@Entity
@Table(name = T_PREFERENCES)
public class Preferences implements IPreferences {

    @Id
    @GeneratedValue
    @Column(name = I_PREFERENCES)
    private Long id;

    @ElementCollection
    @CollectionTable(name = J_PREFERENCES_DATA,
            joinColumns = {@JoinColumn(name = I_PREFERENCES, referencedColumnName = I_PREFERENCES)})
    @MapKeyColumn(name = M_PREFERENCES_DATA + "_KEY")
    private Map<String, String> data;

...



}