<?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="hibernate.Product" table="products">
   <id name="productId" column="productId" >
   </id>

  <set name="parts">
     <key column = "productId" />
     <one-to-many class = "hibernate.Parts" />
  </set>
<property name = "productName" type = "string" />

</class>

</hibernate-mapping>

<?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="hibernate.Parts" table="parts">
    <id name="partId" column="partId" >
       <generator class="assigned"/>
     </id>
     <property name="partName" column="partName" />

  </class>
</hibernate-mapping>

package hibernate;

import java.util.HashSet;
import java.util.Set;

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

public class ProductAppln {
   public static void main(String[] args) {
       Session session = null;
       Transaction tx = null;
       Product product = null;
       Parts parts = null;
       try{
          SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
          session =sessionFactory.openSession();
          tx = session.beginTransaction();
          Set parts_set = new HashSet();
         parts = new Parts();
         parts.setPartId(1);
         parts.setPartName("screw");
         parts.setPartId(1);
         parts_set.add(parts);
         parts = new Parts();
         parts.setPartId(2);
         parts.setPartName("nuts");
         parts_set.add(parts);

         product = new Product();
         product.setProductId(1);
         product.setParts(parts_set);
         product.setProductName("Laptop");
         session.save(product);
         tx.commit();
       }catch(HibernateException e){
          e.printStackTrace();
       }
       catch(Exception e){
          e.printStackTrace();
       }finally{
          session.flush();
          session.close();
          System.exit(0);
       }
   }
}

<?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.connection.url">jdbc:oracle:thin:@localhost:1521:bob</property>
        <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
        <property name="hibernate.connection.username">scott</property>
        <property name="hibernate.connection.password">tiger</property>
        <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>
      <property name="show_sql">true</property>
      <property name="hibernate.hbm2ddl.auto">update</property>

        <mapping resource="Parts.hbm.xml" />
        <mapping resource="Product.hbm.xml" />

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

package hibernate;

import java.util.Set;

public class Product {
   private int productId;
   private String productName;
   private Set parts;      //One product can contain many parts
   
   public Set getParts() {
      return parts;
   }
   public void setParts(Set parts) {
      this.parts = parts;
   }
   public int getProductId() {
      return productId;
   }
   public void setProductId(int productId) {
      this.productId = productId;
   }
   public String getProductName() {
      return productName;
   }
   public void setProductName(String productName) {
      this.productName = productName;
   }
}

package hibernate;


public class Parts {
   private int partId;
   private String partName;
   
   public int getPartId() {
      return partId;
   }
   public void setPartId(int partId) {
      this.partId = partId;
   }
   public String getPartName() {
      return partName;
   }
   public void setPartName(String partName) {
      this.partName = partName;
   }
}

@Entity
@Table(name="DISTRITOS")
public class Distrito implements Serializable {
    // <editor-fold defaultstate="collapsed" desc=" PrimaryKey:   String id ">
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id_distrito", nullable=false)
    private Long id;
   
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    //</editor-fold>
   
    // <editor-fold defaultstate="collapsed" desc=" Property:   String nome ">
    @Column(name="nome_distrito", nullable=false, unique=true)
    private String nome;
    public String getNome() {
        return nome;
    }
    public void setNome(String nome) {
        this.nome = nome;
    }
    // </editor-fold>
   
    // <editor-fold defaultstate="collapsed" desc=" N-1  Relation to Pais pais ">
    @ManyToOne
    @JoinColumn(name="PAIS_FK", nullable=false)
    private Pais pais;
   
    public Pais getPais() {
        return this.pais;
    }
   
    public void setPais(Pais pais) {
        this.pais = pais;
    }
    // </editor-fold>
   
    // <editor-fold defaultstate="collapsed" desc=" 1-N  Relation to Collection /*Concelho*/ concelhos ">
    @OneToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE}, mappedBy="distrito")
    private List<Concelho> concelhos = new ArrayList<Concelho>();
   
    public List<Concelho> getConcelhos() {
        return this.concelhos;
    }
   
    public void setConcelhos(List<Concelho> concelhos) {
        this.concelhos = concelhos;
    }
   
    public void addConcelho(Concelho concelho){
        concelho.setDistrito(this);
        concelhos.add(concelho);
    }
    // </editor-fold>

    public String toString() {
        return getNome();
    }
}