Re: Java Accessors Are They Evil?

James Perkins skrev:

Hello All,
I realize this article is kind of old, but I found it interesting none the
less.
http://www.javaworld.com/javaworld/jw-09-2003/jw-0905-toolbox.html

I just can't figure out how you can get around getters and setters. I
understand it makes more sense to build a method to calculate a discount or
something like that, but what I don't understand is how you create an object
based on data from a database?

I think the title is badly chosen.

As far as I can see he is arguing for two things:

1) Methods should be declared to return _interfaces_, not classes. Then the methods creates an object of a class which implements the interface. The interface can remain unchanged, while the chosen class may be changed as needed.

Example: "public List getResults()" versus "public ArrayList getResults()".

The first one defines the return type to be an interface where any particular implemention may be chosen - ArrayList, SortedList, etc.. The caller doesn't care and doesn't need to know. The second one defines the return type to be an ArrayList, and nothing else will do (except a subclass). This is inflexible and freezes the ArrayList type in perpetuity.

2) Work should be done by the responsible object holding the necessary data, and not by pulling all the data out of the objects with getters in a method in a different object and setting the result back in a third object.

So you would not do something like.

invoice. setDeliveryCity(recipient.getCity());
invoice.setDeliveryZip(recipient.getZip());
....
but something like

invoice.setDeliveryAddress(recipient.getAddress())

where the setAddressFromRecipient method knows about the details of the invoice address, and knows how to get the address from a person.

The appropriate location is the object who knows the best (I cannot remember the pattern name for it :( ).


The database row can be reasonably handled as a Map. It is very tedious to build a custom class with getters and setters for each field (requires to build up a bytecode representation and get a classloader to create it) but it can be done.