Question

I’m writing a program with a bunch of classes that will be serialized to save in a database and to be sent through a network.

To make things easier for accessing the class properties via command line interface, I’m considering storing the properties in a Map class, instead of giving each property it’s own variable.

Basically, instead of using something like this:

String id = account.getUserId();

I would do this

String id = account.properties.get("userId");

Is this an advisable way to do things?

Answer 1

Yes, it’s a pretty sensible model. It’s sometimes called the “prototype object model” and is very similar to how you would work in JavaScript where every object is effectively a Map. This in turn has led to the very popular JSON serialisation format.

Nice features:

• You don’t have to worry about messy inheritance heirarchies – you can just alter the properties at will.
• You can create a new object just by copying from another object (the prototype)
• Code to manipulate the data can do so in a uniform way, without having to explicitly name all the variables.
• It’s more “dynamic” compared to a static class definition – it’s easy to extend and modify your objects

Potential risks / downsides:

• You need to keep track of your property names if you use Strings – the compiler won’t do it for you! This issue can be alleviated by using Enums as keys, but then you lose some flexibility…
• You don’t get the benefits of static type checking, so you may find that you need to write more JUnit tests as a result to ensure things are working properly
• There is a slight performance overhead (though probably not enough to worry about, as map lookups are very fast)

I actually wrote an entire game in the 90s using a variant og this object model (Tyrant) and it worked very well.

Rather than having a Map object exposed however, you may want to consider encapsulating this functionality so that you can use an accessor method on the object itself, e.g.

String id = account.getProperty("userId");