@Entity
@Table(name = "user")
public class User {

   @OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
   @MapKeyColumn(name = "AppId", insertable = false, updatable = false)
   @MapKeyEnumerated(EnumType.STRING)
   private Map<ApplicationsEnum, AbstractAccount>   accounts;

}

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "accounts")
public abstract class Account {

    @EmbeddedId
    private AccountID id;

    @ManyToOne
    @MapsId("id")
    @JoinColumn(name = "UserId", referencedColumnName = "Id")
    private Utilisateur user;
}

@Embeddable
public class AccountID implements Serializable {

    @Column(name = "UserId")
    private Long id;

    @Column(name = "AppId")
    @Enumerated(EnumType.STRING)
    private ApplicationsEnum AppId;
}

"select distinct user
 from User user
 left join fetch user.accounts accounts on (TYPE(accounts) = AccountA or TYPE(accounts) = AccountB)"