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Hibernate is an object-relational
mapping (ORM) solution for the Java language:
it provides an easy to use framework for mapping
an object-oriented domain model to a traditional
relational database. Its purpose is to relieve
the developer from a significant amount of relational
data persistence-related programming tasks.
Hibernate is free as open source software
that is distributed under the GNU Lesser General
Public License.
Hibernate's primary feature is mapping
from Java classes to database tables (and from
Java data types to SQL data types). Hibernate
also provides data query and retrieval facilities.
Hibernate generates the SQL calls and relieves
the developer from manual result set handling
and object conversion, keeping the application
portable to all SQL databases, with database portability
delivered at very little performance overhead.
Hibernate provides transparent persistence
for Plain Old Java Objects (POJOs). The only strict
requirement for a persistent class is a no-argument
constructor, not compulsorily public. (Proper
behavior in some applications also requires special
attention to the equals() and hashCode() methods.)
Hibernate can be used both in standalone
Java applications and in Java EE applications
using servlets or EJB session beans.
EJB Vs Hibernate
The similarity is that with both you
can persist a class in a DB; but it ends there.
Period.
EJBs are supposed to be components, in the sense
that they're not just one class, but a set of
classes, descriptors (thats an XML and/or annotations
in EJB 3) and usage and management contracts.
All of this in order to allow a container (JBoss,
Weblogic, etc.) to provide services to those components,
and to be able to reuse and distribute this components.
This services are, among others, transactions,
concurrent access control, security, instance
pooling, etcetera.
Hibernate is "just" an ORM (Object/Relational
Mapping) tool. Quick and dirty, this means you
can store an object tree belonging to an class
hierarchy in a relational DB without writing a
single SQL query. But no transaction control,
no instance pooling, no concurrency control, and
certainly no security.
On the other hand, inheritance and polymorphism
are IMPOSSIBLE out of the box with EJB. A quite
big drawback.
The big issue seems to be this days that there's
no intersection between Hibernate and EJB's funcionality.
What you can with one you can barely do with the
other. So EJB 3 is on its way to fill this gap
and solve all of our problems. The spec is a draft
for the time being, but there are some implementations,
already.
That's the difference between Hibernate and EJB,
in a nutshell.
NHibernate is an Object-relational
mapping (ORM) solution for the Microsoft .NET
platform: it provides an easy to use framework
for mapping an object-oriented domain model to
a traditional relational database. Its purpose
is to relieve the developer from a significant
amount of relational data persistence-related
programming tasks.
NHibernate
NHibernate is free as open source
software that is distributed under the GNU Lesser
General Public License.
NHibernate is a port of the popular
Java O/R mapper Hibernate to .NET. Version 1.0
mirrors the feature set of Hibernate 2.1, adding
a number of features from Hibernate 3. NHibernate
1.2.0, released May of 2007, introduces many more
features from Hibernate 3 and support for .NET
2.0, stored procedures, generics and nullable
types. NHibernate 2.0 is currently under development
and will provide most of Hibernate 3 features.
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