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* to you under the Apache License, Version 2.0 (the
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package org.apache.cayenne.query;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.exp.Expression;
import org.apache.cayenne.map.EntityInheritanceTree;
import org.apache.cayenne.map.EntityResolver;
import org.apache.cayenne.map.ObjEntity;
import org.apache.cayenne.map.ObjRelationship;
import org.apache.cayenne.util.Util;
/**
* A SelectQuery to perform a prefetch based on another query. Used internally by Cayenne
* and is normally never used directly.
*
* @author Craig Miskell, Andrei Adamchik
*/
public class PrefetchSelectQuery extends SelectQuery {
protected SelectQuery parentQuery;
/**
* The relationship path from root objects to the objects being prefetched.
*/
protected String prefetchPath;
/**
* Stores the last ObjRelationship in the prefetch path.
*/
protected ObjRelationship lastPrefetchHint;
// TODO, Andrus 11/17/2005 - i guess we should deprecate
// SelectQuery.customDbAttribute, replacing it with "resultPaths" mechanism.
protected Collection resultPaths;
/**
* Creates a prefetch query based on parent query.
*
* @since 1.1
* @deprecated since 1.2 - passing EntityResolver in constructor is no longer needed,
* as prefetch query configuration alogrithm is moved out of this class.
* In fact this constructor will not correctly configure query to handle
* flattened prefetches.
*/
public PrefetchSelectQuery(EntityResolver resolver, SelectQuery parentQuery,
String prefetch) {
setParentQuery(parentQuery);
setPrefetchPath(prefetch);
ObjEntity entity = parentQuery.getMetaData(resolver).getObjEntity();
EntityInheritanceTree inheritanceTree = resolver.lookupInheritanceTree(entity);
Iterator it = entity.resolvePathComponents(prefetch);
// find root entity
ObjRelationship r = null;
while (it.hasNext()) {
r = (ObjRelationship) it.next();
}
if (r == null) {
throw new CayenneRuntimeException("Invalid prefetch '"
+ prefetch
+ "' for entity: "
+ entity.getName());
}
setRoot(r.getTargetEntity());
// chain query and entity qualifiers
Expression queryQualifier = parentQuery.getQualifier();
Expression entityQualifier = (inheritanceTree != null) ? inheritanceTree
.qualifierForEntityAndSubclasses() : entity.getDeclaredQualifier();
if (entityQualifier != null) {
queryQualifier = (queryQualifier != null) ? queryQualifier
.andExp(entityQualifier) : entityQualifier;
}
setQualifier(entity.translateToRelatedEntity(queryQualifier, prefetchPath));
if (r.isToMany() && !r.isFlattened()) {
setLastPrefetchHint(r);
}
}
/**
* Creates a new disjoint prefetch select query.
*
* @since 1.2
*/
public PrefetchSelectQuery(SelectQuery parentQuery, String prefetchPath,
ObjRelationship lastPrefetchHint) {
setRoot(lastPrefetchHint.getTargetEntity());
this.parentQuery = parentQuery;
this.prefetchPath = prefetchPath;
this.lastPrefetchHint = lastPrefetchHint;
}
/**
* Overrides super implementation to suppress disjoint prefetch routing, as the parent
* query should take care of that.
*
* @since 1.2
*/
void routePrefetches(QueryRouter router, EntityResolver resolver) {
// noop - intentional.
}
/**
* Returns the prefetchPath.
*
* @return String
*/
public String getPrefetchPath() {
return prefetchPath;
}
/**
* Sets the prefetchPath.
*
* @param prefetchPath The prefetchPath to set
*/
public void setPrefetchPath(String prefetchPath) {
this.prefetchPath = prefetchPath;
}
/**
* @since 1.1
*/
public SelectQuery getParentQuery() {
return parentQuery;
}
/**
* @since 1.1
*/
public void setParentQuery(SelectQuery parentQuery) {
this.parentQuery = parentQuery;
}
/**
* Retunrs last incoming ObjRelationship in the prefetch relationship chain.
*
* @since 1.1
*/
public ObjRelationship getLastPrefetchHint() {
return lastPrefetchHint;
}
/**
* @since 1.1
*/
public void setLastPrefetchHint(ObjRelationship relationship) {
lastPrefetchHint = relationship;
}
/**
* Configures an "extra" path that will resolve to an extra column (or columns) in the
* result set.
*
* @param path A valid path expression. E.g. "abc" or "db:ABC" or "abc.xyz".
* @since 1.2
*/
public void addResultPath(String path) {
if (Util.isEmptyString(path)) {
throw new IllegalArgumentException("Invalid path: " + path);
}
nonNullResultPaths().add(path);
}
/**
* Removes an extra result path. Note that this method doesn't check for expression
* invariants, as it doesn't have a proper context to do so. E.g. for the purspose of
* this method "db:ARTIST_NAME" and "obj:artistName" are not the same, though both
* will resolve to the same column name.
*/
public void removeResultPath(String path) {
if (resultPaths != null) {
resultPaths.remove(path);
}
}
/**
* Returns extra result paths.
*
* @since 1.2
*/
public Collection getResultPaths() {
return resultPaths != null
? Collections.unmodifiableCollection(resultPaths)
: Collections.EMPTY_SET;
}
/**
* Returns a Collection that internally stores extra result paths, creating it on
* demand.
*
* @since 1.2
*/
Collection nonNullResultPaths() {
if (resultPaths == null) {
resultPaths = new HashSet();
}
return resultPaths;
}
}