many-to-one association problem

suomi99 · **Joined:** Mon Aug 09, 2010 3:39 pm **Posts:** 7

I have a class StaffSchedule which has mant to one relationship with another class Staff. See below:

Code:

<class name="StaffSchedule" table="TC_StaffSchedule">
.......      
      <many-to-one name="staffId" column="staffId" 
      class="test.Staff" not-null="true"/>
........
/class>

The class Staff has a PK called id. In my code I am trying to find all the schedules for a given staffId. See below:

Code:

List<StaffSchedule> staffScheduleList = session.createCriteria(StaffSchedule.class)
                     .add(Restrictions.eq("staffId", staffId)).list();

This is throwing an exception:

Code:

Caused by: org.hibernate.PropertyAccessException: IllegalArgumentException occurred calling getter of test.Staff.id
Caused by: java.lang.IllegalArgumentException: object is not an instance of declaring class

However if I change my many to one association as follows I get a different error.

Code:

<many-to-one name="staffId" column="staffId" 
      class="test.Staff" property-ref="id" not-null="true"/>

The default value of property-ref should be the PK of the Staff (id), so the property-ref should NOT have made any difference, but see below:

Code:

Service method 'public abstract java.util.List test.StaffSchedulerService.getAllSchedules(long)' threw an unexpected exception: java.lang.NullPointerException
....
Caused by: java.lang.NullPointerException
   at org.hibernate.tuple.entity.AbstractEntityTuplizer.getPropertyValue(AbstractEntityTuplizer.java:524)
   at org.hibernate.persister.entity.AbstractEntityPersister.getPropertyValue(AbstractEntityPersister.java:3844)
   at org.hibernate.type.EntityType.getIdentifier(EntityType.java:456)
   at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:141)
...

I am confused! I am using Java 1.6 with Hibernate 3.5.3.
Any pointers?

shynate26 · **Posted:** Tue Aug 10, 2010 3:33 am

Hi Saoumi99,

You can also use HQL query.

Code:

List staffScheduleList  = session.createQuery("Example"."from StaffSchedule ss where ss.staffId.identifier=:staffIdentifier").setLong("staffIdentifier",value).list();

Try this and let me know.

nordborg · **Posted:** Tue Aug 10, 2010 4:40 am

There is probably something wrong with your entity classes. Check that your StaffSchedule.getStaffId() really returns a Staff object.

suomi99 · **Joined:** Mon Aug 09, 2010 3:39 pm **Posts:** 7

Thanks for your response shynate26. The query works when I use HQL, though I cannot see any difference in the SQL that Hibernate generates in both cases, see below.

SQL generated by query using Criteria:

Code:

List<StaffSchedule> staffScheduleList = session.createQuery(
            "from StaffSchedule ss where ss.staffId=:staffIdentifier").setLong("staffIdentifier",staffId).list();
select
        staffsched0_.id as id6_,
        staffsched0_.staffId as staffId6_,
        staffsched0_.startDate as startDate6_,
        staffsched0_.endDate as endDate6_
    from
        TC_StaffSchedule staffsched0_ 
    where
        staffsched0_.staffId=?

And SQL generated by HQL:

Code:

List<StaffSchedule> staffScheduleList = session.createCriteria(StaffSchedule.class)
                     .add(Restrictions.eq("staffId", staffId)).list();
select
        this_.id as id6_0_,
        this_.staffId as staffId6_0_,
        this_.startDate as startDate6_0_,
        this_.endDate as endDate6_0_
    from
        TC_StaffSchedule this_ 
    where
        this_.staffId=?

shynate26 · **Posted:** Tue Aug 10, 2010 7:00 am

Hi Suomi99,

Whether the problem resolved or still you get property violation error?

By default if many-to-one is specified hibernate looks at the identifier column , which is unique in the table. Only when it is referenced other than primary key property-ref can be used. Else we can ignore that attribute.

Saeed · **Joined:** Sat Nov 19, 2005 11:54 am **Posts:** 22

you can Also solve problem by this code if you don`t want to use HQL:

Code:

Criteria c=session.createCriteria(StaffSchedule.class);
c.createAlias("staffId","staffId");
List<Map> mapList= c.setResultTransformer(Transformers.aliasToBean(Staff.class)).list();

now you can Iterate in mapList and access to Staff by "staffId" key
but i suggest you HQL

suomi99 · **Joined:** Mon Aug 09, 2010 3:39 pm **Posts:** 7

Nordborg, thanks for your response. I understand the problem now.

The class definition for StaffSchedule returns the PK of Staff and not the Staff object itself. And I cannot change this because we are trying to replace Hibernate with another home grown solution

Code:

public class StaffSchedule implements Serializable {
   // the PK of the schedule
   protected long id;
   // the FK to the staff owning this schedule
   protected long staffId;
   // the date from when the schedule starts. null if it starts from now.
   protected Date startDate;   
   // the date till when the schedule is applicable.
   protected Date endDate;
}

So, I think I need to correct my many-to-one association. My current many-to-one association is shown below. How can I model it to reflect that the StaffSchedule.getStaffId() returns the the PK for Staff and not the Staff object itself?

Code:

<class name="StaffSchedule" table="TC_StaffSchedule">
.......      
      <many-to-one name="staffId" column="staffId" 
      class="test.Staff" not-null="true"/>
........
/class>

nordborg · **Posted:** Tue Aug 10, 2010 12:34 pm

You can model it as a regular <property>. The drawback with this is that, as far as Hibernate is concerned, there is no longer a many-to-one association between the StaffSchedule and Staff objects. This means that you, for example, can't do joins in queries/criterias, can't use cascading for save/update/delete/etc.., and possible some other limitations as well. Since you are moving away Hibernate, this may not be of any importance to you anyway.

suomi99 · **Joined:** Mon Aug 09, 2010 3:39 pm **Posts:** 7

Thanks nordborg.

I meant we are moving to Hibernate from a home-grown solution, which is why I the data-model exists and cannot be changed. Thanks for your tip mate!

suomi99 · **Joined:** Mon Aug 09, 2010 3:39 pm **Posts:** 7

I have now changed my model so that StaffSchedule.getStaff returns a Staff obect and not a PK of Staff. However I am still getting the same old error.

Code:

public class StaffSchedule implements Serializable {
   // the PK of the schedule
   protected long id;
   // the FK to the staff owning this schedule
   protected Staff staff;   
   // the date from when the schedule starts. null if it starts from now.
   protected Date startDate;   
   // the date till when the schedule is applicable.
   protected Date endDate;
}

Code:

<many-to-one name="staff" column="staff" 
      class="test.Staff" not-null="true"/>

The following lines throw an error:

Code:

List<StaffSchedule> staffScheduleList = session.createCriteria(StaffSchedule.class)
                     .add(Restrictions.eq("staff", staffId)).list();

The error is:

Code:

Service method 'public abstract java.util.List test.StaffSchedulerService.getAllSchedules(long)' threw an unexpected exception: org.hibernate.PropertyAccessException: IllegalArgumentException occurred calling getter of test.Staff.id
.....
Caused by: org.hibernate.PropertyAccessException: IllegalArgumentException occurred calling getter of test.Staff.id
.....
Caused by: java.lang.IllegalArgumentException: object is not an instance of declaring class
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at org.hibernate.property.BasicPropertyAccessor$BasicGetter.get(BasicPropertyAccessor.java:172)
   ... 46 more

Could anything else be the matter?

shynate26 · **Posted:** Wed Aug 11, 2010 12:10 am

You have earlier mapped staffId to colun staffId. But after changing the property to staff, column mapping also changed to staff .

Which is the correct column name staffId or staff ? Check with your schema.

suomi99 · **Joined:** Mon Aug 09, 2010 3:39 pm **Posts:** 7

Thanks for your response shynate26.

I had dropped the database table and recreated it, so, that is not the problem. My Hibernate mapping is as follows:

Code:

<many-to-one name="staff" column="staff" 
      class="test.Staff" not-null="true"/>

My table definition.

Code:

ID   NUMBER(19,0)   No      1   
STAFF   NUMBER(19,0)   No      2   
STARTDATE   DATE   No      3   
ENDDATE   DATE   No      4   