Plea for example - Many-to-Many CMP EJB

Question

I am attempting to create an EJB that uses Container Managed Persistence,
but my situation seems to be an odd one. The EJB needs to have a
Many-to-Many relationship to itself, because the object is Hierarchical.
Because this is my first EJB I am having a hard time with all of the
deployment descriptors.
I am asking for an example of any Many-to-Many EJB relationship that uses
Weblogic's built-in link table creation to make the relationship (that
works). I realize that there are confidentiality issues with many people
releasing code. I will make any promise (short of selling my soul) that the
code will be safe and promply destroyed immediately after inspection.
Thanks for any help,
Tom
[email protected]

Answer 1

The following describes how to establish a self many-to-many relationship with regards to Product having many parent products and many children products. I have attached the example files as well. Most of these files were generated using EJBGen. I would highly recommend it...
EJB
v Navigating from a Product to its parent Products results in getParents() method in Product
§ Since a Product can have many parents the return type of getParents() method is
java.util.Collection
§ Calling setParents() method results in establishing the new links between this Parent and
parent Products
§ Adding a Product as Parent to the Product results in establishing a new link between this
Product and other Product as parent
· This product is made available in the collection of children in the other Product
§ Removing a Product as Parent to the Product results in breaking a link between this
Product and the other Product as parent
· This product is also removed from the collection of children in the other Product
v Navigating from a Product to its children Products results in getChildren() method in Product
§ Since a Product can have many children the return type of getChildren() method is
java.util.Collection
§ Calling setChildren() method results in breaking the old links between this Product and
children Products
§ Adding a Product as child to the Product results in establishing a new link between this
Product and other Product as child
· This product is made available in the collection of parents in the other Product
§ Removing a Product as child from the Product results in breaking a link between this
Product and the other Product as child
· This Product is also removed from the collection of parents in the other Product.
v Example: ProductBean
Ø DataBase
v For a many-to-many relationship define a new associative (join) table
v Define a new Parent_Child_Product associative table
v The Parent_Child_Product has compound primary keys: Parent_Product_ID and
Child_Product_ID
v Parent_Product_ID and Child_Product_ID are foreign keys to Product table
v Example: Product, Parent_Child_Product
Ø Deployment Descriptors
v ejb-jar.xml
§ Within <ejb-jar>.<relationships>.<ejb-relation> define the following:
· Name of the relationship
o Example: <ejb-relation-name>Parent-Product-Children</ejb-relation-name>
· Role from the parent Product side
o Source
§ Example:
<relationship-role-source>
<ejb-name>Product</ejb-name>
</relationship-role-source>
o Role name
§ Example: <ejb-relationship-role-name>many-Product@children-Have-Product</
ejb-relationship-role-name>
o Multiplicity
§ Example: <multiplicity>many</multiplicity>
o CMR field
§ Example:
<cmr-field>
<cmr-field-name>children</cmr-field-name>
<cmr-field-type>java.util.Collection</cmr-field-type>
</cmr-field>
· Role from the child Product side
o Source
§ Example:
<relationship-role-source>
<ejb-name>Product</ejb-name>
</relationship-role-source>
o Role name
§ Example: <ejb-relationship-role-name>many-Product@parents-Have-Product</
ejb-relationship-role-name>
o Multiplicity
§ Example: <multiplicity>many</multiplicity>
o CMR field
§ Example:
<cmr-field>
<cmr-field-name>parents</cmr-field-name>
<cmr-field-type>java.util.Collection</cmr-field-type>
</cmr-field>
v weblogic-ejb-jar.xml
v weblogic-cmp-rdbms-jar.xml
§ Within <weblogic-rdbms-jar>.<weblogic-rdbms-relation> specify the following:.23
· Name of the relationship matching the name in ejb-jar
o Example: <ejb-relation-name> Parent-Product-Children</ejb-relation-name>
· Specify the name of the joint table
o Example: <table-name> Parent_Child_Product</table-name>
· Specify the mapping using <weblogic-relationship-role>
o Specify the role name matching the name in the ejb-jar
§ Example: <relationship-role-name>many-Product@children-Have-Product</
relationship-role-name>
o Define <relationship-role-map> that defines the mapping of the foreign key to
the primary key mapping
§ Example:
<relationship-role-map>
<column-map>
<foreign-key-column>Parent_Product_ID</foreign-key-column>
<key-column>Product_ID</key-column>
</column-map>
</relationship-role-map>
· Specify the mapping using <weblogic-relationship-role>
o Specify the role name matching the name in the ejb-jar
§ Example: <relationship-role-name> many-Product@parents-Have-Product</
relationship-role-name>
o Define <relationship-role-map> that defines the mapping of the foreign key to
the primary key mapping
§ Example:
<relationship-role-map>
<column-map>
<foreign-key-column>Child_Product_ID</foreign-key-column>
<key-column>Product_ID</key-column>
</column-map>
</relationship-role-map>
"Thomas A. Valletta" <[email protected]> wrote in message news:[email protected]...
I am attempting to create an EJB that uses Container Managed Persistence,
but my situation seems to be an odd one. The EJB needs to have a
Many-to-Many relationship to itself, because the object is Hierarchical.
Because this is my first EJB I am having a hard time with all of the
deployment descriptors.
I am asking for an example of any Many-to-Many EJB relationship that uses
Weblogic's built-in link table creation to make the relationship (that
works). I realize that there are confidentiality issues with many people
releasing code. I will make any promise (short of selling my soul) that the
code will be safe and promply destroyed immediately after inspection.
Thanks for any help,
Tom
[email protected]
[att1.html]
[ejb-jar.xml]
[weblogic-cmp-rdbms-jar.xml]
[weblogic-ejb-jar.xml]
[ProductBean.java]
[ProductLocal.java]
[ProductLocalHome.java]