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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
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package org.apache.cayenne.query;
import java.util.Iterator;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.exp.Expression;
import org.apache.cayenne.map.EntityResolver;
import org.apache.cayenne.map.ObjRelationship;
import org.apache.cayenne.reflect.ClassDescriptor;
import org.apache.cayenne.util.CayenneMapEntry;
/**
* Preprocessor and router of SelectQuery prefetches.
*
* @since 1.2
*/
class SelectQueryPrefetchRouterAction implements PrefetchProcessor {
SelectQuery query;
QueryRouter router;
EntityResolver resolver;
ClassDescriptor classDescriptor;
/**
* Routes query prefetches, but not the query itself.
*/
void route(SelectQuery query, QueryRouter router, EntityResolver resolver) {
if (!query.isFetchingDataRows() && query.getPrefetchTree() != null) {
this.query = query;
this.router = router;
this.resolver = resolver;
this.classDescriptor = query.getMetaData(resolver).getClassDescriptor();
query.getPrefetchTree().traverse(this);
}
}
public boolean startPhantomPrefetch(PrefetchTreeNode node) {
return true;
}
public boolean startDisjointPrefetch(PrefetchTreeNode node) {
// don't do anything to root
if (node == query.getPrefetchTree()) {
return true;
}
String prefetchPath = node.getPath();
// find last relationship
Iterator<CayenneMapEntry> it = classDescriptor.getEntity().resolvePathComponents(
prefetchPath);
ObjRelationship relationship = null;
while (it.hasNext()) {
relationship = (ObjRelationship) it.next();
}
if (relationship == null) {
throw new CayenneRuntimeException(
"Invalid prefetch '%s' for entity '%s'",
prefetchPath,
classDescriptor.getEntity().getName());
}
// chain query and entity qualifiers
Expression queryQualifier = query.getQualifier();
Expression entityQualifier = classDescriptor
.getEntityInheritanceTree()
.qualifierForEntityAndSubclasses();
if (entityQualifier != null) {
queryQualifier = (queryQualifier != null) ? queryQualifier
.andExp(entityQualifier) : entityQualifier;
}
// create and configure PrefetchSelectQuery
PrefetchSelectQuery prefetchQuery = new PrefetchSelectQuery(
query,
prefetchPath,
relationship);
prefetchQuery.setQualifier(classDescriptor.getEntity().translateToRelatedEntity(
queryQualifier,
prefetchPath));
if (relationship.isSourceIndependentFromTargetChange()) {
// setup extra result columns to be able to relate result rows to the parent
// result objects.
prefetchQuery.addResultPath("db:"
+ relationship.getReverseDbRelationshipPath());
}
// pass prefetch subtree to enable joint prefetches...
prefetchQuery.setPrefetchTree(node);
// route...
prefetchQuery.route(router, resolver, null);
return true;
}
public boolean startJointPrefetch(PrefetchTreeNode node) {
// simply pass through
return true;
}
public boolean startUnknownPrefetch(PrefetchTreeNode node) {
// don't do anything to root
if (node == query.getPrefetchTree()) {
return true;
}
// route unknown as disjoint...
return startDisjointPrefetch(node);
}
public void finishPrefetch(PrefetchTreeNode node) {
}
}