I didn't experiment this feature in NetBeans 6.9 but according to the release notes (and to Bug 178108), my understanding is that this is supposed to work out of the box if you are using EclipseLink (and if you add eclipselink-jpa-modelgen.jar
to the classpath):
Creation of new persistence unit was
simplified in all wizard, in Entity
From Database wizard the most suitable
persistence unit will be created by
default.
Now metamodel classes will be
generated for project entities if
persistence unit will be created with
eclipselink provider (supported in
j2se, web, ejb and application client
projects). Automatic processor
addition is temporary disabled because
of an issue in eclipselink, you can
add eclipselink-jpa-modelgen jar from
eclipselink distribution to your
project manually to enable metamodel
generation.
The entity from DB wizard was enhanced
to allow regeneration. It allows user
to regenerate the entity from scratch
after structural DB change or update
the entity class by adding the code
for the new DB fields.
For other persistence providers, did you actually try to add their metamodel generator JAR and to declare the annotation processor as suggested in part I and part II of the link you provided?
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