Example of unidiretional many-to-many with composite keys

kshenes · **Joined:** Wed Feb 07, 2007 6:05 pm **Posts:** 10

Can anyone point me to an example using a unidirectional many-to-many relationship with both entities have composite primary keys.

Entity A has a primary key that looks like this

int id
String name
String myName

Entity B has a primary key that looks like this

int id
String name
String anotherName

I want to define the many-to-many in A's mapping file.

every possible combination I have attempted always generates the mapping exception

A must have same number of columns as the referenced primary key B

any help would be greatly appreciated.

(I have read through the java persistence with hibernate, but they always use simple keys).

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

Assuming that id and name are in the join table (hopefully you can figure out any other permutations from this example):

Code:

<class name="B" ...>
  <composite-id>
    <key-property name="id" type="integer"/>
    <key-property name="name" type="string"/>
    <key-property name="anotherName" type="string"/>
  </composite-id>
  <properties name="joinRefB">
    <property name="id" insert="false" update="false"/>
    <property name="name" insert="false" update="false"/>
  </properties>
  ...
</class>

Code:

<class name="A" ...>
  <composite-id>
    <key-property name="id" type="integer"/>
    <key-property name="name" type="string"/>
    <key-property name="myName" type="string"/>
  </composite-id>
  ...
  <set name="Bs" table="AtoBlink" ...>
    <key>
      <formula>id</formula>
      <formula>name</formula>
    </key>
    <many-to-many class="A" property-ref="joinRefB"/>
  </set>
</class>

I think.

Maybe :)

kshenes · **Joined:** Wed Feb 07, 2007 6:05 pm **Posts:** 10

Thanks for the input.

The XML for class A

Code:

    <key>
      <formula>id</formula>
      <formula>name</formula>
    </key> 

is generating this error

The content of element type "key" must match "column"

Should the formula tags be column tags?

kshenes · **Joined:** Wed Feb 07, 2007 6:05 pm **Posts:** 10

Ok, this is what I ended up with and it works fine.

This is real entity that represents B

Code:

<hibernate-mapping default-lazy="false">
   <class name="CifsShare" table="CifsShare">
      <composite-id name="key" class="CifsSharePk">
         <key-property name="dataStoreId" />
         <key-property name="primaryIpAddr"/>
         <key-property name="shareName"/>
      </composite-id>

       <property name="fileSystem"/> 
       <property name="relativePath"/>
       <property name="description"/>

        <properties name="joinRefCifsServer">
           <property name="shareName" insert="false" update="false"/>
        </properties>
    </class>
</hibernate-mapping>

This is real entity that represents A

Code:

<hibernate-mapping default-lazy="false" >
   <class name="CifsFileServer" table="CifsFileServer">
      <composite-id name="key" class="CifsFileServerPk">
          <key-property name="dataStoreId" />
          <key-property name="primaryIpAddr"/>
          <key-property name="cifsIpAddr"/>
      </composite-id>

      <property name="adJoinDomain"/>
      <property name="adNetbiosName"/> 
      <property name="netbiosName"/>

      <set name="cifsShares" table="CifsServerShares" cascade="save-update">
         <key>
            <column name="dataStoreId"/>
            <column name="primaryIpAddr"/>
            <column name="cifsIpAddr"/>
          </key>
          <many-to-many class="CifsShare" property-ref="joinRefCifsServer"/>
      </set>
   </class>
</hibernate-mapping>

Thanks for your help!