[GSoC09] Hibernate + Devcathlon

Premise:
This past weekend I had the chance to dive into implementing Devcathlon's database back-end (Derby) by using Hibernate. I, unfortunately ran into some issues while applying these changes. They seem very pin-pointed since changes were recently made using Hibernate, but there were other confounding factors that hindered a smooth application. After last week's implementation, I was sure that the issue seemed small and easily doable. However the common, 1001 timeout error (which occurs during a Devcathlon's call out to Hackystat's SensorBaseClient) proved to be more of a challenge than I thought. In this entry I'll describe the issues I ran into, and the many solutions leading up to resolving this problem. I'll also mention about next week's goals and a timeline for Devcathlon's first milestone deliverable.

What was the issue?
SensorBaseClient 1001 timeout error - This happens due to the increase complexity of the application and heavy call loads out to Hackystat's SensorBaseClient server. This occurred while running the JUnit test cases against recent modifications while applying Hibernate. Another possible problem may arise due to the increase size of the application, which causes an overload memory usage on the contained JVM's heap size.

Resolving the issue:
I went through dismantling many of the previous code implementations. It wasn't awful, though I felt that changing the current state of the application was too obtrusive. I was prone to just keeping my changes reserved to just my additions. Any modifications to the actual code base would need to be reasonably thought out. So the (temporary) remedy for this matter happened to reside in modifying the DevcathlonTestHelper class. The error mostly occurs while trying to make multiple calls out to the SensorBase, along with calling out to Hibernate. The calls to Hibernate happens to stall (exactly at the same spots) and the connection to the SensorBaseClient apparently times out. I tried various ways to remedy the problem, a few of which that were clearly suggested by Johnson in this videocasting. If you ever run into this error, I would suggest to first watch that video and try out each solution, if all else fails then it's safe to assume that the problem must be you! The work around was applied yesterday, and I was thrilled that the build finally passed verify. The code has been unloaded to SVN and I would like some kind of code review from my mentors.
Changes for this past week.
r903 & r904

Next week's work load:
Just a reiteration, the primary goal at this point is to clearly implement a DB for Devcathlon. Considering how much I've endured this past week, It'll hopefully support a faster development time, now identifying those issues. Along with finishing the database, I will get the ball rolling next week for the user interface.
The first delivery date will be within two weeks from now, which will include a solid database implementation using Hibernate (with all/any kinks worked out), UI improvements mentioned in earlier blog posts and suggestions made by peers, and finally a mailing system using JavaMail. Look out for the official beta release of Devcathlon v2.0 on July 6, 2009.