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Java > Open Source Codes > org > objectstyle > cayenne > query > RelationshipQuery


1 /* ====================================================================
2  *
3  * The ObjectStyle Group Software License, version 1.1
4  * ObjectStyle Group - http://objectstyle.org/
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6  * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
7  * of the software. All rights reserved.
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10  * modification, are permitted provided that the following conditions
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22  * must include the following acknowlegement:
23  * "This product includes software developed by independent contributors
24  * and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
25  * Alternately, this acknowlegement may appear in the software itself,
26  * if and wherever such third-party acknowlegements normally appear.
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28  * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
29  * or promote products derived from this software without prior written
30  * permission. For written permission, email
31  * "andrus at objectstyle dot org".
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52  * individuals and hosted on ObjectStyle Group web site. For more
53  * information on the ObjectStyle Group, please see
54  * <http://objectstyle.org/>.
55  */
56 package org.objectstyle.cayenne.query;
57
58 import java.util.Collection JavaDoc;
59 import java.util.Collections JavaDoc;
60
61 import org.objectstyle.cayenne.CayenneRuntimeException;
62 import org.objectstyle.cayenne.DataObject;
63 import org.objectstyle.cayenne.exp.Expression;
64 import org.objectstyle.cayenne.exp.ExpressionFactory;
65 import org.objectstyle.cayenne.map.Entity;
66 import org.objectstyle.cayenne.map.ObjEntity;
67 import org.objectstyle.cayenne.map.ObjRelationship;
68
69 /**
70  * A query that selects objects related to a given object. It can be used for resolving
71  * to-many relationships. It is in fact used for this purpose internally in Cayenne.
72  *
73  * @since 1.2
74  * @author Andrus Adamchik
75  */
76 public class RelationshipQuery extends AbstractQuery implements GenericSelectQuery {
77
78     protected DataObject object;
79
80     // TODO: ObjRelationship is not serializable ... need to serialize its name instead
81 protected ObjRelationship relationship;
82
83     /**
84      * Creates a new Relationship query based for a DataObject and relationship name. This
85      * constructor will only work if a DataObject has a non-null DataContext.
86      */
87     public RelationshipQuery(DataObject object, String JavaDoc relationshipName) {
88         Entity entity = object.getDataContext().getEntityResolver().lookupObjEntity(
89                 object);
90
91         ObjRelationship relationship = (ObjRelationship) entity
92                 .getRelationship(relationshipName);
93
94         if (relationship == null) {
95             throw new CayenneRuntimeException("No relationship named "
96                     + relationshipName
97                     + " found in entity "
98                     + entity);
99         }
100
101         super.setRoot(relationship.getTargetEntity());
102
103         this.object = object;
104         this.relationship = relationship;
105     }
106
107     public RelationshipQuery(DataObject object, ObjRelationship relationship) {
108
109         super.setRoot(relationship.getTargetEntity());
110
111         this.object = object;
112         this.relationship = relationship;
113     }
114
115     public ObjRelationship getRelationship() {
116         return relationship;
117     }
118
119     public DataObject getObject() {
120         return object;
121     }
122
123     public String JavaDoc getCachePolicy() {
124         return GenericSelectQuery.NO_CACHE;
125     }
126
127     public boolean isFetchingDataRows() {
128         return false;
129     }
130
131     public boolean isRefreshingObjects() {
132         return true;
133     }
134
135     public boolean isResolvingInherited() {
136         return true;
137     }
138
139     public int getPageSize() {
140         return 0;
141     }
142
143     public int getFetchLimit() {
144         return 0;
145     }
146
147     public Collection JavaDoc getJointPrefetches() {
148         return Collections.EMPTY_SET;
149     }
150
151     /**
152      * Creates a SelectQuery for relationship, delegating SQLAction creation to this newly
153      * created query.
154      */
155     public SQLAction createSQLAction(SQLActionVisitor visitor) {
156
157         // build a SelectQuery that Cayenne knows how to process.
158
159         ObjEntity targetEntity = (ObjEntity) relationship.getTargetEntity();
160         Expression qualifier = ExpressionFactory.matchDbExp(relationship
161                 .getReverseDbRelationshipPath(), object);
162
163         SelectQuery select = new SelectQuery(targetEntity, qualifier);
164
165         // set runtime properrties
166 select.setRefreshingObjects(isRefreshingObjects());
167         select.setResolvingInherited(isResolvingInherited());
168         select.setPageSize(getPageSize());
169         select.setFetchLimit(getFetchLimit());
170         select.setFetchingDataRows(isFetchingDataRows());
171
172         // delegate to select query
173 return select.createSQLAction(visitor);
174     }
175 }
176
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