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Problems with composition and one-to-one

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refa

Post subject: Problems with composition and one-to-one

Posted: Tue Aug 23, 2005 9:39 am

Newbie

Joined: Mon Aug 15, 2005 8:03 am
Posts: 14
Location: Germany

Hi,

I've here a problem with one-to-one mapping.
I've tow classes Instrument and Option. The Relation between them is

Code:

  +------------+          +----------+
  | Instrument |          |  Option  |
  +------------+ 1   0..1 +----------+
  | id*        |<>--------| id*      |
  | ...        |          | inst_id  |
  +------------+          +----------+

Each classe has its own table defined as follows:

Code:

create table instrument (
   id int not null auto_increment primary key, 
   name varchar(30) not null
); 

create table option (
   id int not null auto_increment primary key,
   inst_id int not null,

   constraint instrument_option_fk_01 foreign key (inst_id) references instrument (id)
); 

The corresponig hbm file contains the definition of the classes and the one-to-one relation as follows:

Code:

<hibernate-mapping package="xxx" default-lazy="false">
   <class name="Instrument" table="instrument" lazy="false">
      <id name="id"
         column="id"
         type="int"
         unsaved-value="0"
      >
         <generator class="native"/>
      </id>
      <property
         name="Name"
         column="name"
         length="30"
         type="string"
         not-null="true"
       />
      
      <one-to-one
         name="option" 
         class="Option"
         fetch="join"
         lazy="false"
        /> 
   </class>

   <class name="Option" table="option" lazy="false">
      <id name="id" 
         column="id" 
         type="int" 
         unsaved-value="0"
      >
         <generator class="native"/>
      </id>
   </class>
</hibernate-mapping>

The call of my dao for loading all Instruments (my DAO is extending HibernateDaoSupport) is implemented as follows:

Code:

   public List<Instrument> getAll() {
      return getHibernateTemplate().loadAll(Instrument.class);
   }

In my data base I've three Instruments and two Options. The instrument with the id 1 is not referenced by any option. The instruments with id 2 and 3 are referenced by options with id 1 and 2.

After calling loadAll() I get all three Instruments but the option objects are not attached correctly. The first Instrument (with id 1) contains the first option and that with id 2 the another option. The third instrument doen't have any options.

It seems that the hibernate loads all instruments and all options and then starts to attach the options in the order of instruments. It doesn't take care of given inst_id.

What do I wrong.
I'm using hibernate 3.1 b2 with JDK 1.5. For tests I'm using MsSql 4.1

Thanks in advance,
Reza

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refa

Post subject:

Posted: Tue Aug 23, 2005 10:29 am

Newbie

Joined: Mon Aug 15, 2005 8:03 am
Posts: 14
Location: Germany

Hi,

I found it. The class Option needs an attribute instrument_id. That shoud be given in hbm for Instrument as property-ref.

The Problem I have now is, that in case of saving a new instrument, the corresponding Option has not been save automaticly.

Save just call:

Code:

getHibernateTemplate().saveOrUpdate(instrument);

.

How can I force hibernate to make a deep persistence?

Reza

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anar

Post subject:

Posted: Tue Aug 23, 2005 12:03 pm

Senior

Joined: Wed Jul 13, 2005 4:31 pm
Posts: 142
Location: Seattle, WA

add cascade attribute to the association...

Code:

   <one-to-one
         name="option"
         class="Option"
         fetch="join"
         lazy="false"
         cascade="all"
        />

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refa

Post subject:

Posted: Tue Aug 23, 2005 1:25 pm

Newbie

Joined: Mon Aug 15, 2005 8:03 am
Posts: 14
Location: Germany

hi anar,

anar wrote:

add cascade attribute to the association...

Code:

   <one-to-one
         name="option"
         class="Option"
         fetch="join"
         lazy="false"
         cascade="all"
        />

I did it and it works perfectly.

There is still a problem. By saving an Instrument hibernate tries to save also the associated Option.
I assumed that hibernate firstly stores instrument and then sets the filed inst_id of the option to the generated id of the instrument and then stores the option.
hibernate stores the instrument but doesn't set the filed inst_id of the option and the storing fails with following message:

Code:

WARN JDBCExceptionReporter:71 - SQL Error: 1216, SQLState: 23000
ERROR JDBCExceptionReporter:72 - Cannot add or update a child row: a foreign key constraint fails

The hbn part is:

Code:

      <one-to-one
         name="option" 
         class="Option"
         fetch="join"
         lazy="false"
         property-ref="instrumentId"
         cascade="all"
      /> 

and Option is defined as follows:
   <class name="Option" table="option" lazy="false">
      <id name="id" 
         column="id" 
         type="int" 
         unsaved-value="0"
      >
         <generator class="native"/>
      </id>
      <property
         name="instrumentId"
         column="instrument_id"
         type="int"
       />
   </class>

How can I say hibernet to set the field inst_id to the value of instrument.id before saving option.

As workaround I remove the condition of foreign key for option and allow the inst_id to be null. It works now correctly, the inst_id of the Option won't be set!!!

Any idea?

Regards,
Reza

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anar

Post subject:

Posted: Tue Aug 23, 2005 1:54 pm

Senior

Joined: Wed Jul 13, 2005 4:31 pm
Posts: 142
Location: Seattle, WA

I think you need to set constrained for the mapping

Try

<one-to-one
name="option"
class="Option"
fetch="join"
lazy="false"
property-ref="instrumentId"
cascade="all"
constrained="false"
/>

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