<joined-subclass name="Customer" extends="security.domain.User" table="CUSTOMER"
       abstract="false">
       <key column="CUSTOMER_ID"/>
       <!-- some stuff afteward -->
</joined subclass>

<joined-subclass name="Agency" extends="security.domain.User" table="AGENCY"
       abstract="false">
       <key column="AGENCY_ID"/>
       <!-- some stuff afteward -->
</joined subclass>

<hibernate-mapping package="security.domain">
  <class name="User" table="CS_USER">
      <id name="id" column="CS_USER_ID" access="field">
          <generator class="sequence">
            <param name="sequence">USER_ID_SEQ</param>
          </generator>
       </id>
      <!-- some stuff afteward -->
  </class>
</hibernate-mapping>

userService.getUserById(1)

/* load security.domain.User */ select
user0_.CS_USER_ID as CS1_44_0_,
        user0_.USER_NAME as USER2_44_0_,
        user0_.USER_EMAIL as USER3_44_0_,
        user0_.PASSPHRASE as PASSPHRASE44_0_,
        user0_.USER_STATUS_ID as USER5_44_0_,
        user0_.FIRST_NAME as FIRST6_44_0_,
        user0_.LAST_NAME as LAST7_44_0_,
        user0_.CREATE_USER_ID as CREATE8_44_0_,
        user0_.CREATE_TIME as CREATE9_44_0_,
        user0_.MODIFY_USER_ID as MODIFY10_44_0_,
        user0_.MODIFY_TIME as MODIFY11_44_0_,
        user0_1_.AGENCY_NAME as AGENCY2_55_0_,
        user0_1_.AGENCY_TYPE_ID as AGENCY3_55_0_,
        user0_1_.AGENCY_STATUS_ID as AGENCY4_55_0_,
        user0_1_.CREATE_USER_ID as CREATE5_55_0_,
        user0_1_.CREATE_TIME as CREATE6_55_0_,
        user0_1_.MODIFY_USER_ID as MODIFY7_55_0_,
        user0_1_.MODIFY_TIME as MODIFY8_55_0_,
        user0_1_.DISCOUNT_ID as DISCOUNT9_55_0_,
        user0_2_.BUSINESS_NAME as BUSINESS2_56_0_,
        user0_2_.AFFILIATE_ID as AFFILIATE3_56_0_,
        user0_2_.COMPANY_ID as COMPANY4_56_0_,
        user0_2_.AGENCY_ID as AGENCY5_56_0_,
        user0_2_.CUSTOMER_STATUS_ID as CUSTOMER6_56_0_,
        user0_2_.CREATE_USER_ID as CREATE7_56_0_,
        user0_2_.CUSTOMER_TYPE_ID as CUSTOMER8_56_0_,
        user0_2_.CREATE_TIME as CREATE9_56_0_,
        user0_2_.MODIFY_USER_ID as MODIFY10_56_0_,
        user0_2_.MODIFY_TIME as MODIFY11_56_0_,
        case
            when user0_1_.AGENCY_ID is not null then 1
            when user0_2_.CUSTOMER_ID is not null then 2
            when user0_.CS_USER_ID is not null then 0
        end as clazz_0_
    from
        CS_USER user0_
    left outer join
        AGENCY user0_1_
            on user0_.CS_USER_ID=user0_1_.AGENCY_ID
    left outer join
        CUSTOMER user0_2_
            on user0_.CS_USER_ID=user0_2_.CUSTOMER_ID
    where
        user0_.CS_USER_ID=?