Hibernate - automatically assign foreign key to child?

Question

Ok, so I have 2 objects, Parent and Child. The child basically looks like this:

public class Child implements Serializable 
{

    // primary (composite) key
    private int parentId;
    private String name;

    // random value
    private String val;

    public Child(String name, String val) {
        this.name = name;
        this.val = val;
        // note: parentId is not assigned a value
    }

    public void setParentId(int id) {

    [...]
}

What I want is basically for hibernate to automatically set the parent id of the Child once a Parent object is created. Is this possible or do I have to add child objects to the parent object after the parent object has been saved to the database?

The xml mapping of the parent looks as such:

`<map name="children" inverse="true" lazy="true" cascade="all,delete-orphan">
    <cache usage="nonstrict-read-write"/>
    <key column="parent_id"/>
    <index column="child_name" type="string"/>
    <one-to-many class="myPack.Child"/>
</map>`

and the xml of the child:

<hibernate-mapping package="myPack">

    <class name="Child" table="child_tbl" lazy="true">

        <composite-id>
            <key-property name="ParentId" type="int" column="parent_id"/>
            <key-property name="Name" column="name" type="string"/>
        </composite-id>

        <property name="Val" blablabla
[...]

Answer 1

When you want hibernate to insert parent-child together with a foreign key use object mapping rather than ids.

Lets take an example from here,

public class AMain {
 
 //Properties of A.
 List<ASub3> subList;
.....
}

public class ASub3 {
 .....  
 AMain parent;
 .....
}

in the hbm.xml file in AMain add,

    <list name="subList" inverse="true" cascade="all" lazy="false">
         <key column="a_id" />
         <list-index column="as3_id" />
         <one-to-many class="com.manu.hibernate.mappings.domain.ASub3" />
    </list>

in Asub3 add,

<many-to-one name="parent" class="com.manu.hibernate.mappings.domain.AMain" 
column="a_id" unique="true" cascade="save-update" />

Now, in the client code use the beans as below,

     AMain a = new AMain("A");
     ASub3 as3a = new ASub3("List - 1");
     ASub3 as3b = new ASub3("List - 2");
     ASub3 as3c = new ASub3("List - 3");
     as3a.setParent(a);
     as3b.setParent(a);
     as3c.setParent(a);
     List<ASub3> subList = new ArrayList<ASub3>();
     subList.add(as3a);
     subList.add(as3b);
     subList.add(as3c);

     a.setSubList(subList);

Now, if youn save AMain both AMain and ASub3 will be updated(I mean corresponding table) with a foreign key to AMain.