Hibernate Basics

Introduction
Example

It is a framework developed by Red Hat.
Hibernate is an open source, lightweight, ORM (Object Relational Mapping) tool.
An ORM tool simplifies the data creation, data manipulation and data access. It is a programming technique that maps the object to the data stored in the database.
The ORM tool internally uses the JDBC API to interact with the database.

Hibernate is slower than JDBC but development is faster in Hibernate.

Hibernate is suitable for database migration e.g. from Oracle to MySQL.
For database migration it uses Dialect.

Let’s create simple client.java in which we will access table from MySQL using Hibernate.

Required things:

Jars – Hibernate Jars
Files –
1. Student.java (POJO/form bean)
2. Client.java
3. hibernate.cfg.xml
‘Student’ table in database.

Student.java –

It is POJO/form bean class.
It contains all the column names of table Student and its getters and setters.
It is not compulsory to have same names as column names because we have mapped with the help of annotation @Column.

hibernate.cfg.xml –

It is one file for single project.
It contain all hbm paths.
The configuration file contains all the informations for the database such as connection_url, driver_class, username, password etc.

Jbkstudent table -

CREATE TABLE `jbkstudent` (
  `sid` int NOT NULL,
  `firstname` varchar(45) DEFAULT NULL,
  `lastname` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`sid`)
);

Jbkstudent.java –

package com.javabykiran.hibernate;
// Generated Feb 24, 2020 6:23:34 PM by Hibernate Tools 5.2.12.Final

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

/**
 * Jbkstudent generated by hbm2java
 */
@Entity
@Table(name = "jbkstudent")
public class Jbkstudent implements java.io.Serializable {

    private int sid;
    private String firstname;
    private String lastname;

    public Jbkstudent() {
    }

    public Jbkstudent(int sid) {
	this.sid = sid;
    }

    public Jbkstudent(int sid, String firstname, String lastname) {
	this.sid = sid;
	this.firstname = firstname;
	this.lastname = lastname;
    }

    @Id
    @Column(name = "sid", unique = true, nullable = false)
    public int getSid() {
	return this.sid;
    }

    public void setSid(int sid) {
	this.sid = sid;
    }

    @Column(name = "firstname", length = 45)
    public String getFirstname() {
	return this.firstname;
    }

    public void setFirstname(String firstname) {
	this.firstname = firstname;
    }

    @Column(name = "lastname", length = 45)
    public String getLastname() {
	return this.lastname;
    }

    public void setLastname(String lastname) {
	this.lastname = lastname;
    }
}

Hibernate.cfg.xml –

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	  "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
	<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
	<property name="hibernate.connection.password">root</property>
	<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/jbkhibernate</property>
	<property name="hibernate.connection.username">root</property>
	<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
	<property name="show_sql">true</property>
    </session-factory>
</hibernate-configuration>

JbkClient.java

package com.javabykiran.hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class JbkClient {
    public static void main(String[] args) {

	Configuration cfg = new Configuration();
	cfg.configure().addAnnotatedClass(Jbkstudent.class);

	// creating SessionFactory Object
	SessionFactory sf = cfg.buildSessionFactory();

	// creating Session Object
	Session session = sf.openSession();

	// Fetching data from table
	Jbkstudent stu = session.load(Jbkstudent.class, 1);
	System.out.println(stu.getSid() + " " + stu.getFirstname() + " " + stu.getLastname());

	// Insert data into table
	session.beginTransaction();
	Jbkstudent jbk = new Jbkstudent(2, "JavaByKiran", "JavaByKiran");
	session.save(jbk);
        session.getTransaction().commit();
    }
}


    Output:
     Hibernate: select jbkstudent0_.sid as sid1_0_0_, jbkstudent0_.firstname as firstnam2_0_0_, jbkstudent0_.lastname as lastname3_0_0_ from jbkhibernate.jbkstudent jbkstudent0_ where jbkstudent0_.sid=?
     1 JavaByKiran JavaByKiran
     Hibernate: insert into jbkhibernate.jbkstudent (firstname, lastname, sid) values (?, ?, ?)

Hibernate Basics

Hibernate Introduction

Hibernate Example