public class User {

    /** Attributs */

    private Integer id;

    private String pseudo;

    private String telephone;

    private String email;

    @XmlTransient
    private Set<Demande> demandes;

    @XmlTransient
    private Set<Invitation> aInvite;

    @XmlTransient
    private Set<Notification> notifications;

    private DernierePosition dernierePosition;

    @XmlTransient
    private Set<Group> groups;

    @XmlTransient
    private Set<Group> proprietaire;

    @XmlTransient
    private Set<Marqueur> marqueurs;

    /** Constructeur */
    public User() {
    }

    public User(String telephone, String pseudo, String email) {
        super();
        this.pseudo = pseudo;
        this.telephone = telephone;
        this.email = email;
        this.demandes = new HashSet<Demande>();
        this.aInvite = new HashSet<Invitation>();
        this.notifications = new HashSet<Notification>();
        this.groups = new HashSet<Group>();
        this.proprietaire = new HashSet<Group>();
    }

    public Integer getId() {
        return id;
    }

    @XmlElement
    public void setId(Integer id) {
        this.id = id;
    }

    public String getPseudo() {
        return pseudo;
    }

    @XmlElement
    public void setPseudo(String pseudo) {
        this.pseudo = pseudo;
    }

    public String getTelephone() {
        return telephone;
    }

    @XmlElement
    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public String getEmail() {
        return email;
    }

    @XmlElement
    public void setEmail(String email) {
        this.email = email;
    }

    @XmlTransient
    public Set<Demande> getDemandes() {
        return demandes;
    }

    public void setDemandes(Set<Demande> demandes) {
        this.demandes = demandes;
    }

    public DernierePosition getDernierePosition() {
        return dernierePosition;
    }

    @XmlElement
    public void setDernierePosition(DernierePosition dernierePosition) {
        this.dernierePosition = dernierePosition;
    }

    @XmlTransient
    public Set<Group> getProprietaire() {
        return proprietaire;
    }

    public void setProprietaire(Set<Group> proprietaire) {
        this.proprietaire = proprietaire;
    }

    @XmlTransient
    public Set<Notification> getNotifications() {
        return notifications;
    }

    public void setNotifications(Set<Notification> notifications) {
        this.notifications = notifications;
    }

    @XmlTransient
    public Set<Group> getGroups() {
        return groups;
    }

    public void setGroups(Set<Group> groups) {
        this.groups = groups;
    }

    @XmlTransient
    public Set<Invitation> getaInvite() {
        return aInvite;
    }

    public void setaInvite(Set<Invitation> aInvite) {
        this.aInvite = aInvite;
    }

    public void addToGroups(Group group) {
        this.getGroups().add(group);
        group.getInvites().add(this);
    }

    public void removeFromGroups(Group group) {
        this.getGroups().remove(group);
        group.getInvites().remove(this);
    }

    @XmlTransient
    public Set<Marqueur> getMarqueurs() {
        return marqueurs;
    }

    public void setMarqueurs(Set<Marqueur> marqueurs) {
        this.marqueurs = marqueurs;
    }

    @Override
    public boolean equals(Object other) {
        if (this.getId() == ((User) other).getId())
            return true;
        else
            return false;
    }

    @Override
    public int hashCode() {
        return id.hashCode();
    }
}

<hibernate-mapping>
   <class name="modele.User" table="user">
      <meta attribute="class-description">
         This class contains the user detail.
      </meta>
      <id name="id" type="java.lang.Integer" column="id">
         <generator class="native"/>
      </id>
      <property name="pseudo" column="pseudo" type="string"/>
      <property name="telephone" column="telephone" type="string" not-null="true" unique="true"/>
      <property name="email" column="email" type="string"/>

      <!--  Mapping Set<Demande> demandes -->
      <set name="demandes" lazy="false" inverse="true" cascade="all" >
         <key column="demandeur_id"/>       
         <one-to-many class="modele.Demande"/>
      </set>

      <!--  Mapping Set<Invitation> aInvite -->
      <set name="aInvite" lazy="false" inverse="true" cascade="all">
         <key column="inviteur_id"/>
         <one-to-many class="modele.Invitation"/>
      </set>

      <!--  Mapping Set<Notification> notifications -->
      <set name="notifications" lazy="false" inverse="true" cascade="all">
         <key column="user_id"/>
         <one-to-many class="modele.Notification"/>
      </set>

        <!--  Mapping Set<Group> groups -->
      <set name="groups"  table="participation" lazy="false">
         <key column="user_id"/>
         <many-to-many column="group_id" class="modele.Group"/>
      </set>

     <!--  Mapping Set<Group> proprietaire -->
      <set name="proprietaire" lazy="false" inverse="true" cascade="all">
         <key column="user_id"/>
         <one-to-many class="modele.Group"/>
      </set>     
      <!-- Mapping DernierePosition dernierePosition -->
      <one-to-one name="dernierePosition" class="modele.DernierePosition"
            cascade="all" lazy="false"></one-to-one>

      <!--  Mapping Set<Marqueur> marqueurs -->
      <set name="marqueurs" lazy="false" inverse="true" cascade="all">
         <key column="user_id"/>
         <one-to-many class="modele.Marqueur"/>
      </set>

   </class>
</hibernate-mapping>

public static User getUser(String telephone)
{
        Session session = sessionFactory.openSession();
        String query = "select u from User as u where u.telephone = :telephone";

        User user = (User) session.createQuery(query)
                .setString("telephone", telephone).uniqueResult();
        session.close();
        return user;
}

@Test
    public void getGroupsTest()
    {
        User user1 = new User("telU1","u1","mail");
        User prorio = new User("proprio","proprio","mail");
        UserDao.addUser(user1);
        UserDao.addUser(prorio);

        prorio =UserDao.getUser(prorio.getTelephone());
        user1 = UserDao.getUser(user1.getTelephone());

        Group g1 = new Group("description", "#h",prorio,"password");
        Group g2 = new Group("description", "#test",prorio,"password");
        Group g3 = new Group("description", "#test2",prorio,"password");
        Group g4 = new Group("description", "#test3",prorio,"password");

        g1.addParticipation(user1);
        g2.addParticipation(user1);
        g3.addParticipation(user1);
        g4.addParticipation(user1);

        GroupDao.addGroup(g1);
        GroupDao.addGroup(g2);
        GroupDao.addGroup(g3);
        GroupDao.addGroup(g4);

        User user2 = UserDao.getUser(user1.getTelephone());
        User pro = UserDao.getUser(prorio.getTelephone());
        Set<Group> groups =user2.getGroups();
        Set<Group> groups2 = pro.getProprietaire();

        System.out.println(user2.getPseudo());
        System.out.println(user2.getTelephone());
        System.out.println(pro.getPseudo());   
        System.out.println(pro.getTelephone());
        System.out.println(groups.size());
        System.out.println(groups2.size());
}

public static int addGroup(Group group) {
        int g = 0;
        Session session = sessionFactory.openSession();
        Transaction tx = null;

        try {
            tx = session.beginTransaction();
            g = (Integer) session.save(group);
            tx.commit();
        } catch (HibernateException e) {
            if (tx != null)
                tx.rollback();
            e.printStackTrace();
        } finally {
            session.close();
        }
        return g;
    }