Error while trying to get data from Master-Detail tables

[Juan Carlos]

Hi,
I am pretty new to Hibernate and needs some help in resolving the following issue. I am trying to retrieve Menu and SubMenus data from
Database tables. I have two tables Menu and SubMenu. I can save the data fine. But when trying to get the data I get errors. How can I query on the Menu table to give me all the data in that table along with
data in the SubMenus table. Following are the hbm.xml files.

 
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="HiberSubMenu" table="Hiber_CHILD_MENU">
        <id name="id" column="SUB_MENU_ID" type="long">
            <generator class="sequence">
            <param name="sequence">Hiber_SUB_MENU_SEQ</param>
        </generator>
        </id>
<many-to-one name="HiberMenu" class="HiberMenu">
        <column name="MENU_ID" />
    </many-to-one>
<property name="subMenuTitle" type="string"  length="50" column="SUB_MENU_TITLE"/>
<property name="subMenuUrl" type="string"  length="250" column="SUB_MENU_URL"/>
<property name="subMenuActive" type="string"  length="1" column="SUB_MENU_ACTIVE"/>        
<property name="createdDate" type="timestamp" column="CREATED_DATE"/>
    <property name="createdBy" type="string"  length="35" column="CREATED_BY"/>
    </class>
</hibernate-mapping>
 
/********************************************/
 
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="HiberMenu" table="Hiber_PARENT_MENU">
        <id name="id" column="MENU_ID" type="long">
            <generator class="sequence">
            <param name="sequence">Hiber_MENU_SEQ</param>
        </generator>
        </id>
<property name="menuTitle"  type="string"  length="50" column="MENU_TITLE" not-null="true"/>
<property name="menuUrl"  type="string"  length="250" column="MENU_URL" not-null="true"/>
<property name="menuActive"  type="string"  length="1" column="MENU_ACTIVE" not-null="true"/>
    <property name="subMenuFlag"  type="string"  length="1" column="SUB_MENU_FLAG" not-null="true"/>
<property name="createdDate" type="timestamp"  column="CREATED_DATE" not-null="true"/>
    <property name="createdBy"  type="string"  length="35" column="CREATED_BY" not-null="true"/>
 
<set name="subMenu" inverse="true" cascade="all">
            <key>
                <column name="MENU_ID"/>
            </key>
            <one-to-many class="HiberSubMenu" />
        </set>
 
    </class>
 
</hibernate-mapping>

Code that handles the save part

Session session = HibernateUtil.currentSession();
Transaction tx = session.beginTransaction();
           
HiberMenu ac = new HiberMenu();
ac.setCreatedBy("Admin");
ac.setMenuTitle("ABOUT US");
ac.setCreatedDate(new Date());
ac.setMenuActive("1");
ac.setSubMenuFlag("1");
ac.setMenuUrl("http://www.cnn.com");
      
Set adding = new HashSet();
for(int i = 0; i < 3; i++)
{
   HiberSubMenu acs = new HiberSubMenu();
   acs.setCreatedBy("User " + i);
   acs.setCreatedDate(new Date());
   acs.setSubMenuActive("1");
   acs.setSubMenuTitle("NEW TITLE " + i);
   acs.setSubMenuUrl("Any URL goes here");
   acs.setHiberMenu(ac);
   adding.add(acs);
}      
ac.setSubMenu(adding);
Long id = (Long)session.save(ac);
tx.commit();
hsqlCleanup(session);
HibernateUtil.closeSession();
...
...

Here I am trying to get the saved data, but it throws an error when trying to get the SubMenus for a Menu

Session session = HibernateUtil.currentSession();
Transaction tx = session.beginTransaction();
List result = session.createQuery("from HiberMenu").list();
tx.commit();
hsqlCleanup(session);
HibernateUtil.closeSession();
 
for (int i = 0; i<menus.size(); i++) 
{
  HiberMenu theHiberParentMenu = (HiberMenu) menus.get(i);
  
  //means current menu has submenus, so get those too
  if(theHiberParentMenu.getSubMenuFlag().equalsIgnoreCase("1"))
  {
    Set submenus = theHiberParentMenu.getSubMenu();
    //gives me the following error here
    Iterator iter = submenus.iterator();
  }
}
 
...
....
 

Here is the error I am getting

ERROR - failed to lazily initialize a collection (de.gloegl.road2hibernate.HiberMenu.subMenu) - no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection (de.gloegl.road2hibernate.HiberMenu.subMenu) - no session or session was closed
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:179)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:47)
at org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:133)
at de.gloegl.road2hibernate.EventManager.main(EventManager.java:32)
Exception in thread main
org.hibernate.LazyInitializationException: failed to lazily initialize a collection (de.gloegl.road2hibernate.HiberMenu.subMenu) - no session or session was closed
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:179)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:47)
at org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:133)
at de.gloegl.road2hibernate.EventManager.main(EventManager.java:32)

How to get all the data from Master and detail table while querying on Master table. Any help is appreciated. Thanks

[Mark Spritzler]

"White Sox"

Please click on the My Profile Link above and change your display name to meet the JavaRanch Naming Policy of using your real first and real last names.

Thanks

Mark

[Mark Spritzler]

OK, so here

HibernateUtil.closeSession();
 
for (int i = 0; i<menus.size(); i++) 

you close the Session, then after that try to get the child data. But the CHild data is lazy loaded, meaning when you first get the Parent object, the children Collection in it is not loaded, it is empty. It is when you get the Collection and start going through it that Hibernate will get the data, but you closed the session, so Hibernate can't get the data.

So either 1. Set lazy loading to false, or 2. don't close the session till after you have read everything.

And remember to change your display name.


Mark

[Juan Carlos]

Thanks, getting all the data before closing the session worked.

[Juan Carlos]

I have one more issue and any help is appreciated. How can I keep the order of my detail records i.e. Sub Menus keep changing there order as I want them to show in same order. Right now everytime I refresh the page Sub Menus order keeps changing. Any help is appreciated. Thanks