Question

I have a JAVA class in which I have implemented parsing of XML using the DOM parser. The XML file that is parsed is a configuration file which has configuration params. Any request coming to my website will be redirected based on the information that is returned from this xml file. I have 2 questions around this

1) I would like to do the file parsing only once and not every time. Since, DOM parser loads the xml into memory after the first time I would like to know how to check if the file is already available in the memory? so that the following is not called everytime

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new File(sFpath));

2) If the xml file changes how do I make sure the new chaged xml file is re-loaded.

Thanks,

Answer 1

The DOM is an intermediate format – parse it in some application-specific (and friendly) object structure, and stash that in a singleton. You don’t want to go hunting through a DOM for every web request. Then, regularly (every x minutes or y web requests), check whether the file has been updated, re-parse it, and update your singleton.