Hi

Can someone help please?
I have a connection to my Posrgresql database.
How do i display the data that is contained in my list?
the part in bold does not work and give the error:

log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: select name from NAMES
Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object;
at hello.HelloWorld.main(HelloWorld.java:25)
5 message(s) found:

//this is part of my code.
Session newSession =HibernateUtil.currentSession ().getSessionFactory().openSession();
Transaction newTransaction = newSession.beginTransaction();
List messages = newSession.createSQLQuery("select name from NAMES").list();

//this tells me that my query found n items in the table
System.out.println( messages.size() + " message(s) found:" );

for ( Iterator iter = messages.listIterator();iter.hasNext(); )
{
NAMES loadedMsg = (NAMES) iter.next();
System.out.println( loadedMsg.getText() );
}
newTransaction.commit();
newSession.close();


//this is my NAMES class

package hello;

public class NAMES {
private long id;
private String text;
private NAMES nextMessage;

NAMES()
{

}

public NAMES(String text)
{
this.text = text;
}

public Long getId()
{
return id;
}

private void setId(Long id)
{
this.id = id;
}

public String getText()
{
return text;
}

public void setText(String text)
{
this.text = text;
}

public NAMES getNextMessage()
{
return nextMessage;
}

public void setNextMessage(NAMES nextMessage)
{
this.nextMessage = nextMessage;
}


}

Which line in your code does the exception point to? The exception says
(HelloWorld.java:25), but which line is that?


I don't know if this will help you, but in my code i use an iterator :

for (Iterator iter = messages.iterator(); iter.hasNext();)


In your code, you have a listIterator:

for (Iterator iter = messages.listIterator(); iter.hasNext();)


regards,
Mark

Hi Mark

this is the main class. i tried the changing ListIterator to just iterator but the problem still persists.

the problem:
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: select name from names
2 message(s) found:
Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object;
at hello.HelloWorld.main(HelloWorld.java:28)


package hello;

import java.util.*;

import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.util.*;
import org.hibernate.Session;
import java.util.logging.*;
import org.hibernate.dialect.PostgreSQLDialect;
import java.sql.*;



//import persistence.*;
public class HelloWorld {
public static void main(String[] args) {
// First unit of work

Session newSession =HibernateUtil.currentSession().getSessionFactory().openSession();
Transaction newTransaction = newSession.beginTransaction();
List messages = newSession.createSQLQuery("select name from names").list();

System.out.println( messages.size() + " message(s) found:" );

for ( Iterator iter = messages.iterator();iter.hasNext(); )
{
NAMES loadedMsg = (NAMES) iter.next();
System.out.println( loadedMsg.getText() );
}
newTransaction.commit();
newSession.close();

// Shutting down the application
HibernateUtil.closeSession();
}
}

Ok. I see the problem now.

The problem is in your query.

List messages = newSession.createSQLQuery("select name from NAMES").list();

First, is there a reason you a creating an SQLQuery and not HQL?
I don't think your query is returning NAMES entities.


You should try this code which uses HQL:

List messages = newSession.createQuery(from NAMES").list();

This will return a List of NAMES entities



If you really need to use SQLQuery, then you need to do something like this:
List messages = newSession.createSQLQuery("select * from NAMES").addEntity("NAMES", NAMES.class ).list();

Hi

thanks firstly. i tried the HQL and it return my data.
there is no reason for using the SQL opposed to HQL. i just it is better.
is there an advantage of using hql

if i use the SQL and i changed mine to use :
List messages = newSession.createSQLQuery("select * from NAMES").addEntity("NAMES", NAMES.class ).list();

i get the error:

log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: select * from NAMES
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not execute query
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:59)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.doList(Loader.java:1502)
at org.hibernate.loader.Loader.list(Loader.java:1482)
at org.hibernate.loader.custom.CustomLoader.list(CustomLoader.java:103)
at org.hibernate.impl.SessionImpl.listCustomQuery(SessionImpl.java:1333)
at org.hibernate.impl.SQLQueryImpl.list(SQLQueryImpl.java:146)
at hello.HelloWorld.main(HelloWorld.java:23)
Caused by: org.postgresql.util.PSQLException: The column name nameid0_ was not found in this ResultSet.
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.findColumn(AbstractJdbc2ResultSet.java:2450)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.getLong(AbstractJdbc2ResultSet.java:2317)
at org.hibernate.type.LongType.get(LongType.java:26)
at org.hibernate.type.NullableType.nullSafeGet(NullableType.java:77)
at org.hibernate.type.NullableType.nullSafeGet(NullableType.java:68)
at org.hibernate.loader.Loader.getKeyFromResultSet(Loader.java:650)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:277)
at org.hibernate.loader.Loader.doQuery(Loader.java:384)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:203)
at org.hibernate.loader.Loader.doList(Loader.java:1499)
... 5 more

This from the Hibernate documentation on HQL:
http://www.hibernate.org/hib_docs/v3/re ... ryhql.html

Hibernate is equipped with an extremely powerful query language that (quite intentionally) looks very much like SQL. But don't be fooled by the syntax; HQL is fully object-oriented, understanding notions like inheritence, polymorphism and association.

for the hibernate documentation on using SQL instead of HQL:
http://www.hibernate.org/hib_docs/v3/re ... rysql.html


I would only use SQL if there is something you can't do with HQL.

regards,
Mark

ok thanks for the resource links.
i really appreciate your help.

Cheers Avesh