Question

How should one go about filtering a series of domain objects according to user-defined criteria? Should the filtering methods be in the model or should they be in the DAO?

Answer 1

If you want to use your model objects only (mainly) as data containers you should put the filter into the DAOs you are already using. It is a good practice to make sure, that the user defined criteria are database independent (so pass your own filter object instead of plain e.g. Hibernate Criteria. query by example may work great, too).

Then your DAO methods can look like this:

public interface BeanDao
{
    List<Bean> findAllByFilter(BeanFilter filter);
}