From: Greg Ederer <greg_at_ergonosis.com>
Date: Thu, 06 Sep 2007 16:53:46 -0700

Hi Markus and Marina,

I now have:

   @ManyToMany
   @JoinTable(
          name="parent_child_category",
          joinColumns=_at_JoinColumn(name="parent_id",
referencedColumnName="id"),
          inverseJoinColumns=_at_JoinColumn(name="child_id",
referencedColumnName="id")
   )
   private List<ToyCategory> parentCategories = new
ArrayList<ToyCategory>();

   @ManyToMany(mappedBy = "parentCategories")
   private List<ToyCategory> childCategories = new
ArrayList<ToyCategory>();

Now, with test data:

   <table name="toy_category">
    <column>id</column>
    <column>name</column>
    <column>description</column>
    <row>
      <value>1</value>
      <value><![CDATA[Toy Vehicles]]></value>
      <value><![CDATA[Toy Vehicles]]></value>
    </row>
    <row>
      <value>2</value>
      <value><![CDATA[Toy Aircraft]]></value>
      <value><![CDATA[Toy Aircraft]]></value>
    </row>
    <row>
      <value>3</value>
      <value><![CDATA[Toy Planes]]></value>
      <value><![CDATA[Toy Planes]]></value>
    </row>
  </table>
  <table name="parent_child_category">
    <column>parent_id</column>
    <column>child_id</column>
    <row>
      <value description="parent_id">1</value>
      <value description="child_id">2</value>
    </row>
    <row>
      <value description="parent_id">2</value>
      <value description="child_id">3</value>
    </row>
  </table>

my tests give me:

   INFO - ToyCategoryDaoTest.testGetToyCategory(20) | Got ToyCategory:
Toy Aircraft
   INFO - ToyCategoryDaoTest.testGetToyCategory(27) | Parents: Toy
Planes |
   INFO - ToyCategoryDaoTest.testGetToyCategory(34) | Children: Toy
Vehicles |

My parents and children seem to be swapped. Not sure what I'm doing wrong.

Thanks!

Greg

Markus Fuchs wrote:
> Hi Greg,
>
> please try this:
>
> @Entity
> public class Category
> {
> @Id
> @Column(name="CATEGORY_ID")
> private Long id;
>
> protected String name;
>
> @ManyToMany
> @JoinTable(
> name="PARENT_CHILD_CATEGORY",
> joinColumns=_at_JoinColumn(name="PARENT_ID",
> referencedColumnName="CATEGORY_ID")
> inverseJoinColumns=_at_JoinColumn(name="CHILD_ID",
> referencedColumnName="CATEGORY_ID")
> )
> protected List<Category> parentCategories = new ArrayList<Category>();
>
> @ManyToMany(mappedBy="parentCategories")
> protected List<Category> childCategories = new ArrayList<Category>();
>
> ...
> }
>
> Thanks,
>
> -- markus.
>
> Greg Ederer wrote:
>> Hi,
>>
>> I have a Category class. According to my model, a Category can have
>> many parent Categorys and many child Categorys. I'm having trouble
>> getting the JPA annotations right for this relationship. I'm sure
>> that this must be trivially easy.
>>
>> The source might something look like:
>>
>> @Entity
>> public class Category
>> {
>> @Id
>> private Long id;
>>
>> protected String name;
>>
>> @???
>> protected List<Category> parentCategories = new ArrayList<Category>();
>>
>> @???
>> protected List<Category> childCategories = new ArrayList<Category>();
>>
>> ...
>> }
>>
>> What is the correct way to do this?
>>
>> Thanks!
>>
>> Greg
>>

-- 
| E R G O N O S I S
| Greg Ederer
| Lead Developer
| greg_at_ergonosis.com
| 360.774.6848
|