Mapping a composite pattern?

amd700 · **Joined:** Tue Sep 28, 2004 3:16 am **Posts:** 1

Hi everyone,
I have encountered an issue of mapping my domain objects.
I have three classes:

Code:

public abstract class Item extends Entity {
    Item parent;
    String code;

    public Item getParent() {
        return parent;
    }
    
    public void setParent(Item parent) {
        this.parent = parent;
    }
    
    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

}


public class Category extends Item {
    Set<Item> items;
    
    public Category() {
        items = new HashSet<Item>();
    }
    
    public Set<Item> getItems() {
        return items;
    }
    
    public void setItems(Set<Item> items) {
        this.items = items;
    }
    
    public void addItem(Item item) {
        if (item!=null) {
            items.add(item);
            item.setParent(this);
        }
    }
    
    public void removeItem(Item item) {
        if (item!=null) {
            items.remove(item);
            item.setParent(null);
        }
    }
}


public class Product extends Item {
    String unit;
    double salePrice; // VND
    double purchasePrice; // VND
    
    public String getUnit() {
        return unit;
    }
    
    public void setUnit(String unit) {
        this.unit = unit;
    }
    
    public double getPurchasePrice() {
        return purchasePrice;
    }
    
    public void setPurchasePrice(double importPrice) {
        this.purchasePrice = importPrice;
    }
    
    public double getSalePrice() {
        return salePrice;
    }
    
    public void setSalePrice(double sellPrice) {
        this.salePrice = sellPrice;
    }
}

...and I mapped these classes as follow:

Code:

<hibernate-mapping package="com.anant.ejournal.om">   
   <class name="Item" table="ITEM">
        <id
           name="id"
           column="ITEM_ID" 
           type="long"
           unsaved-value="0">
           
            <generator class="native"/>
        </id>
        
        <property
           name="name"
           column="NAME"
           type="string"/>
        
        <property
           name="code"
           column="CODE"
           type="string"/>
           
        <many-to-one
           name="parent"
           class="Item"
           column="PARENT_ID"           
           cascade="none"/>        
    </class>
    
    <joined-subclass name="Category" table="CATEGORY" extends="Item">
       <key column="CATEGORY_ID"/>
       
       <set
          name="items"
          cascade="save-update"
          table="ITEM"
          inverse="true">
          <key column="PARENT_ID"/>
          <one-to-many class="Item"/>
       </set>
    </joined-subclass>
    
    <joined-subclass name="Product" table="PRODUCT" extends="Item">
       <key column="PRODUCT_ID"/>
       
       <property
          name="unit"
          column="UNIT"
          type="string"/>
       
       <property
          name="salePrice"
          column="SALE_PRICE"
          type="double"/>
       
       <property
          name="purchasePrice"
          column="PURCHASE_PRICE"
          type="double"/>
    </joined-subclass>
</hibernate-mapping>

...when I run a sample program as follow:

Code:

        ....
        Category category1 = new Category();
        Category category2 = new Category();
        Product product1 = new Product();
        Product product2 = new Product();
        Product product3 = new Product();

        category1.addItem(category2);
        category1.addItem(product1);
        category2.addItem(product2);
        category2.addItem(product3);
        
        dao.saveOrUpdate(category1);
        ....

...Exception was thrown. Here is the stack trace

Code:

Caused by: org.hibernate.MappingException: Unknown entity: com.anant.ejournal.om.Category
   at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:514)
   at org.hibernate.impl.SessionImpl.getEntityPersister(SessionImpl.java:1302)
   at org.hibernate.engine.ForeignKeys.isTransient(ForeignKeys.java:180)
   at org.hibernate.event.def.AbstractSaveEventListener.getEntityState(AbstractSaveEventListener.java:460)
   at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:84)
   at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
   at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:502)
   at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:494)
   at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:490)
   at org.springframework.orm.hibernate3.HibernateTemplate$16.doInHibernate(HibernateTemplate.java:672)
   at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:361)
   at org.springframework.orm.hibernate3.HibernateTemplate.saveOrUpdate(HibernateTemplate.java:669)
   at com.anant.baseware.dao.hibernate.HibernateDAO.saveOrUpdate(HibernateDAO.java:76)
   at RCMScrapbook.main(RCMScrapbook.java:72)

I dont know if my mapping file is correct. Please help me. Thank you in advance!

I am using Hibernate version: 3.1.3

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

Looks like you have a different mapping referring to Category? You can't do that, you need to refer to Item as it's the base class.

There's another bug in your code. You have inverse="true" on the Category->Item collection, but in your source code you're added transient Items to the collection. This won't work. Either remove inverse="true" (allowing Hibernate to persist the transient items), or save the items before adding them to the collection.