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());
     }
 }