I just got back from the Denver
JUG meeting and have lots to talk about. I've started this post at 11:03
p.m., for the record. I want to start out with discusssing a topic that Dave
and I talked about a few days ago. Basically, in his Ag
application, he is using one Business Delegate and one DAO to do all his business
logic and data access. Actually, he's got two DAO's, one for Hibernate
and one for Castor. Basically, the DAO
is determined at startup, set on the Business Delegate and then stuffed into
the servlet context. While Ag is a small application, it got me thinking. I
believe the recommended pattern for this is to have a Business Delegate
for each entity, as well as a DAO. So for a user, you would end up with 4 classes,
UserManager/UserManagerImpl and UserDAO/UserDAOHibernate. So everytime I add
a new entity, i.e. account, I have to create 4 new classes. What a pain, and
a lot of copy and pasting - or at least that's how I'd do it.
Dave's KISS methodology at first
struck me as strange, but then I thought, "Damn, that's a lot easier."
So now in AppFuse (reference implementation: security-example),
I changed to use this idea - with a BusinessManager/BusinessManagerImpl and
ApplicationDAO/ApplicationDAOImpl. The idea is that these will contain any and
all methods to access data.
I went to the DJUG meeting still struggling this
this pattern, feeling like it stunk and I should back it out and go with a factory
pattern and a business delegate/dao for each entity. However, during Marc Fleury's
presentation, he preached that one of the founding rules of JBoss was KISS.
He said that the greatest thing about open source is that no one will ever even
look at your code until it's broken. "And how bad does it suck when you
have to look through 5 levels of inheritence to figure out the problem?"
He mentioned that bad code was his favorite, because chances are - if there's a bug
- it'll be staring you in the face, rather than buried inside some design
patterns and 10 different classes. I agree, so I'm going with KISS, but I'm also
interested in hearing your opinions. I like the current architecture of AppFuse
because it sets the business manager on startup, stores it in the servlet context
and is available for everyone to use at any time. There's nothing saying that
I couldn't set a SessionBean (on the business manager as it's proxy) and call
EJBs for my persistence layer.
In fact, after Marc's gospel about JBoss, I want
to use EJBs. In fact, not just EJBs, I want to use JBoss - and I can't wait
for "JB 4." Why? Well they're adding the ability to add all of EJB's
services (i.e. Security, Transactions, Persistence) to any
POJO. This means that all you need
to do is write a little deployment descriptor for it, and whalla, you're in
business. His sermon is something you really need to see to appreciate. I can't
do it justice in summarizing it here, but I certainly liked what he had to say,
and feel like I'm a better person for it. The JBoss Group's goal is to become the
de facto standard for application servers. I like their idea that the app server
should be free - and the money (usually spent on app servers) should be directed
towards smart developers instead. He also mentioned that JBoss Group (the company)
is doing great right now and will be spending some cash on Marketing and PR to squash
any rumors that it's not good enough.
Marc mentioned that most of the things he talked about tonight are written in his
Blue Paper (PDF, 11 pages), titled "Why I love EJBs".
It's part 1 of 3, the Blue of the "Red, White and Blue Technology Trilogy."
Other news that I stumbled upon today:
- JBoss uses JavaGroups,
and I've heard you can make work with Tomcat - for clustering and such.
- The release plan for Struts 1.1 Beta 3 has been committed to CVS, code freeze
this Saturday.
- Ted Husted defends
Struts after I posted it's recent
criticizm to the mailing list.
- The xPetstore Application
has a new release. xPetStore is a refactored version of Sun PetStore application
that shows how to use xDoclet to build WODRA (Write Once, Deploy and Run Anywhere)
J2EE application. Tested with JBoss and WebLogic.
Phew, done at 11:44 p.m.
Here's an interesting new extension for Struts:
The TVC Framework uses the Struts framework to create HTML tables with functionality that includes paging, sorting, filtering of data, and data validation.
This joins the ranks of Ed's <display:*> tag library and Yuriy's html table tag library. I've always like the display tag library as it's easy to setup and use - just pass it an ArrayList of beans and you're off! The TVC Framework seems to offer some cool functionality, but you have to pay $995 for the good stuff :(. Of course, if you're trying to code similar functionality on your own, you'd probably save your self some money if you bought it.
