Hibernate : SessionFactory
In this section we will discuss concept of SessionFactory.
Hibernate SessionFactory :
For SessionFactory import org.hibernate.SessionFactory API.
SessionFactory is one of Hibernate concept. It creates session instances. In
general an application has a single SessionFactory.
It is immutable and when it is created its internal state is set. This internal
state contains metadata about O/R mapping.
The behavior of a sessionFactory is controlled by properties supplied at
configuration time.
SessionFactory is thread safe so that many threads can access SessionFactory and
request for sessions.
Example : Here we are going to give you example and describing how sessionFactory plays its role and how session is created.
Take a view on Hibernate.cfg.xml - Here we are configuring sessionFactory.
<?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> <!-- Database connection settings --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/hibernate_examples</property> <property name="connection.username">root</property> <property name="connection.password">root</property> <!-- JDBC connection pool (use the built-in) --> <property name="connection.pool_size">1</property> <!-- SQL dialect --> <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> <!-- Echo all executed SQL to stdout --> <property name="show_sql">true</property> <!-- Drop and re-create the database schema on startup --> <property name="hbm2ddl.auto">none</property> <mapping class="net.roseindia.table.Employee" /> </session-factory> </hibernate-configuration>
Main Class HibernateSessionFactory.java -Here we show how sessionFactory creates Session.
package net.roseindia.main;
import java.util.*;
import net.roseindia.util.HibernateUtil;
import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
public class HibernateSessionFactory {
public static void main(String[] args) {
SessionFactory sessionFactory = HibernateUtil.getSessionFactory(); //Creating instance of SessionFactory
Session session = sessionFactory.openSession(); // session is opened
String hql = "SELECT emp.name, emp.salary, emp.dateOfJoin from Employee emp";
Query query = session.createQuery(hql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List objectList = query.list();
Iterator iterator = objectList.iterator();
System.out.println("Employee Name \t Salary \t Date of Join");
while (iterator.hasNext()) {
Map map = (Map) iterator.next();
System.out.print(map.get("0"));
System.out.print("\t\t" + map.get("1"));
System.out.print("\t\t" + map.get("2"));
System.out.println();
}
session.close(); // session is closed
}
}
Output :
Hibernate: select employee0_.name as col_0_0_, employee0_.salary as col_1_0_, employee0_.date_of_join as col_2_0_ from employee employee0_ Employee Name Salary Date of Join Mandy 20000 2010-03-12 00:00:00.0 Som 20000 1999-06-22 00:00:00.0 Mac 15000 2003-12-23 00:00:00.0 Roxi 22000 2001-02-03 00:00:00.0 Rowdy 20000 2012-06-27 00:00:00.0 Linda 20000 2010-06-12 00:00:00.0 Lizza 25000 2010-06-12 00:00:00.0