Hibernate tutorial

Hibernate is a powerful high-performance Object/Relational persistence and query service for Java applications. In Hibernate it maps object oriented classes to the database tables and also provides data query. It’s so simple and easy.

Before come to Hibernate, I’ll get some time to explain where it is come from.

There are some mismatches, when mapping object oriented classes and relational databases. Here we want to use a technique to map them correctly. So Object Relational Mapping here. Object Relational Mapping is used for avoid following mismatches between   object oriented classes and relational data bases.

There may be more classes than the number of corresponding tables in the data base. Relational data bases do not defined any similarity to inheritance which is main concept in OOP. RDBMS only has concept of sameness while OOP has object identity and object equality. RDBMS is used foreign key for association columns while OOP is used object reference. The method of access to object class and RDBMS is different.

For more clear, I’ll give you a example for class and data base table.

public class Student {

   private int id;

   private String name;

   private int telno;

   

   public Student() {}

   public Student(String name,int telno) {

      this.name = name;

      this.telno = telno;

   }

   public int getId() {

      return id;

   }

   public String getName() {

      return name;

   }

  

   public int getTelno() {

      return telno;

   }

}

Above program is Java student class and By creating a object we are going to store data in following table.

create table STUDENT (

   id INT NOT NULL auto_increment,

   name VARCHAR(30) default NULL,

   telno INT  default NULL,

   PRIMARY KEY (id)

);

There are some advantages over traditional JDBC (Java Data Base connectivity). There are no need to deal with data base implementation. It hides details of SQL queries from OO logic. Entities are based on business concepts rather than database structure. It is developed application faster.

There are many Java ORM Frameworks. Here we use Hibernate framework which provide services to store and retrieve objects from relational data base.

Hibernate exist between java objects and database server to handle object –relational mechanisms and patterns by mapping java classes to database tables and from java data types to SQL data types.

Hibernate supports RDBMS like MySQL, Oracle, HSQL Database Engine, DB2/NT, PostgreSQL, FrontBase, Microsoft SQL Server Database, Sybase SQL Server , Informix Dynamic Server and technologies like J2EE, Eclipse plug-ins, XDoclet Springand, Maven.