package org.apache.ojb.broker.accesslayer;

 /* Copyright 2002-2005 The Apache Software Foundation

  *

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  *

  *     http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.HashMap;

 import java.util.HashSet;

 import java.util.Iterator;

 import org.apache.ojb.broker.Identity;

 import org.apache.ojb.broker.PersistenceBroker;

 import org.apache.ojb.broker.cache.ObjectCache;

 import org.apache.ojb.broker.core.PersistenceBrokerImpl;

 import org.apache.ojb.broker.metadata.ClassDescriptor;

 import org.apache.ojb.broker.metadata.ObjectReferenceDescriptor;

 import org.apache.ojb.broker.metadata.fieldaccess.PersistentField;

 import org.apache.ojb.broker.query.Query;

 /**

  * Relationship Prefetcher for References.

  *

  * @author <a href="mailto:jbraeuchi@hotmail.com">Jakob Braeuchi</a>

  * @version $Id: ReferencePrefetcher.java,v 1.1 2007-08-24 22:17:30 ewestfal Exp $

  */

 public class ReferencePrefetcher extends RelationshipPrefetcherImpl

 {

     /**

     * Constructor for ReferencePrefetcher.

     * @param aBroker

     * @param anOrd

     */

     public ReferencePrefetcher(PersistenceBrokerImpl aBroker, ObjectReferenceDescriptor anOrd)

     {

         super(aBroker, anOrd);

     }

     /**

      * Associate the batched Children with their owner object.

      * Loop over owners

      */

     protected void associateBatched(Collection owners, Collection children)

     {

         ObjectReferenceDescriptor ord = getObjectReferenceDescriptor();

         ClassDescriptor cld = getOwnerClassDescriptor();

         Object owner;

         Object relatedObject;

         Object fkValues[];

         Identity id;

         PersistenceBroker pb = getBroker();

         PersistentField field = ord.getPersistentField();

         Class topLevelClass = pb.getTopLevelClass(ord.getItemClass());

         HashMap childrenMap = new HashMap(children.size());

         for (Iterator it = children.iterator(); it.hasNext(); )

         {

             relatedObject = it.next();

             childrenMap.put(pb.serviceIdentity().buildIdentity(relatedObject), relatedObject);

         }

         for (Iterator it = owners.iterator(); it.hasNext(); )

         {

             owner = it.next();

             fkValues = ord.getForeignKeyValues(owner,cld);

             if (isNull(fkValues))

             {

                 field.set(owner, null);

                 continue;

             }

             id = pb.serviceIdentity().buildIdentity(null, topLevelClass, fkValues);

             relatedObject = childrenMap.get(id);

             field.set(owner, relatedObject);

         }

     }

     private boolean isNull(Object[] arr)

     {

         for (int i = 0; i < arr.length; i++)

         {

             if (arr[i] != null)

             {

                 return false;

             }

         }

         return true;

     }

     /**

      * Build the multiple queries for one relationship because of limitation of IN(...)

      * @param owners Collection containing all objects of the ONE side

      * @param children Collection where related objects found in the cache should be added.

      */

     protected Query[] buildPrefetchQueries(Collection owners, Collection children)

     {

         ClassDescriptor cld = getOwnerClassDescriptor();

         ObjectReferenceDescriptor ord = getObjectReferenceDescriptor();

         Collection queries = new ArrayList(owners.size());

         Collection idsSubset = new HashSet(owners.size());

         Iterator iter = owners.iterator();

         Class topLevelClass = getBroker().getTopLevelClass(ord.getItemClass());

         Object[] fkValues;

         Object owner;

         Identity id;

         PersistenceBroker pb = getBroker();

         ObjectCache cache = pb.serviceObjectCache();

         while (iter.hasNext())

         {

             owner = iter.next();

             fkValues = ord.getForeignKeyValues(owner,cld);

             if (isNull(fkValues))

             {

                 continue;

             }

             id = pb.serviceIdentity().buildIdentity(null, topLevelClass, fkValues);

             if (cache.lookup(id) != null)

             {

                 children.add(pb.getObjectByIdentity(id));

                 continue;

             }

             idsSubset.add(id);

             if (idsSubset.size() == pkLimit)

             {

                 queries.add(buildPrefetchQuery(idsSubset));

                 idsSubset.clear();

             }

         }

         if (idsSubset.size() > 0)

         {

             queries.add(buildPrefetchQuery(idsSubset));

         }

         return (Query[]) queries.toArray(new Query[queries.size()]);

     }

     /**

      * @see org.apache.ojb.broker.accesslayer.RelationshipPrefetcherImpl#buildPrefetchCriteria(java.util.Collection, org.apache.ojb.broker.metadata.FieldDescriptor[])

      */

     protected Query buildPrefetchQuery(Collection ids)

     {

         return buildPrefetchQuery(ids, getItemClassDescriptor().getPkFields());

     }

 }