If your servlet is not responding to web request, it shouldn't be a servlet. Use a ServletContextListener instead. For making your object perform tasks at given intervals look at either java.util.Timer or, if you need more functionality look at the Quartz library.
Another approach is to go with a servlet, put the lookup code in doGet or doPost, and trigger it with a web request using wget and a cronjob. This keeps you from having to spawn your own threads in a web app.
Please enter your question in a new thread. Adding to the bottom of someone else's is called hi-jacking and not a nice thing to do. It has a tendency to derail the conversation about the original poster's question.