I'm new to Hibernate and am having some very serious problems trying to do something which is *very* simple in basic SQL code - join two tables together in a one-to-many relationship.
I've got two objects w/ a "one-to-many" parent/child association, real simple stuff. I am trying to select the parent and automatically select the children - all of this is defined in the two mapping *.hbm.xml files of the two classes - all cobbled together from the Hibernate doucmentation and the examples found in Hibernate in action, which I purchased last week.
Anyhow, here are my two classes. AttributeCategory is the parent and Attribute is the child - an AttributeCategory can have many Attributes...which is defined as a List in the AttributeCategory class...see below:
Code:
package com.agribeef.bol;
/**
* @author vjenks
*
*/
public class Attribute implements IAttribute
{
private int _id;
private int _categoryID;
private IAttributeCategory _category;
private String _name;
private String _contents;
/**
*
*/
public Attribute()
{
// TODO Auto-generated constructor stub
}
public IAttributeCategory getCategory()
{
return this._category;
}
public void setCategory(AttributeCategory category)
{
this._category = category;
}
public int getCategoryID()
{
return this._categoryID;
}
public void setCategoryID(int categoryID)
{
this._categoryID = categoryID;
}
public String getContents()
{
return this._contents;
}
public void setContents(String contents)
{
this._contents = contents;
}
public int getID()
{
return this._id;
}
public void setID(int id)
{
this._id = id;
}
public String getName()
{
return this._name;
}
public void setName(String name)
{
this._name = name;
}
}
Code:
package com.mycompany.bol;
import java.util.List;
public class AttributeCategory
{
private int _id;
private int _directoryID;
private String _category;
private List<Attribute> _attributes;
public AttributeCategory()
{
}
public String getCategory()
{
return this._category;
}
public void setCategory(String category)
{
this._category = category;
}
public int getDirectoryID()
{
return this._directoryID;
}
public void setDirectoryID(int directoryid)
{
this._directoryID = directoryid;
}
public int getID()
{
return this._id;
}
public void setID(int id)
{
this._id = id;
}
public List<Attribute> getAttributes()
{
return this._attributes;
}
public void setAttributes(List<Attribute> attributes)
{
this._attributes = attributes;
}
}
Here are my AttributeCategory and Attribute hbm.xml files, respectively:
Code:
<?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="com.agribeef.bol.Attribute"
proxy="com.agribeef.bol.Attribute"
table="ed_attribute">
<id name="ID" column="attribute_id" type="int" unsaved-value="0">
<generator class="identity"/>
</id>
<property name="CategoryID" column="attribute_category_id"/>
<property name="Name" column="name"/>
<property name="Contents" column="contents"/>
<many-to-one
name="Category"
cascade="save-update"
class="com.agribeef.bol.AttributeCategory"
lazy="false"
insert="false"
update="false"
column="attribute_category_id" />
</class>
</hibernate-mapping>
Code:
<?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="com.agribeef.bol.AttributeCategory"
proxy="com.agribeef.bol.AttributeCategory"
table="ed_attribute_category">
<id name="ID" column="attribute_category_id" type="int" unsaved-value="0">
<generator class="identity"/>
</id>
<property name="DirectoryID" column="directory_id"/>
<property name="Category" column="category"/>
<list
name="Attributes"
table="ed_attribute"
inverse="true"
lazy="true"
cascade="all-delete-orphan">
<key column="attribute_category_id" />
<index column="directory_id" />
<one-to-many class="com.agribeef.bol.Attribute" />
</list>
</class>
</hibernate-mapping>
My call to retrieve a list of AttributeCategory objects (with nested Attribute lists in each) is too dispersed amongst app layers to provide all the code but rest assured, I'm able to call unrelated lists just fine the same way - I'm only getting an error when trying to go beyond a single map-to-class in the mapping files. The error I'm getting is:
Code:
15:14:16,702 ERROR LazyInitializationException:19 - failed to lazily initialize a collection of role: com.agribeef.bol.AttributeCategory.Attributes - no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.agribeef.bol.AttributeCategory.Attributes - no session or session was closed
The session is most definitely not closed - like I said, I'm using the same boilerplate HibernateUtil from Caveat Emptor all over this application and it works fine as long as I'm only mapping one class to one mapping file...this is the only case I get a "session closed" problem.
Please point out what I've done wrong here, I can't spend another 8 hours (at it for 3 days now) trying to figure out how to simply map a parent/child relationship together...and I'm mentally spent.
Thanks everybody, I appreciate the help!
Hibernate version: 3.0.5
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