Question

I have a tree-like object, managed by Hibernate. The object has a list of children and each child has its own custom_order within a parent:

<hibernate-mapping>
  <class name="MyClass" .../>
  <property .../>
  <property .../>
  <list name="children" cascade="save-update" inverse="false">
    <key column="parent_id"/>
    <index column="custom_order"/>
    <one-to-many class="MyClass"/>
  </list>
</hibernate-mapping>

The custom_order exists here in order to maintain the order of children within a parent but has no representation in the Java POJO and is managed directly by Hibernate. The only thing I have to do is to supply a list and custom_order will be auto-generated. So far so good.

What I want to achieve is the ability to use Criteria API and order by custom_order. At the moment I simply can not do anything like

criteria.addOrder(Order.asc("custom_order"));

because there is no such POJO property.

Question: is there a way to use Criteria API for this scenario without adding POJO getter/setter?

EDIT: I don’t mind adding relevant custom_order attribute to MyClass but I just don’t think this is possible in Hibernate.

Answer 1

It is possible to map custom_order attribute to MyClass without adding getter or setter for this attribute . Just configure custom_order attribute to be access by field .

Also , to prevent developers from changing the custom_order property using reflection , make custom_order to be read-only by setting insert and update to false:

<property name="customerOrder" column="custom_order" access="field" insert="false" update="false"/>

Currently , Order in Criteria API only can process mapped properties . If you don’t want to map custom_order attribute to MyClass, you can achieve your purpose if Order in Criteria API support sorting by native SQL. There are some requests for this support (HHH-1356 ,HHH-2381 , HHH-3315) but they are still unresolved now.

Luckily , someone had already extended the Order class in order to support ordering by native SQL . So ,if you don’t map custom_order column for MyClass , you can simply use this extended Order class :

addOrder(new NativeSQLOrder("custom_order" ,true))