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NullPointerException whith simple many-to-one association

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rainer198

Post subject: NullPointerException whith simple many-to-one association

Posted: Tue Feb 21, 2006 5:19 pm

Newbie

Joined: Tue Feb 21, 2006 4:03 pm
Posts: 10

Hi,

I am a hibernate newbi. Currently, I am trying to read rows from a table "journal". This table has a foreign key link to another table "publisher"
(thus a classical many-to-one association).

Doing so, a NullPointerException is throws.
However, the program works if i delete the many-to-one from the mapping file (naturally iwithout the desired link to a publisher entry).
Thats why i guess that something is wrong with my association mapping or the persistent class object. (or even with the database tables).

Do you have any ideas?

Here the putativly relevant code:

Journal class

Code:

public class Journal{
   public Journal(){}
   private long id;
   private String name;
   /**
    * The Publisher of the journal
    */
   private Publisher publisher = new Publisher();
       // setters and getters
      ...
}

Publisher class

Code:

public class Publisher{
   public Publisher(){}
   private long id;
   private String name;
        priavte String address;
       // setters and getters
      ...
}

Journal mapping

Code:

<class name="Journal" 
          table="journal"
          schema="pblc">
      <id name="id" column="id" type="long">
      <generator class="sequence">
            <param name="sequence">pblc.journal_id_seq</param>
         </generator>
      </id>
      <property name="name" .../>
      <many-to-one  
            name="publisher"
            column="publisher_id"/>
   </class>

PostgreSQL tables

Code:

CREATE TABLE pblc.publisher 
(
   id      SERIAL PRIMARY KEY,
   name   VARCHAR(50),
   address VARCHAR(50) 
);

-- table for a scientific journal
CREATE TABLE pblc.journal
(
   id      SERIAL PRIMARY KEY,
   name    varchar(100),
   publisher_id INTEGER REFERENCES pblc.publisher (id) ON DELETE RESTRICT,
);

And last the first few lines of the error

Quote:

Exception in thread "main" java.lang.NullPointerException
at java.lang.Object.getClass() (/usr/lib/libgcj.so.6.0.0)
at org.hibernate.tuple.AbstractEntityTuplizer.createProxy(java.io.Serializable, org.hibernate.engine.SessionImplementor) (Unknown Source)
at org.hibernate.persister.entity.AbstractEntityPersister.createProxy(java.io.Serializable, org.hibernate.engine.SessionImplementor) (Unknown Source)
at org.hibernate.event.def.DefaultLoadEventListener.createProxyIfNecessary(org.hibernate.event.LoadEvent, org.hibernate.persister.entity.EntityPersister, org.hibernate.engine.EntityKey, org.hibernate.event.LoadEven

[/b]

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rainer198

Post subject:

Posted: Wed Feb 22, 2006 10:31 am

Newbie

Joined: Tue Feb 21, 2006 4:03 pm
Posts: 10

My problem is still unsolved. I tried (i think) everything.
Implementing hashCode() and equals(),
Deleted the foreign key constraint in the database,
called the no-argument-constructor of "Publisher"
in the Journal-class and so on..

Do anyone have a great idea?

Thanx,
Rainer.

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mnkaushik

Post subject:

Posted: Wed Feb 22, 2006 11:00 am

Newbie

Joined: Tue Feb 21, 2006 6:43 pm
Posts: 4

Try this

<many-to-one
name="publisher"
class="Publisher"
column="publisher_id"/>

and in your Journal Class just have

private Publisher publisher

and have getter and setter for it.

In your mapping u have to mention the class your using.

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rainer198

Post subject:

Posted: Wed Feb 22, 2006 11:35 am

Newbie

Joined: Tue Feb 21, 2006 4:03 pm
Posts: 10

thank you, but it still does not work.

Look at my code, there still was a private Publisher attribute
in Journal. And mentioning the class was one thing I tried before
and now again, without any effect.

Bye,
Rainer.

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rainer198

Post subject:

Posted: Wed Feb 22, 2006 1:59 pm

Newbie

Joined: Tue Feb 21, 2006 4:03 pm
Posts: 10

I had a look at previous log4-messages (previous to the shitty NullPointerException.

It turns out that for every persistent class there is a
message like
12219 [main] ERROR org.hibernate.proxy.BasicLazyInitializer - CGLIB

Quote:

Enhancement failed: zenodot.database.entities.Journal
java.lang.NoClassDefFoundError: net.sf.cglib.proxy.Enhancer
at java.lang.Class.initializeClass() (/usr/lib/libgcj.so.6.0.0)
at org.hibernate.proxy.CGLIBLazyInitializer.getProxyFactory(java.lang.Class, java.lang.Class[]) (Unknown Source)
at org.hibernate.proxy.CGLIBProxyFactory.postInstantiate(java.lang.String, java.lang.Class, java.util.Set, java.lang.reflect.Method, java.lang.reflect.Method, org.hibernate.type.AbstractComponentType) (Unknown Source)
at org.hibernate.tuple.PojoEntityTuplizer.buildProxyFactory(org.hibernate.mapping.PersistentClass, org.hibernate.property.Getter, org.hibernate.property.Setter) (Unknown Source)
at org.hibernate.tuple.AbstractEntityTuplizer.AbstractEntityTuplizer(org.hibernate.tuple.EntityMetamodel, org.hibernate.mapping.PersistentClass) (Unknown Source)
at org.hibernate.tuple.PojoEntityTuplizer.PojoEntityTuplizer(org.hibernate.tuple.EntityMetamodel, org.hibernate.mapping.PersistentClass) (Unknown Source)
at org.hibernate.tuple.TuplizerLookup.create(org.hibernate.mapping.PersistentClass, org.hibernate.tuple.EntityMetamodel) (Unknown Source)
at org.hibernate.tuple.EntityMetamodel.EntityMetamodel(org.hibernate.mapping.PersistentClass, org.hibernate.engine.SessionFactoryImplementor) (Unknown Source)
at org.hibernate.persister.entity.AbstractEntityPersister.AbstractEntityPersister(org.hibernate.mapping.PersistentClass, org.hibernate.cache.CacheConcurrencyStrategy, org.hibernate.engine.SessionFactoryImplementor) (Unknown Source)
at org.hibernate.persister.entity.SingleTableEntityPersister.SingleTableEntityPersister(org.hibernate.mapping.PersistentClass, org.hibernate.cache.CacheConcurrencyStrategy, org.hibernate.engine.SessionFactoryImplementor, org.hibernate.engine.Mapping) (Unknown Source)
at org.hibernate.persister.PersisterFactory.createClassPersister(org.hiberna

It seems that there is no net.sf.cglib.proxy.Enhancer.

However, there is such a class in cglib-2.1.3.jar which I have in my class path.

How that comes?

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