Introduction To Orm World

Hibernate is a free, open source for Java designed to map objects to an RDBMS and to implement the object-oriented programming concepts in a relational database. It was started in 2001 by Gavin King as an alternative to EJB2 style entity bean. Hibernate ORM enables developers to more easily write applications whose data outlives the application process. As an Object/Relational Mapping (ORM) framework, Hibernate is concerned with data persistence as it applies to relational databases.

Why Hibernate?
To overcome the disadvantages of JDBC hibernate is preferable, So that programmer can focus more on business logic than manipulation of queries. Hibernate mainly solves the object-relational impedance mismatch problems that arise when a relational database is connected by an application written in an object-oriented programming language style. Object-relational impedance mismatches arise due to data type differences, manipulative differences, transactional differences, and structural and integrity differences. JDBC does not provide support for OOP concepts but by using Hibernate we achieve that.

Hibernate application mainly contain two files:

1)Configuration
The configuration file contains information about the database and mapping file. Conventionally, its name should be hibernate.cfg.xml.
2)Mapping
Hibernate itself maps Java classes to database tables using XML or by using annotations. The mapping file name conventionally, should be class_name.hbm.xml.

Hibernate Provides simple APIs for storing and retrieving Java objects directly to and from the database. If there is change in the database or in any table, then you need to change the XML file properties only. Abstracts away the unfamiliar SQL types and provides a way to work around familiar Java Objects. Hibernate does not require an application server to operate. Manipulates Complex associations of objects of your database. Minimizes database access with smart fetching strategies. Provides simple querying of dat