What is Hibernate ?

Hibernate is a persistent service.
It works with various databases such as Oracle, MySQL, Sybase,
SAP DB, IBM DB2, MS SQL Server, Postgre SQL.
Hibernate may be used in standalone application and web applications.
Hibernate has to be configured before use.
The table should have a primary key.

First read and understand about Object Relational Mismatch.

Steps in using Hibernate.

01. Reading configuration files
02. Creating SessionFactory
03. Creating Sessions
04. Application specific code

Different layers.

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Application
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Session
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Session Factory
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Configuration
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Configuration files
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In hibernate3 the configuration file is called hibernate.cfg.xml.
The primary purpose of this file is to configure the Hibernate service.

There are 3 methods by which database connection details are intimated
to Hibernate service.

01. Provided by Hibernate framework in the configuration file.
02. Provided by JNDI datasource in case if you are using J2EE server.
03. Database connection details given by the user.

01. User defined configuration.
   
    Hibernate configuration file has only dialect and resource mapping.

    con = cfg.openSession();

02. Uses database configuration given by configuration file.
    This is used in case of standalone applications and non managed environment.

    5 properties

    dialect
    driver
    url
    username
    password

    resource mapping

03. Uses Hibernate with JNDI datasource.

    This type of configuration is used with application servers.
   

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