Re: Examples of Pojo Free Code?

There's nothing about the ORM that forces them to use data classes. The
framework typically requires you to follow some conventions and/or
configure some options so that it knows how to match types. Also, you
typically have to provide a no-arg constructor so that it can instantiate
objects for you. Otherwise, they call them "plain old java objects" for a
reason. They can and should have behavior.

My advice would be the same as for any heavy framework use:

1) YAGNI?
2) Test-drive a wrapper around the framework APIs you intend to use so that
you can reference them directly in only a couple of places. It blows my
mind why more people don't do this.
3) Use a gradual changeover or parallel change strategy to move current
uses of the framework to the new wrapper. This could take months or years
to fully complete depending on how large and complex the legacy code is.
Prioritize new functionality and/or areas that have caused you difficulty
in the past.

Beyond that, it sounds like there is a interesting cultural/educational
problem. I would want to investigate to understand why they believe
something that is clearly false: ORMs force them to write poorly factored
and/or non-OO code. This is simply not the case. For example, Industrial
Logic uses Hibernate in their eLearning product code (written in Java) and
there are plenty examples of well factored classes in there.

I have also run into a tendency to:

 a) copy contrived examples from the ORM documentation that needlessly
couple you to the framework then blame the framework.

b) misinterpret some design book as suggesting these are ORM "best
practices." For example, Domain Driven Design, by Eric Evans, seems to be
misinterpreted as saying that persistent "Entities" are just data and
"Services" operate on that data. He describes both of these patterns but
never says that they should be implemented that way.

If you convince yourself that all the behavior belongs in static services
(libraries) and all the data belongs in data classes (structs) then you
should really be writing in C. That's not a knock on C. I love C. Java was
designed for a different paradigm, though, and if you are going to work
with it professionally you should know what that is.


On Fri, Apr 11, 2014 at 10:50 AM, Mark Levison <[email protected]> wrote:

>
>
> I'm running an Agile Development course with some wonderful people at a
> client who're addicted to their existing ORM. We've been discussing the
> evil involved in Data Classes (i.e. classes with no behaviour). In their
> world the habit of creating data classes comes from the fact that their ORM
> (Hibernate and JPA) creates POJO type objects and they manipulate them.
> They get the problem but would live to see an example of project that
> doesn't do this.
>
> Do you know an OpenSource project that doesn't a use POJOs to get its data
> in/out of an RDBMS? Do you know an ORM that helps people avoid creating
> Data Classes?
>
> BTW I'm asking on this list lacking a better place.
>
> Cheers
> Mark
>
>
> --
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