Database connection not closed in Destroy() method of servlet

Question

Hi,
I have a problem with my deployed web application. At first, I thought Glassfish was messing up on me, and after checking the log I could see plenty of null pointer exceptions being thrown at lines in my code where I generate prepared statements from my connection object. I have been initialising my connection in the Init() method of all my classes, and equally, I've been closing it in Destroy(). I can only imagine that destroy() isn't being called - since the log clearly shows "connection success" messages but not "connection closed" messages. I am connecting to the servlets via a J2ME app on my mobile phone. Does connecting in this way somehow not invoke the destroy method when the servlets work is complete? Am I going to need to move all my connection initilisation and closing into the necessary doGet/doPost methods of each of my servlets?
Chris

Answer 1

You shouldn't be keeping the connection that long open. It's a bad design. It will timeout sooner or later and your complete application will crash. Always acquire and close the connection in the shortest possible scope, preferably just in the same method block where you process the query and/or results. If you want to improve performance while connecting, consider using a connection pool.
Back to the actual problem: a servlet is created only once during application's lifetime and not during every request as you appears to think.
You may find this tutorial useful to read on about using the DAO pattern in JSP/Servlet.
[http://balusc.blogspot.com/2008/07/dao-tutorial-use-in-jspservlet.html]