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.lang.reflect.Array;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.HashMap;

 import java.util.HashSet;

 import java.util.Iterator;

 import java.util.List;

 import org.apache.ojb.broker.Identity;

 import org.apache.ojb.broker.ManageableCollection;

 import org.apache.ojb.broker.OJBRuntimeException;

 import org.apache.ojb.broker.PersistenceBroker;

 import org.apache.ojb.broker.IdentityFactory;

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

 import org.apache.ojb.broker.core.proxy.CollectionProxyDefaultImpl;

 import org.apache.ojb.broker.core.proxy.ProxyHelper;

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

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

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

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

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

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

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

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

 import org.apache.ojb.broker.util.BrokerHelper;

 import org.apache.ojb.broker.util.collections.RemovalAwareCollection;

 import org.apache.ojb.broker.util.collections.RemovalAwareList;

 import org.apache.ojb.broker.util.collections.RemovalAwareSet;

 /**

  * Relationship Prefetcher for Collections.

  *

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

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

  */

 public class CollectionPrefetcher extends RelationshipPrefetcherImpl

 {

     /**

      * Constructor for CollectionPrefetcher.

      *

      * @param aBroker

      * @param anOrd

      */

     public CollectionPrefetcher(PersistenceBrokerImpl aBroker, ObjectReferenceDescriptor anOrd)

     {

         super(aBroker, anOrd);

     }

     /**

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

      *

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

      */

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

     {

         ClassDescriptor cld = getOwnerClassDescriptor();

         Class topLevelClass = getBroker().getTopLevelClass(cld.getClassOfObject());

         BrokerHelper helper = getBroker().serviceBrokerHelper();

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

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

         Object[] fkValues;

         Object owner;

         Identity id;

         Iterator iter = owners.iterator();

         while (iter.hasNext())

         {

             owner = iter.next();

             fkValues = helper.extractValueArray(helper.getKeyValues(cld, owner));

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

             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()]);

     }

     /**

      * Build the query to perform a batched read get orderBy settings from CollectionDescriptor

      *

      * @param ids Collection containing all identities of objects of the ONE side

      */

     protected Query buildPrefetchQuery(Collection ids)

     {

         CollectionDescriptor cds = getCollectionDescriptor();

         QueryByCriteria query = buildPrefetchQuery(ids, cds.getForeignKeyFieldDescriptors(getItemClassDescriptor()));

         // check if collection must be ordered

         if (!cds.getOrderBy().isEmpty())

         {

             Iterator iter = cds.getOrderBy().iterator();

             while (iter.hasNext())

             {

                 query.addOrderBy((FieldHelper) iter.next());

             }

         }

         return query;

     }

     /**

      * associate the batched Children with their owner object loop over children

      */

     protected void associateBatched(Collection owners, Collection children)

     {

         CollectionDescriptor cds = getCollectionDescriptor();

         PersistentField field = cds.getPersistentField();

         PersistenceBroker pb = getBroker();

         Class ownerTopLevelClass = pb.getTopLevelClass(getOwnerClassDescriptor().getClassOfObject());

         Class collectionClass = cds.getCollectionClass(); // this collection type will be used:

         HashMap ownerIdsToLists = new HashMap(owners.size());

         IdentityFactory identityFactory = pb.serviceIdentity();

         // initialize the owner list map

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

         {

             Object owner = it.next();

             ownerIdsToLists.put(identityFactory.buildIdentity(getOwnerClassDescriptor(), owner), new ArrayList());

         }

         // build the children lists for the owners

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

         {

             Object child = it.next();

             // BRJ: use cld for real class, relatedObject could be Proxy

             ClassDescriptor cld = getDescriptorRepository().getDescriptorFor(ProxyHelper.getRealClass(child));

             Object[] fkValues = cds.getForeignKeyValues(child, cld);

             Identity ownerId = identityFactory.buildIdentity(null, ownerTopLevelClass, fkValues);

             List list = (List) ownerIdsToLists.get(ownerId);

             if (list != null)

             {

                 list.add(child);

             }

         }

         // connect children list to owners

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

         {

             Object result;

             Object owner = it.next();

             Identity ownerId = identityFactory.buildIdentity(owner);

             List list = (List) ownerIdsToLists.get(ownerId);

             if ((collectionClass == null) && field.getType().isArray())

             {

                 int length = list.size();

                 Class itemtype = field.getType().getComponentType();

                 result = Array.newInstance(itemtype, length);

                 for (int j = 0; j < length; j++)

                 {

                     Array.set(result, j, list.get(j));

                 }

             }

             else

             {

                 ManageableCollection col = createCollection(cds, collectionClass);

                 for (Iterator it2 = list.iterator(); it2.hasNext();)

                 {

                     col.ojbAdd(it2.next());

                 }

                 result = col;

             }

             Object value = field.get(owner);

             if ((value instanceof CollectionProxyDefaultImpl) && (result instanceof Collection))

             {

                 ((CollectionProxyDefaultImpl) value).setData((Collection) result);

             }

             else

             {

                 field.set(owner, result);

             }

         }

     }

     /**

      * Create a collection object of the given collection type. If none has been given,

      * OJB uses RemovalAwareList, RemovalAwareSet, or RemovalAwareCollection depending

      * on the field type. 

      * 

      * @param desc            The collection descriptor

      * @param collectionClass The collection class specified in the collection-descriptor

      * @return The collection object

      */

     protected ManageableCollection createCollection(CollectionDescriptor desc, Class collectionClass)

     {

         Class                fieldType = desc.getPersistentField().getType();

         ManageableCollection col;

         if (collectionClass == null)

         {

             if (ManageableCollection.class.isAssignableFrom(fieldType))

             {

                 try

                 {

                     col = (ManageableCollection)fieldType.newInstance();

                 }

                 catch (Exception e)

                 {

                     throw new OJBRuntimeException("Cannot instantiate the default collection type "+fieldType.getName()+" of collection "+desc.getAttributeName()+" in type "+desc.getClassDescriptor().getClassNameOfObject());

                 }

             }

             else if (fieldType.isAssignableFrom(RemovalAwareCollection.class))

             {

                 col = new RemovalAwareCollection();

             }

             else if (fieldType.isAssignableFrom(RemovalAwareList.class))

             {

                 col = new RemovalAwareList();

             }

             else if (fieldType.isAssignableFrom(RemovalAwareSet.class))

             {

                 col = new RemovalAwareSet();

             }

             else

             {

                 throw new MetadataException("Cannot determine a default collection type for collection "+desc.getAttributeName()+" in type "+desc.getClassDescriptor().getClassNameOfObject());

             }

         }

         else

         {

             try

             {

                 col = (ManageableCollection)collectionClass.newInstance();

             }

             catch (Exception e)

             {

                 throw new OJBRuntimeException("Cannot instantiate the collection class "+collectionClass.getName()+" of collection "+desc.getAttributeName()+" in type "+desc.getClassDescriptor().getClassNameOfObject());

             }

         }

         return col;

     }

     protected CollectionDescriptor getCollectionDescriptor()

     {

         return (CollectionDescriptor) getObjectReferenceDescriptor();

     }

 }