SOLVED: A foreign key constraint fails

klogger · **Joined:** Thu Mar 27, 2008 8:49 am **Posts:** 27

I have looked all over for the answer to this and haven't been successful but I am sure the solution is simple!

I have two tables

Table Tracker

Code:

CREATE  TABLE IF NOT EXISTS `Tracker` (
  `tracker_id` INT NOT NULL AUTO_INCREMENT ,
  `configuration_id` INT ,
  PRIMARY KEY (`tracker_id`) ,
  INDEX `fk_Tracker_configuration_id` (`configuration_id` ASC) ,
  CONSTRAINT `fk_Tracker_configuration_id`
    FOREIGN KEY (`configuration_id` )
    REFERENCES `TrackerConfiguration` (`configuration_id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

Table TrackerConfiguration

Code:

CREATE  TABLE IF NOT EXISTS `TrackerConfiguration` (
  `configuration_id` INT NOT NULL AUTO_INCREMENT ,
  PRIMARY KEY (`configuration_id`) )

These are the auto-generated by hibernate-tool:

Code:

<class name="uk.co.prodia.prosoc.domainmodel.Tracker" table="Tracker" catalog="habittracker">
        <id name="trackerId" type="java.lang.Integer">
            <column name="tracker_id" />
            <generator class="identity" />
        </id>
        <many-to-one name="TrackerConfiguration" class="uk.co.prodia.prosoc.domainmodel.TrackerConfiguration" fetch="select">
            <column name="configuration_id" not-null="true" />
        </many-to-one>
    </class>

Code:

    <class name="uk.co.prodia.prosoc.domainmodel.TrackerConfiguration" table="TrackerConfiguration" catalog="habittracker">
        <id name="configurationId" type="java.lang.Integer">
            <column name="configuration_id" />
            <generator class="identity" />
        </id>
        <set name="Trackers" inverse="true" lazy="true" table="Tracker" fetch="select">
            <key>
                <column name="configuration_id" not-null="true" />
            </key>
            <one-to-many class="uk.co.prodia.prosoc.domainmodel.Tracker" />
        </set>
    </class>

I load both sides of the relentionship so that:

Code:

tracker.setTrackerConfiguration(trackerConfiguration);
trackerConfiguration.setTrackers(hashSetOfTrackers);

save(tracker)

I can only get this to work if I:

First extract the TrackerConfiguration from the Tracker;
call save(trackerConfiguration);
call save(tracker).

Without first saving the child, I can't save the parent as the child's ID is null. Any ideas please?

Froestel · **Posted:** Thu Jan 07, 2010 7:09 pm

Hi klogger,

klogger wrote:

Code:

    <class name="uk.co.prodia.prosoc.domainmodel.TrackerConfiguration" table="TrackerConfiguration" catalog="habittracker">
        <id name="configurationId" type="java.lang.Integer">
            <column name="configuration_id" />
            <generator class="identity" />
        </id>
        <set name="Trackers" inverse="true" lazy="true" table="Tracker" fetch="select">
            <key>
                <column name="configuration_id" not-null="true" />
            </key>
            <one-to-many class="uk.co.prodia.prosoc.domainmodel.Tracker" />
        </set>
    </class>

Have you tried to set the cascade attribute in the set element of the mapping. You might want to check out Transitive Persistence in the Hibernate Docs.

CU
Froestel

klogger · **Joined:** Thu Mar 27, 2008 8:49 am **Posts:** 27

Thanks for taking the time to reply Froestel.

I did try to set cascade to 'all' as well as 'save-update' and 'persist' on both sides of the relentionship but it didn't help. I think you have pointed me in the right direction though. The Transitive persistence does sound like it is causing the issue here, I am just a little unsure why setting the cascade option didn't work.

klogger · **Joined:** Thu Mar 27, 2008 8:49 am **Posts:** 27

OK, you were right. I had gotten the parent/child relentionship the wrong way round. It is my TrackerConfiguration that is the parent so I needed to call:

Code:

save(trackerConfiguration);

where I was calling:

Code:

save(tracker);

and that saves the Tracker child. I also needed the cascade="persist,merge,save-update" that you mentioned.

Many thanks for your help.