Problems with one-to-many inverse relationship and subclass

justinwalsh · **Joined:** Wed Feb 15, 2012 11:38 am **Posts:** 9

Hi,

Hibernate 3.5.4-Final, but same problem manifests with 3.6.10.Final

I have run into a problem with an inverse one-to-many bi-directional relationship which references a subclass from a parent (abstract) class. The following simplification demonstrates my problem:

I have the following inheritance hierarchy:

Code:

                     AbstractContainer
                       /           \
                 Container         Item                                              

An AbstractContainer (i.e. an Item or a Container) contains a collection of Items (not illustrated). This collection is mapped with inverse=true and is bi-directional.

I have mapped these classes as follows:
Hibernate mappings

Code:

<hibernate-mapping>

  <class abstract="true" name="test.hibernate.subclassjoinedtoparent.AbstractContainer" table="TBL_ABSTRACT_CONTAINER"
    discriminator-value="ABSTRACT_CONTAINER">

    <id name="id" column="ID" unsaved-value="null">
      <generator class="native" />
    </id>

    <discriminator column="ACTUAL_TYPE" type="string" />

    <list name="items" cascade="all" inverse="false">
      <key column="CONTAINER_ID" />
      <list-index column="INDEX" />
      <one-to-many class="test.hibernate.subclassjoinedtoparent.Item" />
    </list>

    <!-- Container subclass -->
    <subclass name="test.hibernate.subclassjoinedtoparent.Container" discriminator-value="CONTAINER" />

    <!-- Item subclass -->
    <subclass name="test.hibernate.subclassjoinedtoparent.Item" discriminator-value="ITEM">

      <join table="TBL_ITEM">
        <key column="ID" />

        <many-to-one name="container" column="CONTAINER_ID" class="test.hibernate.subclassjoinedtoparent.AbstractContainer"
          not-null="true" foreign-key="FK_CONTAINERID" />
          
      </join>

    </subclass>

  </class>

</hibernate-mapping>

Using this mapping, I have a very simple test case which creates a Container and adds an item in one transaction:

Source code

Code:

SessionFactory sessionFactory = 
            new Configuration().configure("hibernate-subclassjoinedtoparent.cfg.xml").buildSessionFactory();

        AbstractContainer container;
        Item item;
        
        Session session = sessionFactory.openSession();
        try {

            session.beginTransaction();
            container = new Container();
            
            item = new Item();
            container.addItem(item);

            session.save(container);
            session.flush();
            
            System.out.println("TX #1: Saved container with id: " + container.getId());
            System.out.println("TX #1: Container has " + container.getItems().size() + " items.");
            
            session.getTransaction().commit();
        }
        finally {
            session.close();
        }

Then, in a second transaction (session) immediately after the first code (same test method) I look up the container and get the size of the items:

Code:

        session = sessionFactory.openSession();
        try {

            session.beginTransaction();
            
            AbstractContainer savedContainer = (AbstractContainer)session.get(AbstractContainer.class, container.getId());
            System.out.println("TX #2: Found the container with id: " + savedContainer.getId());
            
            System.out.println("TX #2: Container has " + savedContainer.getItems().size() + " items.");
            session.getTransaction().commit();
        }
        finally {
            session.close();
        }

The output is as follows:

Code:

TX #1: Saved container with id: 1
TX #1: Container has 1 items.
Hibernate: select abstractco0_.ID as ID0_0_, abstractco0_1_.CONTAINER_ID as CONTAINER2_1_0_, abstractco0_.ACTUAL_TYPE as ACTUAL2_0_0_ from TBL_ABSTRACT_CONTAINER abstractco0_ left outer join TBL_ITEM abstractco0_1_ on abstractco0_.ID=abstractco0_1_.ID where abstractco0_.ID=?
TX #2: Found the container with id: 1
Hibernate: select items0_.CONTAINER_ID as CONTAINER3_0_1_, items0_.ID as ID1_, items0_.INDEX as INDEX1_, items0_.ID as ID0_0_, items0_1_.CONTAINER_ID as CONTAINER2_1_0_ from TBL_ABSTRACT_CONTAINER items0_ inner join TBL_ITEM items0_1_ on items0_.ID=items0_1_.ID where items0_.CONTAINER_ID=?
TX #2: Container has 0 items.

A couple of things that I have noticed
1) The effect of inverse=true
Note the last line:
TX #2: Container has 0 items.

If I turn the relationship to inverse="false", I get:
TX #2: Container has 1 items.

2) The DDL (on postgres):
Notice the container_id column in the TBL_ABSTRACT_CONTAINER table. Interestingly, it appears never to be populated.

Code:

Table "public.tbl_abstract_container"
    Column    |          Type          | Modifiers 
--------------+------------------------+-----------
 id           | bigint                 | not null
 actual_type  | character varying(255) | not null
 container_id | bigint                 | 
 index        | integer                | 
Indexes:
    "tbl_abstract_container_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "fkc86866c569382e12" FOREIGN KEY (container_id) REFERENCES tbl_abstract_container(id)

      Table "public.tbl_item"
    Column    |  Type  | Modifiers 
--------------+--------+-----------
 id           | bigint | not null
 container_id | bigint | not null
Indexes:
    "tbl_item_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "fk404b7b1461f77f4" FOREIGN KEY (id) REFERENCES tbl_abstract_container(id)
    "fk_containerid" FOREIGN KEY (container_id) REFERENCES tbl_abstract_container(id)

3. The insert statement:
Notice that the insert of the CONTAINER_ID happens in the TBL_ITEM table only

Code:

Hibernate: insert into TBL_ABSTRACT_CONTAINER (ACTUAL_TYPE, ID) values ('CONTAINER', ?)
Hibernate: insert into TBL_ABSTRACT_CONTAINER (ACTUAL_TYPE, ID) values ('ITEM', ?)
Hibernate: insert into TBL_ITEM (CONTAINER_ID, ID) values (?, ?)

4. The query used to select the items.

Notice that the query is selecting on the foreign key in the TBL_ABSTRACT_CONTAINER table - which is the column that is NOT populated during the insert

Code:

select ... 
from TBL_ABSTRACT_CONTAINER items0_ 
inner join TBL_ITEM items0_1_ on items0_.ID=items0_1_.ID 
where items0_.CONTAINER_ID=?

Any ideas would be much appreciated

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

According Hibernate documentation, when using bidirectional relation you always must set both sides of the relation.

Code:

container.addItem(item);

I is not enough, correct is:

Code:

container.addItem(item);
item.container=container;

justinwalsh · **Joined:** Wed Feb 15, 2012 11:38 am **Posts:** 9

Yes - I am updating both sides of the relationship in the Container.addItem(Item) method:

Code:

    public void addItem(Item toAdd) {
        toAdd.setContainer(this);
        getItems().add(toAdd);
    }

I'm happy to supply anyone with a simple maven project which illustrates the problem -just send an email to yojustinwalsh a-t gmail d-o-t com

Here is the source code for the java classes involved:
AbstractContainer.java

Code:

package test.hibernate.subclassjoinedtoparent;

import java.util.ArrayList;
import java.util.List;

public abstract class AbstractContainer {
    
    private Long id;
    private List<Item> items = new ArrayList<Item>();
    
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    
    public List<Item> getItems() {
        return items;
    }
    public void setItems(List<Item> items) {
        this.items = items;
    }
    public void addItem(Item toAdd) {
        toAdd.setContainer(this);
        getItems().add(toAdd);
    }

}

Container.java

Code:

package test.hibernate.subclassjoinedtoparent;

public class Container extends AbstractContainer {
}

Item.java

Code:

package test.hibernate.subclassjoinedtoparent;

public class Item extends AbstractContainer {
    
    private AbstractContainer container;
    
    public AbstractContainer getContainer() {
        return container;
    }
    public void setContainer(AbstractContainer container) {
        this.container = container;
    }
}

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

Hi justinwalsh,

in your application-code you forgot to persist the child item,
since you are not using regarding cascade option, you must persist each new entity object manually.

Quote:

session.beginTransaction();
container = new Container();

item = new Item();

session.save(item); // or session.persist(item); this instruction is necessary here as you are not using Cascade options
container.addItem(item);

session.save(container);
session.flush();

I rebuilded your example with annotations (I'm not familiar with hibernate mapping files) and after this change it worked as excpected

justinwalsh · **Joined:** Wed Feb 15, 2012 11:38 am **Posts:** 9

Hi pb00067

Quote:

since you are not using regarding cascade option, you must persist each new entity object manually.

My hibernate configuration is explicitly cascading all operations of the list collection in the AbstractContainer class to the Item objects:

Code:

    <list name="items" cascade="all" inverse="true">
      <key column="CONTAINER_ID" />
      <list-index column="INDEX" />
      <one-to-many class="test.hibernate.subclassjoinedtoparent.Item" />
    </list>

I tried to put the code that you suggested in, but then I get the following error:

Code:

20 Feb 2012 12:28:47 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: ERROR: null value in column "container_id" violates not-null constraint
org.hibernate.exception.ConstraintViolationException: ERROR: null value in column "container_id" violates not-null constraint
        at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:128)
        at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)

I've uploaded the sample application to dropbox: http://dl.dropbox.com/u/40954387/subcla ... parent.zip
Just extract the archive, create a database named TEST with a username and password of username/password (or change the settings in the file hibernate-subclassjoinedtoparent.cfg.xml) and then run:
mvn clean install

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

Quote:

My hibernate configuration is explicitly cascading all operations

Oh you are right, sorry I missed to see that.

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

Hi justinwalsh,

from the book "Java Persistence with Hiberante" chapter Unidirectional and bidirectional lists:

Quote:

If you map a bidirectional ano-to-many entity association with an indexed collection, you have to switch the inverse sides.
You can't make an indexed collection inverse="true"

xiaotuanzi · **Joined:** Tue Feb 21, 2012 12:57 am **Posts:** 5

I can't know these.

strjames · **Joined:** Fri Feb 17, 2012 8:20 am **Posts:** 18

Seems you are looking for this....

Hibernate One To Many Bidirectional Mapping Example

Or see one to many related, those are good i guess, good luck.

justinwalsh · **Joined:** Wed Feb 15, 2012 11:38 am **Posts:** 9

Thanks strjames, but this is a problem involving a subclass. Its not as trivial as the example that you posted. Download the example from the drop box address mentioned above and run it on your machine.

pb00067: I replaced the indexed collection with a set, updating the hibernate mappings and the AbstractContainer class.

The set is mapped as follows:

Code:

    <set name="items" cascade="all" inverse="true">
      <key column="CONTAINER_ID" />
      <one-to-many class="test.hibernate.subclassjoinedtoparent.Item" />
    </set>

The AbstractContainer class is as follows:

Code:

public abstract class AbstractContainer {
    
    private Long id;
    private Set<Item> items = new HashSet<Item>();
    
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    
    public Set<Item> getItems() {
        return items;
    }
    public void setItems(Set<Item> items) {
        this.items = items;
    }
    public void addItem(Item toAdd) {
        toAdd.setContainer(this);
        getItems().add(toAdd);
    }
}

The output is the same:

Code:

INFO: schema export complete
Hibernate: select nextval ('hibernate_sequence')
Hibernate: select nextval ('hibernate_sequence')
Hibernate: insert into TBL_ABSTRACT_CONTAINER (ACTUAL_TYPE, ID) values ('CONTAINER', ?)
Hibernate: insert into TBL_ABSTRACT_CONTAINER (ACTUAL_TYPE, ID) values ('ITEM', ?)
Hibernate: insert into TBL_ITEM (CONTAINER_ID, ID) values (?, ?)
TX #1: Saved container with id: 1
TX #1: Container has 1 items.
Hibernate: select abstractco0_.ID as ID0_0_, abstractco0_1_.CONTAINER_ID as CONTAINER2_1_0_, abstractco0_.ACTUAL_TYPE as ACTUAL2_0_0_ from TBL_ABSTRACT_CONTAINER abstractco0_ left outer join TBL_ITEM abstractco0_1_ on abstractco0_.ID=abstractco0_1_.ID where abstractco0_.ID=?
TX #2: Found the container with id: 1
Hibernate: select items0_.CONTAINER_ID as CONTAINER3_0_1_, items0_.ID as ID1_, items0_.ID as ID0_0_, items0_1_.CONTAINER_ID as CONTAINER2_1_0_ from TBL_ABSTRACT_CONTAINER items0_ inner join TBL_ITEM items0_1_ on items0_.ID=items0_1_.ID where items0_.CONTAINER_ID=?
TX #2: Container has 0 items.

Notice that the insert is done into the TBL_ITEM table:

Code:

Hibernate: insert into TBL_ITEM (CONTAINER_ID, ID) values (?, ?)

But the query is run against the TBL_ABSTRACT_CONTAINER table:

Code:

Hibernate: select items0_.CONTAINER_ID as CONTAINER3_0_1_, items0_.ID as ID1_, items0_.ID as ID0_0_, items0_1_.CONTAINER_ID as CONTAINER2_1_0_ from TBL_ABSTRACT_CONTAINER items0_ inner join TBL_ITEM items0_1_ on items0_.ID=items0_1_.ID where items0_.CONTAINER_ID=?

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

Hi justinwalsh,

when you choose for inverse="true" then you don't need a join-table anymore,
therefore I think you must also remove the join table specification

Code:

<join table="TBL_ITEM"> ...

and rebuild the database schema from scratch.

justinwalsh · **Joined:** Wed Feb 15, 2012 11:38 am **Posts:** 9

Hi pb00067

The join table configuration has nothing to do with the bi-directional association that I am mapping - its got to do with the way in which I've mapped the subclass (using the table per subclass with discriminator approach).

Remember - this is a simplified example of a complex problem that I am having in a an environment. In 'real life' the Item subclass has a number of other properties and associations that are mapped in this subclass specification. So I can't simply remove the subclass or the way in which I've mapped it.

So to summarise the problem - if I have a subclass (with a discriminator), and a bi-directional association from this subclass to a parent of the subclass (with the many side in the subclass) - then hibernate fails to correctly return the values of the collection.

Here's a link to an eclipse maven project demonstrating the issue with a bi-directional set. Simply unzip the project, change your database settings in hibernate-subclassjoinedtoparent.cfg.xml and:
mvn test

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

Quote:

The join table configuration has nothing to do with the bi-directional association that I am mapping

you are right.
Sorry I'm not familiar with Table per subclass strategy
I use exclusively Table per class hierarchy and Table per concrete class strategies in my projects so far, so I fear that I cannot help you.
All I can see is that your example produces a very strange query when tries to load the collection of items of container nr 1,
so I think its a Hibernate bug:

Quote:

p6spy - 1329904559742|0|0|statement

select
items0_.CONTAINER_ID as CONTAINER3_0_1_,
items0_.ID as ID1_,
items0_.ID as ID0_0_,
items0_1_.CONTAINER_ID as CONTAINER2_1_0_
from
TBL_ABSTRACT_CONTAINER items0_
inner join
TBL_ITEM items0_1_
on items0_.ID=items0_1_.ID
where
items0_.CONTAINER_ID=1
TX #2: Container has 0 items.

justinwalsh · **Joined:** Wed Feb 15, 2012 11:38 am **Posts:** 9

Thanks pb00067 for your time.

Before I log this a hibernate bug, does anyone else have any insight into this problem?

pb00067 · **Joined:** Tue Jun 16, 2009 3:36 am **Posts:** 990

Hi justinwalsh,

when using Table per subclass with discriminator,
Hibernate in my opinion get confused if the collection is between classes of the same hierarchy.
Look here how hibernate created the schema (HSQLDB isntead of Postgres):

Quote:

create table TBL_ABSTRACT_CONTAINER (
ID bigint generated by default as identity (start with 1),
ACTUAL_TYPE varchar(255) not null,
CONTAINER_ID bigint, // <- why Hibernate puts this column here ?!, this column should be exclusively be mapped on table TBL_ITEM
primary key (ID))

Finally the query is also constructed wrong in my opinion:

Quote:

select
items0_.CONTAINER_ID as CONTAINER3_0_1_,
items0_.ID as ID1_,
items0_.ID as ID0_0_,
items0_1_.CONTAINER_ID as CONTAINER2_2_0_
from
TBL_ABSTRACT_CONTAINER items0_
inner join
TBL_ITEM items0_1_
on items0_.ID=items0_1_.ID
where
items0_.CONTAINER_ID=1 // wrong, right would be: where items0_1_.CONTAINER_ID=1

I was able to made the example run correctly when renouncing to discriminators,
I used following mapping:

Code:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

  <class abstract="true" name="test.hibernate.subclassjoinedtoparent.AbstractContainer" table="TBL_ABSTRACT_CONTAINER">

    <id name="id" column="ID" unsaved-value="null">
      <generator class="native" />
    </id>

    <set name="items" cascade="all" inverse="true">
      <key column="CONTAINER_ID" />
      <one-to-many class="test.hibernate.subclassjoinedtoparent.Item" />
    </set>

    <!-- Container subclass -->
    <joined-subclass name="test.hibernate.subclassjoinedtoparent.Container" table="TBL_CONTAINER">
       <key column="ID" />
    </joined-subclass>
    

    <!-- Item subclass -->
    <joined-subclass name="test.hibernate.subclassjoinedtoparent.Item" table="TBL_ITEM">
        <key column="ID" />
        <many-to-one name="container" column="CONTAINER_ID" class="test.hibernate.subclassjoinedtoparent.AbstractContainer"
          not-null="true" foreign-key="FK_CONTAINERID" />
    </joined-subclass>

  </class>

</hibernate-mapping>

Here the Output:

Quote:

1329917021887|0|0|statement||create table TBL_ABSTRACT_CONTAINER (ID bigint generated by default as identity (start with 1), primary key (ID))
1329917021888|1|0|statement||create table TBL_CONTAINER (ID bigint not null, primary key (ID))
1329917021888|0|0|statement||create table TBL_ITEM (ID bigint not null, CONTAINER_ID bigint not null, primary key (ID))
1329917021888|0|0|statement||alter table TBL_CONTAINER add constraint FKA78A2D0049A676EA foreign key (ID) references TBL_ABSTRACT_CONTAINER
1329917021888|0|0|statement||alter table TBL_ITEM add constraint FK404B7B1449A676EA foreign key (ID) references TBL_ABSTRACT_CONTAINER
1329917021889|1|0|statement||alter table TBL_ITEM add constraint FK_CONTAINERID foreign key (CONTAINER_ID) references TBL_ABSTRACT_CONTAINER
1329917021928|1|0|statement|insert into TBL_ABSTRACT_CONTAINER (ID) values (null)|insert into TBL_ABSTRACT_CONTAINER (ID) values (null)
1329917021930|2|0|statement|call identity()|call identity()
1329917021936|0|0|statement|insert into TBL_CONTAINER (ID) values (?)|insert into TBL_CONTAINER (ID) values (1)
1329917021940|0|0|statement|insert into TBL_ABSTRACT_CONTAINER (ID) values (null)|insert into TBL_ABSTRACT_CONTAINER (ID) values (null)
1329917021940|0|0|statement|call identity()|call identity()
1329917021941|0|0|statement|insert into TBL_ITEM (CONTAINER_ID, ID) values (?, ?)|insert into TBL_ITEM (CONTAINER_ID, ID) values (1, 2)
TX #1: Saved container with id: 1
TX #1: Container has 1 items.
1329917021946|0|0|commit||
1329917021953|3|0|statement|select abstractco0_.ID as ID0_0_, abstractco0_2_.CONTAINER_ID as CONTAINER2_2_0_, case when abstractco0_1_.ID is not null then 1 when abstractco0_2_.ID is not null then 2 when abstractco0_.ID is not null then 0 end as clazz_0_ from TBL_ABSTRACT_CONTAINER abstractco0_ left outer join TBL_CONTAINER abstractco0_1_ on abstractco0_.ID=abstractco0_1_.ID left outer join TBL_ITEM abstractco0_2_ on abstractco0_.ID=abstractco0_2_.ID where abstractco0_.ID=?|select abstractco0_.ID as ID0_0_, abstractco0_2_.CONTAINER_ID as CONTAINER2_2_0_, case when abstractco0_1_.ID is not null then 1 when abstractco0_2_.ID is not null then 2 when abstractco0_.ID is not null then 0 end as clazz_0_ from TBL_ABSTRACT_CONTAINER abstractco0_ left outer join TBL_CONTAINER abstractco0_1_ on abstractco0_.ID=abstractco0_1_.ID left outer join TBL_ITEM abstractco0_2_ on abstractco0_.ID=abstractco0_2_.ID where abstractco0_.ID=1
1329917021955|-1||resultset|select abstractco0_.ID as ID0_0_, abstractco0_2_.CONTAINER_ID as CONTAINER2_2_0_, case when abstractco0_1_.ID is not null then 1 when abstractco0_2_.ID is not null then 2 when abstractco0_.ID is not null then 0 end as clazz_0_ from TBL_ABSTRACT_CONTAINER abstractco0_ left outer join TBL_CONTAINER abstractco0_1_ on abstractco0_.ID=abstractco0_1_.ID left outer join TBL_ITEM abstractco0_2_ on abstractco0_.ID=abstractco0_2_.ID where abstractco0_.ID=1|clazz_0_ = 1
TX #2: Found the container with id: 1
1329917021959|0|0|statement|select items0_.CONTAINER_ID as CONTAINER2_0_1_, items0_.ID as ID1_, items0_.ID as ID0_0_, items0_.CONTAINER_ID as CONTAINER2_2_0_ from TBL_ITEM items0_ inner join TBL_ABSTRACT_CONTAINER items0_1_ on items0_.ID=items0_1_.ID where items0_.CONTAINER_ID=?|select items0_.CONTAINER_ID as CONTAINER2_0_1_, items0_.ID as ID1_, items0_.ID as ID0_0_, items0_.CONTAINER_ID as CONTAINER2_2_0_ from TBL_ITEM items0_ inner join TBL_ABSTRACT_CONTAINER items0_1_ on items0_.ID=items0_1_.ID where items0_.CONTAINER_ID=1
1329917021960|-1||resultset|select items0_.CONTAINER_ID as CONTAINER2_0_1_, items0_.ID as ID1_, items0_.ID as ID0_0_, items0_.CONTAINER_ID as CONTAINER2_2_0_ from TBL_ITEM items0_ inner join TBL_ABSTRACT_CONTAINER items0_1_ on items0_.ID=items0_1_.ID where items0_.CONTAINER_ID=1|CONTAINER2_0_1_ = 1, CONTAINER2_2_0_ = 1, ID0_0_ = 2, ID1_ = 2
TX #2: Container has 1 items.
1329917021963|0|0|commit||