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Java > Open Source Codes > org > apache > ojb > broker > accesslayer > ReferencePrefetcher


1 package org.apache.ojb.broker.accesslayer;
2
3 /* Copyright 2002-2005 The Apache Software Foundation
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17
18 import java.util.ArrayList JavaDoc;
19 import java.util.Collection JavaDoc;
20 import java.util.HashMap JavaDoc;
21 import java.util.HashSet JavaDoc;
22 import java.util.Iterator JavaDoc;
23
24 import org.apache.ojb.broker.Identity;
25 import org.apache.ojb.broker.PersistenceBroker;
26 import org.apache.ojb.broker.cache.ObjectCache;
27 import org.apache.ojb.broker.core.PersistenceBrokerImpl;
28 import org.apache.ojb.broker.metadata.ClassDescriptor;
29 import org.apache.ojb.broker.metadata.ObjectReferenceDescriptor;
30 import org.apache.ojb.broker.metadata.fieldaccess.PersistentField;
31 import org.apache.ojb.broker.query.Query;
32
33 /**
34  * Relationship Prefetcher for References.
35  *
36  * @author <a HREF="mailto:jbraeuchi@hotmail.com">Jakob Braeuchi</a>
37  * @version $Id: ReferencePrefetcher.java,v 1.20.2.3 2005/12/21 22:22:58 tomdz Exp $
38  */
39 public class ReferencePrefetcher extends RelationshipPrefetcherImpl
40 {
41
42     /**
43     * Constructor for ReferencePrefetcher.
44     * @param aBroker
45     * @param anOrd
46     */
47     public ReferencePrefetcher(PersistenceBrokerImpl aBroker, ObjectReferenceDescriptor anOrd)
48     {
49         super(aBroker, anOrd);
50     }
51
52     /**
53      * Associate the batched Children with their owner object.
54      * Loop over owners
55      */
56     protected void associateBatched(Collection JavaDoc owners, Collection JavaDoc children)
57     {
58         ObjectReferenceDescriptor ord = getObjectReferenceDescriptor();
59         ClassDescriptor cld = getOwnerClassDescriptor();
60         Object JavaDoc owner;
61         Object JavaDoc relatedObject;
62         Object JavaDoc fkValues[];
63         Identity id;
64         PersistenceBroker pb = getBroker();
65         PersistentField field = ord.getPersistentField();
66         Class JavaDoc topLevelClass = pb.getTopLevelClass(ord.getItemClass());
67         HashMap JavaDoc childrenMap = new HashMap JavaDoc(children.size());
68
69
70         for (Iterator JavaDoc it = children.iterator(); it.hasNext(); )
71         {
72             relatedObject = it.next();
73             childrenMap.put(pb.serviceIdentity().buildIdentity(relatedObject), relatedObject);
74         }
75
76         for (Iterator JavaDoc it = owners.iterator(); it.hasNext(); )
77         {
78             owner = it.next();
79             fkValues = ord.getForeignKeyValues(owner,cld);
80             if (isNull(fkValues))
81             {
82                 field.set(owner, null);
83                 continue;
84             }
85             id = pb.serviceIdentity().buildIdentity(null, topLevelClass, fkValues);
86             relatedObject = childrenMap.get(id);
87             field.set(owner, relatedObject);
88         }
89     }
90
91     private boolean isNull(Object JavaDoc[] arr)
92     {
93         for (int i = 0; i < arr.length; i++)
94         {
95             if (arr[i] != null)
96             {
97                 return false;
98             }
99         }
100         return true;
101     }
102     
103     /**
104      * Build the multiple queries for one relationship because of limitation of IN(...)
105      * @param owners Collection containing all objects of the ONE side
106      * @param children Collection where related objects found in the cache should be added.
107      */
108     protected Query[] buildPrefetchQueries(Collection JavaDoc owners, Collection JavaDoc children)
109     {
110         ClassDescriptor cld = getOwnerClassDescriptor();
111         ObjectReferenceDescriptor ord = getObjectReferenceDescriptor();
112         Collection JavaDoc queries = new ArrayList JavaDoc(owners.size());
113         Collection JavaDoc idsSubset = new HashSet JavaDoc(owners.size());
114         Iterator JavaDoc iter = owners.iterator();
115         Class JavaDoc topLevelClass = getBroker().getTopLevelClass(ord.getItemClass());
116         Object JavaDoc[] fkValues;
117         Object JavaDoc owner;
118         Identity id;
119         PersistenceBroker pb = getBroker();
120         ObjectCache cache = pb.serviceObjectCache();
121
122         while (iter.hasNext())
123         {
124             owner = iter.next();
125             fkValues = ord.getForeignKeyValues(owner,cld);
126             if (isNull(fkValues))
127             {
128                 continue;
129             }
130             id = pb.serviceIdentity().buildIdentity(null, topLevelClass, fkValues);
131             if (cache.lookup(id) != null)
132             {
133                 children.add(pb.getObjectByIdentity(id));
134                 continue;
135             }
136             idsSubset.add(id);
137             if (idsSubset.size() == pkLimit)
138             {
139                 queries.add(buildPrefetchQuery(idsSubset));
140                 idsSubset.clear();
141             }
142         }
143
144         if (idsSubset.size() > 0)
145         {
146             queries.add(buildPrefetchQuery(idsSubset));
147         }
148
149         return (Query[]) queries.toArray(new Query[queries.size()]);
150     }
151
152     /**
153      * @see org.apache.ojb.broker.accesslayer.RelationshipPrefetcherImpl#buildPrefetchCriteria(java.util.Collection, org.apache.ojb.broker.metadata.FieldDescriptor[])
154      */
155     protected Query buildPrefetchQuery(Collection JavaDoc ids)
156     {
157         return buildPrefetchQuery(ids, getItemClassDescriptor().getPkFields());
158     }
159 }
160
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