Class Casting Exception with Hibernate Named Queries

ambika_devi · **Joined:** Mon Oct 01, 2007 8:21 am **Posts:** 40

Hi,

I tried with the hibernate named queries, it is working fine if i use one single table to retrive the data.

If i use more than table to compare and get the query result it is returning the general java.lang.object.

So, i tried casting the general to the specific class which i need but that object returns the combination of both the classes, so casting is not happening, so is there any to handle this situation.

Sample code which i tried,

event.hbm.xml

Code:

<hibernate-mapping>
    <class name="com.gpj.gl.pa.domain.Event" table="O_EVENT_TX" schema="GL_PA">
        <id name="paEventId" type="string">
            <column name="PA_EVENT_ID" length="15" />

            <generator class="assigned" />
        </id>

        <many-to-one name="eventDb" class="com.gpj.gl.pa.domain.EventDb" fetch="select">
            <column name="GENERIC_EVENT_ID" length="15" not-null="true" />
        </many-to-one>

<query name="myEventSearchByCriteriaOR"><![CDATA[
       from EventDb as eventDB, Event as event
       where event.eventDb.genericEventId = eventDB.genericEventId and
          (event.eventDb.eventName = :eventName
           or event.eventDb.eventYear =:eventYear
             or event.eventDb.eventType.eventTypeId =:eventType
           or event.eventDb.countryCd =:eventCountry
           or event.eventDb.stateCd =:eventState
           or event.eventDb.eventCity =:eventCity)
     ]]></query>
</hibernate-mapping>

EventDaoImpl.java

Code:

   public List<Event> findSearchResult(String eventName, String eventYear, String eventType, String eventCountry, String eventState, String eventCity) {
      // TODO Auto-generated method stub
      List<Event> searchResult = null;
      String queryName = null;
      String[] argNames = null;
      Object[] args = null;
      
      if(!eventName.equals("") || !eventYear.equals("") 
            || !eventType.equals("") || !eventCountry.equals("") 
            || !eventState.equals("") || !eventCity.equals("")){

         queryName = "myEventSearchByCriteriaOR";
         argNames = new String[] { "eventName", "eventYear", "eventType",
               "eventCountry", "eventState", "eventCity" };
         args = new Object[] { eventName, eventYear,
               eventType, eventCountry, eventState, eventCity };

         searchResult = new ArrayList<Event>( getHibernateTemplate()
               .findByNamedQueryAndNamedParam(queryName, argNames, args));
         System.out.println("Generic Id DAO: "+ searchResult.size());
         
         System.out.println("Generic Id DAO: "+ searchResult.toString());
         
         for(int i=0; i<searchResult.size();i++){
            Event evt = (Event) searchResult.get(i);
            System.out.println("Generic Id DAO: "+ evt.getEventDb().getGenericEventId());
            System.out.println("PA ID "+evt.getPaEventId());   
         }
      }
      return searchResult;
   }
}

I would like to get the object of Event Class rather than general Object class or EventDb class.
below is the picture of searchResult object while debugging.

Quote:

searchResult ArrayList<E> (id=173)
elementData Object[2] (id=188)
[0] Object[2] (id=4955)
[0] EventDb (id=4965)
[1] Event (id=4964)
[1] Object[2] (id=4956)
[0] EventDb (id=4965)
[1] Event (id=4983)
modCount 0
size 2

Exception:

Quote:

Generic Id DAO: 2
Generic Id DAO: [[Ljava.lang.Object;@b3951d, [Ljava.lang.Object;@2cf63]
Jun 25, 2008 10:54:13 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet pa threw exception
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.gpj.gl.pa.domain.Event
at com.gpj.gl.pa.dao.impl.EventDaoImpl.findSearchResult(EventDaoImpl.java:75)
at com.gpj.gl.pa.service.impl.MyEventServiceImpl.findEventsByCreteria(MyEventServiceImpl.java:58)
at com.gpj.gl.pa.web.controller.SearchMyEventFormAction.myEventSearch(SearchMyEventFormAction.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)

amersohail794 · **Joined:** Wed Sep 21, 2005 8:18 am **Posts:** 31

Change and replace your hql as follows:

from Event as event
where
event.eventDb.eventName = :eventName
or event.eventDb.eventYear =:eventYear
or event.eventDb.eventType.eventTypeId =:eventType
or event.eventDb.countryCd =:eventCountry
or event.eventDb.stateCd =:eventState
or event.eventDb.eventCity =:eventCity

Since Event contains EventDB and you want to retrieve object of event, so just write Event in from clause. In where condition, when you write event.eventDb.everntName, it automcatically makes a equijoin of Event with eventDB, so you don't need to do anything special.

Cameron McKenzie · **Posted:** Wed Jun 25, 2008 10:18 am

amersohail794's advice should work

Sometimes it's interesting to do a .getClass() method on the object being returned, so you can actually see the true class being returned to your query. Sometimes it's more than just an Object, but perhaps, an instance of a different class in your domain model.

Just helpful little troubleshooting tip.

shagufta · **Joined:** Fri May 22, 2009 4:50 am **Posts:** 59

hi ambika,

I met the same problem. Adding <return> tag to <sql-query> colved my problem. Try adding this to your mapping file.
<return alias="event" class="com.gpj.gl.pa.domain.Event"/>

Shagufta