Question

I’m trying to build a 4-tier Web-Application in Java. I’m using the Hibernate Framework for ORM and a MySQL Database.
The table “project” has a one-to-many relation to the table “idea”. What I’m trying to do, is to get a List (or Set) of Ideas using the following function:

public static List getProjectIdeas(int projectId)
    {
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        session.beginTransaction();
        Query q = session.createQuery("from Idea where id_project=" + projectId);
        List<Idea> ideaList = (List<Idea>) q.list();
        System.out.println(ideaList.size());
        return ideaList;
    }

At first, it works fine and I get all the ideas from the database. But when I add new ideas to the project and then call the function again, I don’t always get a complete list of the ideas related to the project back. The size of the list I receive from q.list() varies between the number of ideas stored in the database before the insert and the actual number of ideas.
This is the function I use to insert the Idea into the Database:

public static void writeObject(Object object)
    {
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        Transaction tx = session.beginTransaction();
        session.saveOrUpdate(object);
        tx.commit();
    }  

This is my first hibernate project, so i don’t know if there is anything wrong with the config file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">***/ideator</property>
    <property name="hibernate.connection.username">***</property>
    <property name="hibernate.connection.password">***</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="hibernate.query.factory_class">org.hibernate.hql.classic.ClassicQueryTranslatorFactory</property>
    <mapping resource="mapping/Category.hbm.xml"/>
    <mapping resource="mapping/Rating.hbm.xml"/>
    <mapping resource="mapping/Idea.hbm.xml"/>
    <mapping resource="mapping/Participation.hbm.xml"/>
    <mapping resource="mapping/Project.hbm.xml"/>
    <mapping resource="mapping/Criteria.hbm.xml"/>
    <mapping resource="mapping/User.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

Thanks in advance for you help.

Answer 1

Ok, I was able to fix the bug. Apparently, it was not a good idea to use getCurrentSession. Better manage the session by yourself:

Session session = HibernateUtil.getSessionFactory().openSession();
       Transaction tx = null;
       Idea idea = null;

       try {
           tx = session.beginTransaction();
           idea = (Idea) session.get(Idea.class, id);
           tx.commit();
       } catch (Exception e) {
           if(tx != null) {
               tx.rollback();
           }
       } finally {
           session.flush();
       }

       return idea;

Case closed.