public static void main(String args[]){
       // Session session=HibernateUtil.getSessionFactory().getCurrentSession();
        SessionFactory sessionFactory = new Configuration().configure() .buildSessionFactory();
        Auto a=new Auto(4,"renault","19",1991);
        Auto b=new Auto(5,"fiat","punto ",1999);
        Auto c=new Auto(6,"fiat","barchetta ",2000);
        ArrayList<Auto> au=new ArrayList<Auto>();
        au.add(b);
        au.add(a);
        au.add(c);
        Iterator<Auto> it;
        it=au.iterator();
        Session session;
        while(it.hasNext()){
            session =sessionFactory.openSession();
            session.beginTransaction();
        session.save(it.next());
        //session.flush();
        session.getTransaction().commit();
        }

public class Auto {

    private int id;
    private String marca;
    private String modello;
    private int anno;
    private ArrayList<Parte> componenti;

    public Auto () {
    }

    public Auto (int id,String marca,String modello,int anno) {

        this.id=id;
        this.anno=anno;
        this.marca=marca;
        this.modello=modello;

    }

    public int getAnno () {
        return anno;
    }

    public void setAnno (int val) {
        this.anno = val;
    }

   
    public ArrayList<Parte> getComponenti () {
        return componenti;
    }

public void setComponenti() (ArrayList<Parte> val) {
        this.componenti = val;
    }

   
    public String getMarca () {
        return marca;
    }

    public void setMarca (String val) {
        this.marca = val;
    }

    public String getModello () {
        return modello;
    }

    public void setModello (String val) {
        this.modello = val;
    }
}

<?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>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost/Catalogo</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">123</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="hibernate.hbm2ddl.auto">create</property>
    <mapping resource="Auto.hbm.xml"/>
  </session-factory>
</hibernate-configuration>