Frankly speaking, I am running out ideas on how to get it work and I need your help please!!!!


is there a way to describe an association between any two tables where there are no foreign constraints at all in a hibernate mapping file.

Let me give you an example:

We have three tables: table1, table2, table3.
Table 1 and 2 have only a primary key column
Table3 has three columns: pk, relatedTableName, relatedObjPk

Table1 has following items:

PK
1
2

Table2 has following items:

PK
1
2
3

Table3 contains records from Table1 and Table2:

PK RelatedTableName RelatedObjID
1 Table1 1
2 Table1 2
3 Table2 1
3 Table2 2

We have three concrete classes Entity1, Entity2, and Entity3 for each of the Tables.

class Entity1
{
Long pk;

Collection<Entity3> entity3; // how to map this collection
}

class Entity2
{
Long pk;

Collection<Entity3> entity3; // how to map this collection
}

class Entity3
{
Long pk;
String relatedEntityName;
Long relatedEntityPk;

Object relatedObj; // this can be mapped using <any>
}

We want to know how to map the collections in Entity1 and 2 in hibernate mapping file so that we can use HQL to traverse the relationships.

Jianping

can't you use many-to-one tag and formula ?

<hibernate-mapping>
<class name="entity1" table="table1">
<id name="pk" />
<many-to-one
name="meInTab3"
property-ref="meInTab3">
<column name="pk"/>
<formula>'table1'</formula>
</many-to-one>
</class>
<class name="entity3" table="table3" >
<id name="pk" />
<properties name="meInTab3">
<property name="relatedObjPk" />
<property name="relatedTableName" />
</properties>
</class>
</hibernate-mapping>

I have read that it will produce sql like:

select t1.pk, t3.pk from table1 t1, tbale3 t3 where t3.relatedObjPk=t1.pk and p.relatedTableName='table1'

Well, I had a couple of mappings before, the problem is with the foreign keys. So the solution is not use hbm2ddl.auto at all to prevent hibernate from creating foreign keys like:

alter table table3 add constraint fk_t3_to_t2 foreign key (RelatedObjID) references table2(pk);

alter table table3 add constraint fk_t3_to_t1 foreign key (RelatedObjID) references table1(pk);

Mapping 1:

<class name="Entity1" table="table1">
<id name="pk" type="java.lang.Long" unsaved-value="null">
<column name="pk" sql-type="BIGINT"/>
<generator class="assigned">
</generator>
</id>
<set name="entities3"
lazy="false"
fetch="select"
inverse="true"
where="tablename = 'table1')">
<key>
<column name="relatedCol" sql-type="BIGINT"/>
</key>
<one-to-many class="Entity3"/>
</set>
</class>

Entity2 is very similar to Entity1.

Mapping 2:

Use collection loader. See an example from tests of hibernate download.