<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tim" default-access="field" >
   <class name="Parent"
      table="PARENT"
       >
      <id name="id" type="java.lang.Long">
         <column name="PARENT_ID" precision="10" scale="0" />
         <generator class="native">
         </generator>
      </id>

        <property name="name" type="java.lang.String">
           <column name="NAME" length="255" not-null="true" />
        </property>
      
      <set name="children"
           cascade="all,delete-orphan">

           <key column="PARENT_ID" />
           <one-to-many class="Child" />
      </set>
   </class>
   
   <class name="Child"
          table="CHILD">
          
      <id name="id" type="java.lang.Long">
         <column name="CHILD_ID" precision="10" scale="0" />
         <generator class="native">
         </generator>
      </id>

        <property name="name" type="string">
           <column name="CHILD_NAME" length="255" not-null="true" />
        </property>
       
   </class>
</hibernate-mapping>

Test case:
  public void onSetUp() throws Exception
   {
      // clean the data
      jdbcTemplate.execute( "delete from CHILD" );
      jdbcTemplate.execute( "delete from PARENT" );

      // stage the data
      jdbcTemplate
                  .execute( "insert into PARENT (PARENT_ID,NAME) values "
                            + "(500,'parent1')" );
      jdbcTemplate
                  .execute( "insert into PARENT (PARENT_ID,NAME) values "
                            + "(510,'parent2')" );

      jdbcTemplate.execute( "insert into CHILD (CHILD_ID, PARENT_ID, CHILD_NAME) values "
                            + "(300,500,'child1')" );
      jdbcTemplate.execute( "insert into CHILD (CHILD_ID, PARENT_ID, CHILD_NAME) values "
                            + "(310,500,'child2')" );
      jdbcTemplate.execute( "insert into CHILD (CHILD_ID, PARENT_ID, CHILD_NAME) values "
                            + "(320,510,'child3')" );
       
      setComplete();
      startNewTransaction();
   }
   @NotTransactional
   public void testRemoveChildFromDetached() throws Exception
   {
      final Parent parent = new Parent(  );
      parent.setId( Long.valueOf( "500" ) );
      parent.setName( "parent1_modified" );
     
      final Child child1 = new Child();
      child1.setName( "child1_modified" );
      child1.setId( Long.valueOf( "310") );
      final Set<Child> children = new LinkedHashSet<Child>();
      children.add( child1 );
      parent.setChildren( children );
     
      System.out.println( "******* saveOrUpdate() of parent: " + parent + " *******" );
      // NOTE: uncomment the following for the test to pass
//      hibernateTemplate.merge( parent );
      // NOTE: this line will not result in the child deletion
      hibernateTemplate.saveOrUpdate( parent );
   
      endTransaction();
      startNewTransaction();
      System.out.println( "******* loading parent again *********" );
      final Parent parentCheck = (Parent)hibernateTemplate.get( Parent.class, Long.valueOf( 500 ) );
      assertTrue( parentCheck.getChildren().size() == 1);

      final long rowCount =
         jdbcTemplate.queryForLong( "select count(*) from CHILD where CHILD_ID='300'" );
      assertEquals( "Count of rows in CHILD should be 0 for CHILD_ID='300'", 0, rowCount );
   }