Why doesn't Hibernate have a mapping GUI?
Because you don't need one. The Hibernate mapping format was designed to be edited by hand; Hibernate mappings are both extremely terse and readable. Sometimes, particularly for casual / new users, GUI tools can be nice. But most of the time they slow you down. Therefore, Hibernate let's you make the decision about your development process. We offer easy to write XML mapping metadata, XDoclet annotations, JDK 5.0 Annotations for the JSR-220 (EJB3) Persistence API, and a toolset available for the Eclipse IDE with editors, wizards, code generation, and reverse-engineering features.
Just read this from "http://www.hibernate.org/16.html#A8". Hum... I disagree with this. Can give you a comparation with a generator, middlegen, it has an interface, very basic and simple, that alows the developers to specify the name of the class and it's attributes. Very simple to use and it is only necessary to edit it one time. If the data base is changed it's much esier to edit the changes visualy then by code (in a configuration file).
We should be using the computers and not the other way around... Why complicate when the it can be very simple?