I get following error :

Hibernate: insert into EVENTS (EVENT_DATE, TITLE) values (?, ?)
org.hibernate.exception.ConstraintViolationException: could not insert: [events.Event]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:69)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:1986)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2405)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:37)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:243)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:269)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:167)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:101)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:186)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:175)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:544)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:533)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:529)
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:324)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:292)
at $Proxy0.save(Unknown Source)
at events.EventManager.createAndStoreEvent(Unknown Source)
at events.EventManager.main(Unknown Source)
Caused by: java.sql.SQLException: ORA-01400: cannot insert NULL into ("DAWEB_USER"."EVENTS"."EVENT_ID")

at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:168)
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:208)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:543)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1405)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:822)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:1446)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:1371)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1900)
at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:363)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:1976)
... 22 more
Exception in thread "main"

Is that something to do with the generator class ? Please help me out ..

Thanks.

yes, it's attempting to insert a NULL value into a table that has NOT NULL set for the column it's trying to insert into.
As your generator seems to not be working you're likely seeing a side effect of that (the value would be NULL until after the generator returns a real value to use instead).

so, what should I do for correcting this ? am not clear



Thanks,

Hi:
Check the generator class in your Event.hbm.xml that is suitable to your needs. You should read http://www.hibernate.org/hib_docs/refer ... pping.html in section 5.1.4.1. Generator. As I see in your stack trace you are using Oracle as DBMS.

For example for my non-clustered DB2 database
In my Event.hbm.xml:


And create the database sequence object:



Hope Its usefull