.com/rss-it-jobs.asp")

Parse the news items
The information in the RSS feed that we are interested in is within the tags. To start, all of the items are placed in a list by calling the getElementsByTagName() method. Once we have the list of items, we will iterate over the list and get the data for each item in the feed.

'Get all of the  tags in the feedSet itemList = xmlDOM.getElementsByTagName("item")
strHTML = strHTML & ""
'Iterate over each itemFor Each item In itemList

  'Parse the item children
  For each child in item.childNodes
    Select case lcase(child.nodeName)
        case "title"
          title = child.text
        case "link"
          link = child.text
        case "description"
          description = child.text
    End Select
  Next

  'Build the HTML for each bullet item
  strHTML = strHTML & ""
  strHTML = strHTML & "& Server.HTMLEncode(link) & "'>"
  strHTML = strHTML & Server.HTMLEncode(title)
  strHTML = strHTML & ""
  strHTML = strHTML & "
"
  strHTML = strHTML & description
  strHTML = strHTML & "
 "
  strHTML = strHTML & "
"Next
strHTML = strHTML & "
"
Set xmlDOM = Nothing
Set itemList = Nothing
Response.Write(strHTML)

Final Version
Below is the complete version of the example to read the RSS 2.0 feed. The final version will also cache the HTML content built on the RSS feed. This is so it won't get the RSS feed everytime the web page is loaded. By caching the resulting HTML, it will improve the page performance and it won't overload the server that you are requesting the feed from. To view more information on caching, you may want to read the tutorial Caching Data in ASP.

<%@ Language="VBScript" %><html>
<head>
<title>RSS Reader</title>
</head>
<body><%If DateDiff("h", Application("rss-html-time"), Now()) >= 2 then

  Set xmlDOM = Server.CreateObject("MSXML2.DOMDocument")
  xmlDOM.async = False

  xmlDOM.setProperty "ServerHTTPRequest", True
  xmlDOM.Load("http://www.codebeach.com/rss-it-jobs.asp")

  'Get all of the  tags in the feed
  Set itemList = xmlDOM.getElementsByTagName("item")

  strHTML = strHTML & ""

  'Iterate over each item
  For Each item In itemList

    'Parse the item children
    For each child in item.childNodes
      Select case lcase(child.nodeName)
        case "title"
          title = child.text
        case "link"
          link = child.text
        case "description"
          description = child.text
      End Select
    Next

    'Build the HTML for each bullet item
    strHTML = strHTML & ""
    strHTML = strHTML & "& Server.HTMLEncode(link) & "'>"
    strHTML = strHTML & Server.HTMLEncode(title)strHTML = strHTML & ""
    strHTML = strHTML & "
"
    strHTML = strHTML & description
    strHTML = strHTML & "
 "
    strHTML = strHTML & "
"
  Next
  strHTML = strHTML & "
"

  Set xmlDOM = Nothing
  Set itemList = Nothing

  Application.Lock
    Application("rss-html") = strHTML
    Application("rss-html-time") = Now()
  Application.UnLockEnd If
Response.Write(Application("rss-html"))%></body>
</html>

ASP Coding Guide

Tuesday, February 13, 2007

Displaying an RSS Feed using ASP

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