eager fetching lazy collection with criteria?

tdennison · **Joined:** Wed Nov 05, 2008 1:17 pm **Posts:** 7

I need to eager fetch a lazy collection with Criteria. The JPA book seems to indicate that I can use FetchMode.JOIN to override laziness on a collection and force it to load. This doesn't seem to be working for my example below:

Mapping file

Code:

<hibernate-mapping auto-import="true" default-lazy="true" package="com.orders" >

    <class name="Customer" table="customers">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="name"/>
        <set name="phones" table="customer_phone" cascade="all" lazy="true"">
           <key column="customer_id" />
           <many-to-many column="phone_id" class="Phone" />
        </set>
    </class>

    <class name="Phone" table="phones">
       <id name="id">
          <generator class="native" />
       </id>
       <property name="number" />
       <property name="type" />
       
      <set name="customers" inverse="true" table="customer_phone">
             <key column="phone_id"/>
             <many-to-many column="customer_id"
                         class="Customer"/>
      </set>    
   </class>
    
</hibernate-mapping>

Unit test

Code:

   public void testFetchPhonesEager() throws Exception
   {
      Session session = sessionFactory.openSession();
      Criteria criteria = session.createCriteria( Customer.class, "customer" )
      .add( Restrictions.idEq( 1l ) )
      .createAlias( "phones", "p")
      .setFetchMode( "p", FetchMode.JOIN );
      
      List<Customer> customers = criteria.list();
      Set<Customer> customerSet = new HashSet<Customer>(customers);
      // uncomment these two lines and everything works fine
//      for (Customer customer : customers)
//         Hibernate.initialize( customer.getPhones() ); 
      session.close();

      final Customer customer = customers.get( 0 );
      // Problem: LazyInitializationException is thrown!!!
      assertTrue(customer.getPhones().size() == 3);
   }

mmerder · **Posted:** Thu Feb 05, 2009 8:53 am

Change your criteria to:

Code:

session.createCriteria( Customer.class, "customer" )
      .add( Restrictions.idEq( 1l ) )
      .setFetchMode( "phones", FetchMode.JOIN ); 

tdennison · **Joined:** Wed Nov 05, 2008 1:17 pm **Posts:** 7

Thanks! That does work. So....looks like using createAlias() without the
jointype parameter will default to an inner join.

Can I do this without using an outer join? Is there a way to use a select or sub select to fetch the phones collection eagerly?

SIau_Tie · **Posted:** Thu Feb 05, 2009 9:46 am

tdennison wrote:

Thanks! That does work. So....looks like using createAlias() without the
jointype parameter will default to an inner join.

Can I do this without using an outer join? Is there a way to use a select or sub select to fetch the phones collection eagerly?

Code:

session.createCriteria( Customer.class, "customer" )
      .add( Restrictions.idEq( 1l ) );
...
Hibernate.initialize(customer.getPhones());

otherway, you can set fetch mode to subselect in your hbm.xml

Code:

<set name="phones" fetch="subselect"...>
</set>

tdennison · **Joined:** Wed Nov 05, 2008 1:17 pm **Posts:** 7

I can get the Hibernate.initialize() to work properly.

However, I using the fetch="subselect" doesn't seem to work. Is there
some way to use fetch="subselect" in an eager manner with criteria? I
tried FetchMode.DEFAULT (which is supposed to use the mapped fetch
method) to no avail.

mmerder · **Posted:** Thu Feb 05, 2009 11:15 am

No, I think its not possible, you can only enable it using join.