Architecture Rituals and Patterns: On the Importance of tying up the cat - Part 1
The Zen master and his disciples began their evening meditation. The cat that lived in the monastery made so much noise that it distracted the monks from their practice, so the master ordered that the cat be tied up during the entire evening practice. When the master died years later, the cat continued to be tied up during the meditation session. And when, eventually, the cat died, another cat was brought to the monastery and was tied up during the practice sessions. Centuries later, scholars descendants of the Zen master wrote treatises on the profound spiritual meaning of tying up a cat for meditation practice.
A few years ago, I attended an event organized by Sun to promote Java here in Mexico (I think it was called Java Dev Days). At that time, I entered a presentation, I think it was by Sang Shin (the creator of JavaPassion), in which he explained how simple it was to use JRuby with Ruby on Rails to create a "hello world" page. It was something like this video: http://www.youtube.com/watch?v=sas3KCKwyHI. It was the first time I saw RoR, so on that side, it seemed educational... however, most of the audience... was falling asleep!
That caught my attention... why were they all so bored, from what I had been able to observe the previous days, many of them were enterprise programmers, with the kind of clients that I have had, who give you very little information to work with, demand a lot, and want everything for yesterday..., so I started to listen to the comments that they exchanged quietly (or not so quietly) between yawns:
Is that simple? It took like 15 minutes to make a hello world screen!
How boring, I could do that with JSP in 1 minute
Where does this guy get that this is simple? Did you see the mega directory structure that those commands created? That's not simple at all!
You can tell this presenter spends his time giving courses, but he's never worked in real life, I'd like to see him with his RoR having to get the job done at 3 in the morning
At least the 2 rows sitting in front of me were not remotely impressed with RoR. And why would they be if in JSP you can make a hello world simply by putting something like this:
<HTML>
<HEAD>
<TITLE>Hello World</TITLE>
</HEAD>
<BODY>
<H1><%= "Hello World!" %> </H1></BODY>
</HTML>
Certainly, arguing that the 15 minutes of the multi-step video are simpler than this is absurd.
Well, some will say, (as part of me thought) the point of the example with RoR is not to show how simple it is to make a silly "Hello World" but to show the potential of RoR's MVC architecture to do much more complex things...
Let me see if I understood... are you telling me that I'm going to complicate my life by making something easy much more difficult and that's going to result in a simplification of the difficult? More complexity today == Less complexity tomorrow? That violates YAGNI. (Yagni means: You aren't going to need it)
And it's not that you have to avoid violating YAGNI just to follow tradition, as in the case of the cat in the monastery. Yagni has a reason for being: in systems development, change is the only constant, and if you get ahead and build something before you have a clear idea of whether you really need it, when you get to the point where you are really going to use it, it is very likely that what you really need will be very different from what you had predicted. This doesn't mean that your code shouldn't be flexible, but you have to be very careful, because you can end up with an over-engineered solution, ready for situations that will never occur. If you use too much energy today, fighting with the ghosts of things that will never come, when the real enemies finally arrive, you won't have the strength to face them.
Now, one of the big problems we have in learning programming is that when we are learning, we have to build examples like a Hello World in RoR to understand how it works. But as instructors, we have to be very careful in saying "look, with this example I'm going to show you how simple this is...". No. You don't make a hello world in RoR because it's simple. Let's not confuse our students. We don't go to the gym to sweat because it's less tiring than staying at home watching TV. We go because by doing so we will improve our skills, we go to prepare ourselves for future situations. So, in programming, not only Yagni rules, we also have another principle: OAOO. (OAOO means, once and only once).
OAOO is the root cause of the apparent complexity of RoR, and the archenemy of copy&paste. OAOO has other names, it is also known as the DRY principle (Do not repeat yourself). It's not good to have copies of the same code scattered throughout the project, because if there is a bug in one of them, and you didn't follow OAOO, you'll have to find and fix them all, instead of solving the problem in one place.
OAOO and YAGNI are like Yin and Yang. They balance each other. Without OAOO, YAGNI would slowly strangle us. With OAOO, you always have a system that you can improve (a phrase by Ron Jeffries).
OAOO alone would also kill us, leading us to an eternal refactoring of code searching for the holy grail of the generic code with the fewest possible lines without ever stopping...
We need both. We need balance.
How many times have you faced code like this in your work:
DAO:
public List<Product> getProductList() {
logger.info("Getting products!");
List<Product> products = getSimpleJdbcTemplate().query(
"select id, description, price from products",
new ProductMapper());
return products;
}
Service:
public List<Product> getListOfProducts() {
logger.info("Getting products!");
List<Product> products = getProductsDao().getProductList()
return products;
}
Controller:
public List<Product> getProductsToList() {
logger.info("Getting products!");
List<Product> products = getProductsServices().getListOfProducts()
return products;
}
What value does this add? Why can't we simply do it like this (no Service layer, no DAOs layer):
Controller:
public List<Product> getProductsToList() {
logger.info("Getting products!");
List<Product> products = getSimpleJdbcTemplate().query(
"select id, description, price from products",
new ProductMapper());
return products;
}
Why is it that if you don't tie up the cat before meditating... I mean, why is it that the principles of multi-layer architecture dictate that it should be done this way... really? Is that really the answer? NO!
If it doesn't satisfy an immediate need and doesn't help OAOO (obviously the redundancy in this doesn't help OAOO), we shouldn't do it. We are burning precious time and energy on "busy work" that nobody will thank us for.
Heresy! Many have told me when I tell them to stop having so many layers just because. Layers are NECESSARY. You can't remove them.
Of course, you can, and I'm not the only one who thinks so. JBoss Seam was designed precisely with the idea of eliminating so much unnecessary layering. And that was YEARS ago. Why hasn't it dawned on most people that making layers for the sake of making layers is not correct? Why do we still tie up the cat and buy a new cat every time we start a new project? Tradition.
Now, traditions are not all bad, (those cultures with traditions that don't help their survival simply become extinct). Where does the idea come from that putting so many layers helps in any way?
I will talk about that in my next post in this series...
(originally published in spanish on Javamexico)
