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


1 /* ====================================================================
2  *
3  * The ObjectStyle Group Software License, version 1.1
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56 package org.objectstyle.cayenne.query;
57
58 import java.util.Iterator JavaDoc;
59
60 import org.objectstyle.cayenne.CayenneRuntimeException;
61 import org.objectstyle.cayenne.exp.Expression;
62 import org.objectstyle.cayenne.map.EntityInheritanceTree;
63 import org.objectstyle.cayenne.map.EntityResolver;
64 import org.objectstyle.cayenne.map.ObjEntity;
65 import org.objectstyle.cayenne.map.ObjRelationship;
66
67 /**
68  * A SelectQuery to perform a prefetch based on another query. Used internally
69  * by Cayenne and is normally never used directly.
70  *
71  * @author Craig Miskell, Andrei Adamchik
72  */
73 public class PrefetchSelectQuery extends SelectQuery {
74     protected SelectQuery parentQuery;
75
76     /**
77      * The relationship path from root objects to the objects being prefetched.
78      */
79     protected String JavaDoc prefetchPath;
80
81     /**
82      * Stores the last ObjRelationship in the prefetch path.
83      */
84     protected ObjRelationship lastPrefetchHint;
85
86     /**
87      * Creates a prefetch query based on parent query.
88      *
89      * @since 1.1
90      */
91     public PrefetchSelectQuery(
92         EntityResolver resolver,
93         SelectQuery parentQuery,
94         String JavaDoc prefetch) {
95
96         setParentQuery(parentQuery);
97         setPrefetchPath(prefetch);
98
99         ObjEntity entity = resolver.lookupObjEntity(parentQuery);
100         EntityInheritanceTree inheritanceTree = resolver.lookupInheritanceTree(entity);
101         
102         Iterator JavaDoc it = entity.resolvePathComponents(prefetch);
103
104         // find root entity
105
106         ObjRelationship r = null;
107         while (it.hasNext()) {
108             r = (ObjRelationship) it.next();
109         }
110
111         if (r == null) {
112             throw new CayenneRuntimeException(
113                 "Invalid prefetch '" + prefetch + "' for entity: " + entity.getName());
114         }
115
116         setRoot(r.getTargetEntity());
117
118         // chain query and entity qualifiers
119 Expression queryQualifier = parentQuery.getQualifier();
120
121         Expression entityQualifier =
122             (inheritanceTree != null)
123                 ? inheritanceTree.qualifierForEntityAndSubclasses()
124                 : entity.getDeclaredQualifier();
125
126         if (entityQualifier != null) {
127             queryQualifier =
128                 (queryQualifier != null)
129                     ? queryQualifier.andExp(entityQualifier)
130                     : entityQualifier;
131         }
132
133         setQualifier(entity.translateToRelatedEntity(queryQualifier, prefetchPath));
134
135         if (r.isToMany() && !r.isFlattened()) {
136             setLastPrefetchHint(r);
137         }
138     }
139
140  
141     /**
142      * Returns the prefetchPath.
143      * @return String
144      */
145     public String JavaDoc getPrefetchPath() {
146         return prefetchPath;
147     }
148
149     /**
150      * Sets the prefetchPath.
151      * @param prefetchPath The prefetchPath to set
152      */
153     public void setPrefetchPath(String JavaDoc prefetchPath) {
154         this.prefetchPath = prefetchPath;
155     }
156
157     /**
158      * @since 1.1
159      */
160     public SelectQuery getParentQuery() {
161         return parentQuery;
162     }
163
164     /**
165      * @since 1.1
166      */
167     public void setParentQuery(SelectQuery parentQuery) {
168         this.parentQuery = parentQuery;
169     }
170
171     /**
172      * @since 1.1
173      */
174     public ObjRelationship getLastPrefetchHint() {
175         return lastPrefetchHint;
176     }
177
178     /**
179      * @since 1.1
180      */
181     public void setLastPrefetchHint(ObjRelationship relationship) {
182         lastPrefetchHint = relationship;
183     }
184 }
185
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