Introduction to hibernate framework

Before understanding the hibernation framework, we need to understand the Object Relational Mapping (ORM).

What is ORM?

ORM is a programming method to assign objects in java with the relational entities in the database. In this, entities / classes refer to the table in the database, the class instance refers to the rows and attributes of class instances refers to the table column in the database This provides solutions to problems that arise during the process of developing persistence applications using the traditional JDBC method. This also reduces the code that needs to be saved.

Need for tools like hibernate:

The main advantage of ORM like hibernate is that it shields developers from messy SQL. Apart from this, ORM provides following benefits:

Improved productivity:

§  High-level object-oriented API

§  Less Java code to write

§  No SQL to write

Improved performance:

§  Sophisticated caching

§  Lazy loading

§  Eager loading

Improved maintainability:

§  A lot less code to write

Improved portability:

§  ORM framework generates database-specific SQL for you

What is hibernate?

Hibernate is a relational object mapping (ORM) and a persistence structure that allows you to assign simple old Java objects to relational database tables. The main objective of hibernate is to free the developer from common tasks related to data persistence. the objects in the java with the tables in the database very efficiently and also you can get the most out of using your facilities of consultation and data recovery. Mainly using Hibernate in your projects, you can save incredible time and effort.

Architecture of hibernate :

Following is a detailed view of the Hibernate Application Architecture with few important core classes.

The Hibernate architecture is placed in layers to keep it isolated from having to know the underlying APIs. Hibernate is like a bridge between the Java application and the relational database.

Session interface:

This is the main interface used by hibernation applications. Instances of this interface are slight and are not expensive to create and destroy. Hibernation sessions are not secure threads. It allows you to create query objects to retrieve persistent objects. It refers to the JDBC Factory for Transaction connection. It contains a mandatory cache (first level) of persistent objects, which is used when navigating the object graphic or searching for objects by identifier.

Session session=SessionFactory.openConnection();

SessionFactory Interface:

This is a factory that delivers session objects to hibernate the application. It is a heavy object, so there will usually be a single SessionFactory for the entire application and it is shared among all sub-processes of the application. SessionFactory caches generate SQL statements and other metadata mapping that Hibernate uses at runtime. It also stores cached data that has been read in a unit of work and can be reused in a future unit of work.

  Configuration configuration=new Configuration();

  configuration.configure();

  ServiceRegistry sr= new ServiceRegistryBuilder().applySettings(configuration.ge    tProperties()).buildServiceRegistry();

  SessionFactory sf=configuration.buildSessionFactory(sr);

SessionFactory object is created with the help of configuration object.

Configuration Interface :

This is used to configure hibernate. It’s also used to bootstrap hibernate. Mapping documents of hibernate are located using this interface.

Transaction Interface :

This is an optional interface but the above three interfaces are mandatory in each and every application. This interface abstracts the code from any kind of transaction implementations such as JDBC transaction, JTA transaction.

Query and Criteria Interface :

This interface allows the user to perform queries and also control the flow of the query execution.

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