Components like DAO, service locator, business delegate, filter, helper, and so on are design strategies.
They are translated to
java classes, obviously, but are components that exists only for a design strategy.
so i think that they're best suited to show in a component diagram.
In a class diagram you've to draw primarly the business classes.
GiUsEpPe (SCJP, SCWCD, SCBCD, IBM OOAD, SCEA/OCMJEA 5)