What is Hibernate

Hibernate is popular open source object relational mapping tool for Java platform. It provides powerful, ultra-high performance object/relational persistence and query service for Java. Hibernate lets you develop persistent classes following common Java idiom - including association, inheritance, polymorphism, composition and the Java collections framework. Hibernate lets you develop persistent classes following common Java idiom - including association, inheritance, polymorphism, composition and the Java collections framework.
Hibernate takes care of the mapping from Java classes to database tables and also provides data query and retrieval facilities. Hibernate significantly reduces development time in the software projects.
Hibernate is an open source object/relational mapping tool for Java. Hibernate lets you develop persistent classes following common Java idiom - including association, inheritance, polymorphism, composition and the Java collections framework.
Hibernate not only takes care of the mapping from Java classes to database tables (and from Java data types to SQL data types), but also provides data query and retrieval facilities and can significantly reduce development time otherwise spent with manual data handling in SQL and JDBC.
Hibernates goal is to relieve the developer from 95 percent of common data persistence related programming tasks.
Hibernate is Free Software. The LGPL license is sufficiently flexible to allow the use of Hibernate in both open source and commercial projects (see the LicenseFAQ for details). Hibernate is available for download at http://www.hibernate.org/. This tutorial aims to provide insight into Hibernate version 3.0RC and its usage Some of the main features of hibernate are listed below and we have tried to explain some of them in detail later in this tutorial.
Transparent persistence without byte code processing
Transparent persistence
JavaBeans style properties are persisted
No build-time source or byte code generation / processing
Support for extensive subset of Java collections API
Collection instance management
Extensible type system
Constraint transparency
Automatic Dirty Checking
Detached object support
Object-oriented query language
Powerful object-oriented query language
Full support for polymorphic queries
New Criteria queries
Native SQL queries
Object / Relational mappings
Three different O/R mapping strategies
Multiple-objects to single-row mapping
Polymorphic associations
Bidirectional associations
Association filtering
Collections of basic types
Indexed collections
Composite Collection Elements
Lifecycle objects
Automatic primary key generation
Multiple synthetic key generation strategies
Support for application assigned identifiers
Support for composite keys
Object/Relational mapping definition
XML mapping documents
Human-readable format
XDoclet support
HDLCA (Hibernate Dual-Layer Cache Architecture)
Thread safeness
Non-blocking data access
Session level cache
Optional second-level cache
Optional query cache
Works well with others
High performance
Lazy initialization
Outer join fetching
Batch fetching
Support for optimistic locking with versioning/timestamping
Highly scalable architecture
High performance
No “special” database tables
SQL generated at system initialization time
(Optional) Internal connection pooling and PreparedStatement caching
J2EE integration
JMX support
Integration with J2EE architecture (optional)
New JCA support