Byron Kiourtzoglou

About Byron Kiourtzoglou

Byron is a master software engineer working in the IT and Telecom domains. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

Persist object with Hibernate

This is an example of how to persist an object with Hibernate. To persist an object with Hibernate  we have set the example below:

  • In PersistOjectWithHibernate we use the Hibernate API to make the interface with the database.
  • We create a new Configuration, that allows the application to specify properties and mapping documents to be used when creating a SessionFactory. Usually an application will create a single Configuration, build a single instance of SessionFactory and then instantiate Sessions in threads servicing client requests.
  • Using configure() API method we use the mappings and properties specified in an application resource named hibernate.cfg.xml. Then, with buildSessionFactory() we instantiate a new SessionFactory, using the properties and mappings in this configuration. The SessionFactory will be immutable, so changes made to the Configuration after building the SessionFactory will not affect it. 
  • Use the getCurrentSession() API method to obtain the current session.
  • Use the beginTransaction() API method to begin a unit of work and return the associated Transaction object. If a new underlying transaction is required, begin the transaction. Otherwise continue the new work in the context of the existing underlying transaction.
  • Create a new object, here a new Employee object and use save(Object object) API method of Session to persist the given transient instance to the database.
  • Use getTransaction() API method of Session and commit() API method of Transaction to commit the Transaction.

In the code snippets that follow, you can see  the PersistOjectWithHibernate Class that applies all above steps. You can also take a look at the hibernate.cfg.xml file, that holds all configuration for Hibernate, such as JDBC connection settings, and employee.hbm.xml file that holds the mapping configuration between the Employee object and the Employee table. 

package com.javacodegeeks.snippets.enterprise;

import java.util.Date;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class PersistOjectWithHibernate {
	
	private static SessionFactory sessionFactory;
	
	public static void main(String[] args) {
		
		sessionFactory = new Configuration().configure().buildSessionFactory();
		
		Session session = sessionFactory.getCurrentSession();
		
		Employee employee = new Employee();
		employee.setName("Jack");
		employee.setSurname("Thomson");
		employee.setTitle("QA Engineer");
		employee.setCreated(new Date());
		
		try {
			session.beginTransaction();
			session.save(employee);
			session.getTransaction().commit();
		}
		catch (HibernateException e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}
		
	}

}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

  "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

  "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

  
<hibernate-configuration>
    <session-factory>

  <!-- JDBC connection settings -->

  <property name="connection.driver_class">com.mysql.jdbc.Driver</property>

  <property name="connection.url">jdbc:mysql://localhost/companydb</property>

  <property name="connection.username">jcg</property>

  <property name="connection.password">jcg</property>

  

  <!-- JDBC connection pool, use Hibernate internal connection pool -->

  <property name="connection.pool_size">5</property>


  <!-- Defines the SQL dialect used in Hiberante's application -->

  <property name="dialect">org.hibernate.dialect.MySQLDialect</property>


  <!-- Enable Hibernate's automatic session context management -->

  <property name="current_session_context_class">thread</property>


  <!-- Disable the second-level cache  -->

  <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>


  <!-- Display and format all executed SQL to stdout -->

  <property name="show_sql">true</property>

  <property name="format_sql">true</property>


  <!-- Drop and re-create the database schema on startup -->

  <property name="hbm2ddl.auto">update</property>

  

  <!-- Mapping to hibernate mapping files -->

  <mapping resource="Employee.hbm.xml" />

  
    </session-factory>
    
</hibernate-configuration>

Employee.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

  
<hibernate-mapping>

    <class name="com.javacodegeeks.snippets.enterprise.Employee" table="employee">

  <id name="id" column="id">


<generator class="native"/>

  </id>

  <property name="name" not-null="true" length="50" />

  <property name="surname" not-null="true" length="50" />

  <property name="title" length="50" />

  <property name="created" type="timestamp" />
    </class>
    
</hibernate-mapping>
CREATE TABLE `companydb`.`employee` (
  `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(45) NOT NULL,
  `surname` VARCHAR(45) NOT NULL,
  `title` VARCHAR(45) NOT NULL,
  `created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
);

Output:

Hibernate: 
    insert 
    into

  employee

  (name, surname, title, created) 
    values

  (?, ?, ?, ?)

 
This was an example of how to persist an object with Hibernate.

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