java - Hibernate: foreign key partially used as primary key -

i have been working hours trying solve problem, seems quite simple database point of view hard figure out hibernate.

i have got 2 tables: vehiclecategory, , vehicle.

a vehicle has 1 vehiclecategory, vehicule references vehiculecategory using foreign key.

vehiclecategory:

• string attr1
• string attr2
• integer attr3
• string attr4
• primary key (attr1, attr2, attr3, attr4)

vehicle

• string name
• string attr1
• string attr2
• integer attr3
• string attr4
• foreign key (attr1, attr2, attr3, attr4) references vehiclecategory
• primary key (name, attr1, attr2, attr3)

here point: do not want use attr4 primary key, want use other foreign attributes in primary key.

this mapping did:

<class name="vehicle" table="vehicle">     <composite-id>         <key-property name="name" column="name"/>         <key-many-to-one name="vehiclecategory" class="vehiclecategory">             <column name="attr1" not-null="true" />             <column name="attr2" not-null="true" />             <column name="attr3" not-null="true" />         </key-many-to-one>      </composite-id>      <many-to-one name="vehiclecategory" class="vehiclecategory" fetch="select" insert="false" update="false" >         <column name="attr1" not-null="true" />         <column name="attr2" not-null="true" />         <column name="attr3" not-null="true" />         <column name="attr4" not-null="true" />     </many-to-one> </class> 

i following exception:

 foreign key (fk_s94md9vv63hrpwhyaw4rfxec5:vehicle [attr1,attr2,attr3])) must have same number of columns referenced primary key (vehicle_category [attr4,attr1,attr2,attr3]) 

i understand exception means. not see why because, point of view, did reference 4-columns primary key in foreign key, , used 3 in vehicule primary key.

i using hibernate 4.3.6

thank !