I ran into the need to change a project I am working on from keeping a ton of java objects in the air due to real-time calculations and performance.  Didn’t need (or want) full database that would need to be maintained by a database group.

Every time the application was restarted, the entire thing would be reloaded based on other sources (other databases of data — all different db’s, data and transformation needed).  The transformation requires each base source to have different set of transformations and calculations performed on them.  Also since the sources have different real-time intervals there needed to be different levels or transformation going on.

Of course if I was a dba, I would be saying this should all be done in some huge db iron and storing it into some jumbo sized tables and all could be done with scripts, triggers, etc.  But I am not a dba, I like my logic in code, not a database.  That is just who I am.  I love Java and like to see what my code is doing to the data and db are used to store and get things for me, period.   Just wasn’t going down that road.  We can agree to disagree or not.

Ruled out in like 5 seconds that the use of flat files to store the calculated data would just not work.  I had to have the ability to retrieve the data fast (wanted hash maps or trees in memory, but that quickly ran out of steam due to quantity of data).  I also wanted to keep everything in the single app (single deployed war) at the end of the day.  Makes support easier in the long run.  One point to look at instead of 12!

So I came up with a list of what I wanted:

1. Needed to be quick.
2. Needed to be embeddable (not an Oracle, MySQL or anything like that) / memory friendly.
3. Needed to deploy when the web application deployed (all self contained).
4. Needed it to be support by ORM (Apache Cayenne) since already using in the project for other db work.
5. Needed to be open source.
6. Needed to be temporary, last only while web app was up and running and throw everything away when app restarted.

I had narrowed my list down to three choices I was entertaining (your experience might be different):

• Apache Derby aka Sun Java DB
• HSQLDB
• H2

They probably would all get the job down.  But I tried to narrow it down by my criteria by doing a little reading (Google + reviews + blogs + groups complaining about stuff + did I like what I saw):

1. Started reading, it appeared H2, then Derby (latest) and then HSQLDB was the speed arrangement. (YMMV)
2. More reading… All would meet the need, but H2 had some really nice instant up and running features that I liked. (IMO)
3. Same as #2, they all would meet the need more or less.  Just different feature set, but once again H2 was drawing my attention. (IMO)
4. All had native support in Cayenne since I am using 3.0 (H2 was not supported prior to 3.0, but that didn’t matter since I am using 3.0).
5. All met this need and would of been fine.
6. All met this need in some fashion and would of been fine as well.

So it really came down to how easy “did it appear” for me to get this started, embedded and actually working, using it in actual live code all in the same day.  For me it had to be H2.

There were quite a few reasons other than meeting my 6 requirements above.  I also liked that it had an active change log which every month appeared to have forward progress and making the project better.  Open source projects are either constantly evolving and or dead.  Get worried when a project hasn’t had commits or quite a bit of progress in months, 6 months, last year, etc.  Code is never perfect, it can always be better.  Don’t leave it there to just die.

I have to admit that venturing down the H2 path in the first day of use has turned out to be a great choice.

Love the embedded console you get by including 1 (one, yes one) jar in your project which you were going to do anyways since that is the only lib required.  Edit your apps web.xml and bang.  That is supporting your dev project front and back.  I can see it will come in handy trouble shooting the application both during development and even possibly productional since we are talking ever changing live data.

Integrated really quickly with Cayenne.  I have cayenne actually building the schema from its own XML each and every time the app starts up.  Talk about reuse and single place for describing the model.  ORM creates the model, creates the Java classes and now builds me my schema in my temp db.  That is a win, win, win situation folks.  No SQL monkey business, period!

With a little more code (I mean little) I have it dropping everything (entire schema) and db temp files when it shuts down (all through a single listener config in the web.xml).  I love when things are simple and just work.   Kudos to Thomas for creating such a great db that works right out of the gate.  Simplest Java library I think I have ever used.

I plan to write up some of the things I find interesting in the coming month or two (along with some other Wicket and Cayenne stuff I have mocked up, but not typed into here).   Here are some of those ideas I have already worked through turned out beautifully (eluded to above)!

• DB embedded in app config.
• Cayenne used to build H2 schema.
• Purge db on shutdown.
• Performance / usage.

It should be noted that H2 is developed by Thomas Mueller who was the creator of HSQLDB (H2 can be seen as HSQLDB2, just better and it even said that it could merge back into HSQLDB)… anyhow.

H2 +1 in my book.

Well, I finally had to bite the bullet and migrate a large Wicket project from 1.3 to 1.4.  I was really not looking forward to it because of all the generic mess and model changes.

This was nothing against the Apache Wicket team, since they do an incredible job on the BEST Java framework ever (it is more than that.. but that is further down).

I just thought of having to review so much code and updating the ever growing set of Wicket “component” libraries, but that was the actual reason for the surge of change.

Some of the key sub projects I was leveraging were all converted (for sometime now) and were really starting to not go back to their 1.3x branches to update the older code.  I saw the 1.3x branches dying.  NO!!!!

I was trying to keep some of my key sub component / libraries manually synced from their newer bigger brother 1.4 code trees, but that was getting ever increasing painful and foolish.  Not to mention to find bug issues fixed in the 1.4 branches, but not in the 1.3x code base I was using.   So the decision was to maintain old branches for the sub projects (not my code even) or update my project and use all new 1.4 code for everything.

Jump… 1.4            1.4 is a very good great thing.

I know in the Wicket community there has been some huge Generic battles and long, long, long threads on it was the wrong approach, too verbose, too much code for no bang, blah, blah, blah. It was painful to watch since last year (thankfully they took it out of the forum and gave it a wiki home for folks to die over).

I actually find so far that 9 out of 10 times, it has made my code more understandable and actually working with models even more concise.  You get the added benefit of types collisions be detected in your IDE (if you use a real one) / compile time on models in the code that you would not get until you actually put the wrong object in a model for a component… then crash and burn and do a wtf was I thinking!  Nothing beats detecting issues before ever running a line of code.  I have C (not ++ or #, C) flashbacks of trying to figure out what code didn’t work, but would compile.  Boy I am glad I don’t code in that world anymore.

I am glad though, that I did hold out past the 1.4M3 period.  Much of the early on back and forth over how to implement generics was not pretty and I could only think of moving code from M1, M2 to M3, to RC…   Even sweet utility classes (albiet small classes) like ListModel and MapModel really do ease the coding and sets up the enhanced model design even better.   Once again, it makes the code more understandable as to what the Model contains and what you are working on.

Of course with any cleaning, updating has spurred on some good old refactoring of my own to leverage some new efforts in 1.4 branch and even how I plan to continue to leverage Apache Cayenne in some more elegant base Model designs of my own.  Should help with the whole deteaching and seperation level between Cayenne and Detachable models in Wicket so much cleaner.

So the dread, regret and final excitement was all part of my 1.4 migration.  At this point all projects will of course be 1.4x and some day 1.5… (Ajax enhancements could be even more awesome to come.)

Once again, it just goes to show that Wicket never steers me wrong and increases my I love for the whole framework project (99.9% of the time) that much better.  It makes Java Web development fun and exciting.  Come on kids, drink the cool aid, it won’t hurt ya!

SIDENOTE:

Wicket is not just a web framework, but a Java web way of life.   I don’t how many times I have told the story of that I will not / never (never say never right) go back to doing JSP development period.  It is just wrong once you see the light.

The Apache Wicket team is proud to present the second release candidate of Apache Wicket 1.4. This is the first Wicket version with java 1.5 as minimum requirement.

1.4 is really starting to shape up and since the whole generic movement in the project has settled since M3 days, I am going to have to jump from 1.3 to 1.4 big brother.

Wicket is the only way!

The Wicket team has officially released 1.3 RC2. Things are really shaping up and it sounds like RC3 should be final hopefully.

With the exception of the example “look” update, the API is frozen and stability is exception. I would expect final release coming by the end of the year (purely my guess).

You can go check out the details at: Wicket 1.3.0 RC2 Details

You can get your download at one of the Apache Download Mirrors: http://www.apache.org/dyn/closer.cgi/wicket/1.3.0-rc2

The Wicket team has officially released 1.3 RC1.  I personally have been 1.3 beta / source tree for months and have to say that it has been stable even during this time of finding and fixing bugs.

This release is the first in a series of release candidates until we feel confident to finalize Wicket 1.3. This is called a release candidate because we strive for API freeze. This means only bug fixes will be done on the 1.3 release from now on.

The API freeze should help speed along the final release so they can start working towards 1.4 and some new functionality that has been on hold to get 1.3 out the door.

You can go check out the details at: Wicket 1.3.0 RC1 Details