Hibernate is lovely… it needs a little more attention to set up but once that’s done no other persistence framework will beat it. So let’s go over the setup steps here. I know there is a lot of information (good job on that from hibernate, springs lacks this at the moment) on this topic online, still it would be nice to have an overview (so I can get back to this summary myself).

dependencies

Let it be clear that using hibernate means you’ll need to add some dependencies, jar files, to your project. If you use maven to manage these depencies this can’t be hard.

your model

You’ll need some POJO’s or Plain Old Java Objects you want to store. These are simple Java objects with a ctor, some private properties and public setters and getters, also called JavaBeans.

mapping

Next you need to let hibernate know how these POJO’s need to be stored in whatever JDBC enabled db you want to use. Therefore create a mapping file for all your POJO’s. I use the following one as a reference, it comes from the hibernate reference documentation (see sources). Also make sure you check the mapping cheat sheet (sources) for more advanced mapping files.

<!DOCTYPE hibernate-mapping PUBLIC
      "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">



        <class name="Cat" 
            table="cats"
            discriminator-value="C">
                
                
                        
                

                <discriminator column="subclass" 
                     type="character"/>

                

                <property name="birthdate"
                    type="date" 
                    not-null="true" 
                    update="false"/>

                <property name="color"
                    type="eg.types.ColorUserType"
                    not-null="true"
                    update="false"/>

                <property name="sex"
                    not-null="true" 
                    update="false"/>

                <property name="litterId"
                    column="litterId"
                    update="false"/>

                <many-to-one name="mother"
                    column="mother_id"
                    update="false"/>

                <set name="kittens"
                    inverse="true"
                    order-by="litter_id">
                        
                        
                

                <subclass name="DomesticCat"
                    discriminator-value="D">

                        <property name="name" 
                            type="string"/>

                

        

        
                
        

configuration

Then you can already configure hibernate. Create an xml file called hibernat.cfg.xml in your project resources folder and copy the following, adjusted for your needs, into it.

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">



    

        
        org.hsqldb.jdbcDriver
        jdbc:hsqldb:hsql://localhost
        sa
        

        
        1

        
        org.hibernate.dialect.HSQLDialect

        
        thread

        
        org.hibernate.cache.NoCacheProvider

        
        true

        
        create

        

    

Check the hibernate reference documentation (sources) for more information on this config. Good to know is that the jdbc driver and sql dialect depend on the database you are using. Als the mapping resources at the bottom here need to point towards your mapping files you created earlier.

some util

You can use the following util code to access the hibernate session.

package util;

import org.hibernate.*;
import org.hibernate.cfg.*;

public class HibernateUtil {

    private static final SessionFactory sessionFactory;

    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

}

hit it

Now you can start writing your services. In these services you retrieve the hibernate session, begin and commit transactions and in between this you’ll saveOrUpdate, load, delete, list, … your POJO’s. For more specific queries you’ll need to get into hql.

    Session session = HibernateUtil.getSessionFactory().getCurrentSession();
    session.beginTransaction();

    Person aPerson = (Person) session.load(Person.class, personId);

    // The getEmailAddresses() might trigger a lazy load of the collection
    aPerson.getEmailAddresses().add(emailAddress);

    session.getTransaction().commit();

sources:
o hibernate reference documentation
o hibernate mapping cheat sheet
o hibernate tutorial, quick start