I noticed that several domain classes in the CaveatEmptor source have a
private Date created = new Date(); member that is used only in the equal() / hashCode() method.

For example the Category class has this member defined. Is the sole purpose of this to be easily be able to implement equals() for this class since implementing equals() for the Category class without the 'created' member would be rather involved and would require to compare parent categories recursively?

If this member was added only to be easily implement equals()/hashCode(), is this a pattern you recommend in cases where computing the business equality would turn out to be complicated or expensive? The overhead of this method obviously being an extra non-business 'created' field in the database table.

Thanks,
Sanjiv

LOL, no, it is there because the date something is created is an interesting item of data to keep in the database.

It's actually both: I wanted to show that in practice and real applications you have almost always entity attributes like "created", "created by" and other meta data. This is a often a good choice for the equals() implementation.

An equals() implementation for a plain Category would be involved, but again, a class with a single attribute is unrealistic in the real world.