All of the Hibernate and J2EE books that I've seen seem to recommend a layer of DAOs where each DAO has an add, update, delete and one or more query methods for a certain object type (i.e. business object) for a J2EE web application. Any reason not to make one set of add(), update() and delete() methods on a class named something like PersistenceManager that uses reflection to determine the business object type and perform the requested persistence operation rather than making a bunch of DAOs that just delegate to Hibernate for a specific object type?

granted, lots of methods in DAOs are cookie-cutter style. But there are lots of situations where you want to add functionality or hide implementation. Just like using setter / getter methods in your pojos and not accessing the attributes directly.

Example 1: You may want to fire an event every time you update an item that fullfills certain filter criteria.

Example 2: You want queries that hide implementation. you might want to make a query method like findPeopleIneedToFireToday(). The construction of the query would be well hidden from the developer using the DAO.

dirk