[Engine-devel] Simplifying our POJOs

[Mike Kolesnik]

Hi, 

Today many POJO s are used throughout the system to convey data: 

    • Parameters - To send data to commands. 
    • Business Entities - To transfer data in the parameters & to/from the DB. 

These POJOs are (usually) very verbose and full of boilerplate code . 

This, in turn, reduces their readability and maintainability for a couple of reasons (that I can think of): 

    • It's hard to know what does what: 


        • Who participates in equals/hashCode? 
        • What fields are printed in toString? 
    • 
Consistency is problematic: 

        • A field may be part of equals but not hashCode, or vice versa. 
        • This breaks the Object.hashCode() contract! 
    • 
Adding/Removing fields take more time since you need to synchronize the change to all boilerplate methods. 

        • Again, we're facing the consistency problem. 
    • 
These simple classes tend to be very long and not very readable.     • Boilerplate code makes it harder to find out which methods don't behave the default way. 
    • Javadoc, if existent, is usually meaningless (but you might see some banal documentation that doesn't add any real value). 
    • Our existing classes are not up to standard! 

So what can be done to remedy the situation? 

We could, of course, try to simplify the classes as much as we can and maybe address some of the issues. 
This won't alleviate the boilerplate code problem altogether, though. 

We could write annotations to do some of the things for us automatically. 
The easiest approach would be runtime-based, and would hinder performance. 
This also means we need to maintain this "infrastructure" and all the implications of such a decision. 


Luckily, there is a much easier solution: Someone else already did it! 

Check out Project Lombok: http://projectlombok.org 
What Lombok gives us, among some other things, is a way to greatly simplify our POJOs by using annotations to get the boilerplate code automatically generated. 
This means we get the benefit of annotations which would simplify the code a whole lot, while not imposing a performance cost (since the boilerplate code is generated during compilation). 
However, it's also possible to create the methods yourself if you want them to behave differently. 
Outside the POJO itself, you would see it as you would always see it. 

So what are the downsides to this approach? 

    • First of all, Lombok provides also some other capabilities which I'm not sure are required/wanted at this time. 


        • That's why I propose we use it for commons project, and make use of it's POJO-related annotations ONLY. 
    • 
There might be a problem debugging the code since it's auto-generated. 

        • I think this is rather negligible, since usually you don't debug POJOs anyway. 
    • 
There might be a problem if the auto-generated code throws an Exception. 

        • As before, I'm rather sure this is an edge-case which we usually won't hit (if at all). 

Even given these possible downsides, I think that we would benefit greatly if we would introduce this library. 

If you have any questions, you're welcome to study out the project site which has very thorough documentation: http://projectlombok.org 

Your thoughts on the matter? 


Regards, 
Mike 

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