Sometimes when using using an XML Data Source from a URL, you need to pass in a parameter which is used in the URL.  Take for example an RSS Feed that gives you top news stories for a company based on their ticker symbol.  The attached example uses a Report Parameter to gather the ticker symbol and updates the data source URL in the data source's beforeOpen event using the following code:

filelist = this.getExtensionProperty("FILELIST");
filelisturl = filelist.substring(0,filelist.indexOf("=")+1);
this.setExtensionProperty("FILELIST", filelisturl + params["TickerSymbol"]);

View Live Report

The report design is also attached to this posting if you would like to download it.

This report was designed in BIRT 2.2.2.