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Cayenne Object Persistence Framework
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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
* with the License. You may obtain a copy of the License at
*
* 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 org.apache.commons.lang.StringUtils;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.ObjectId;
import org.apache.cayenne.exp.Expression;
import org.apache.cayenne.exp.ExpressionFactory;
import org.apache.cayenne.map.EntityResolver;
import org.apache.cayenne.map.ObjEntity;
import org.apache.cayenne.map.ObjRelationship;
/**
* A query that selects objects related to a given object. It is intended for fetching
* objects related to a given object using a mapped relationship. Cayenne uses it for this
* purpose internally. RelationshipQuery works with either an ObjectId or a GlobalID for a
* root object.
*
* @since 1.2
* @author Andrus Adamchik
*/
public class RelationshipQuery extends IndirectQuery {
protected ObjectId objectId;
protected String relationshipName;
protected boolean refreshing;
protected transient EntityResolver metadataResolver;
protected transient QueryMetadata metadata;
protected transient ObjRelationship relationship;
// exists for deserialization with Hessian
private RelationshipQuery() {
}
/**
* Creates a RelationshipQuery. Same as
* new RelationshipQuery(objectID, relationshipName, true).
*
* @param objectID ObjectId of a root object of the relationship.
* @param relationshipName The name of the relationship.
*/
public RelationshipQuery(ObjectId objectID, String relationshipName) {
this(objectID, relationshipName, true);
}
/**
* Creates a RelationshipQuery.
*
* @param objectID ObjectId of a root object of the relationship.
* @param relationshipName The name of the relationship.
* @param refreshing whether objects should be refreshed
*/
public RelationshipQuery(ObjectId objectID, String relationshipName,
boolean refreshing) {
if (objectID == null) {
throw new CayenneRuntimeException("Null objectID");
}
this.objectId = objectID;
this.relationshipName = relationshipName;
this.refreshing = refreshing;
}
/**
* Returns query metadata object.
*/
// return metadata without creating replacement, as this is not always possible to
// create replacement (one-way relationships, etc.)
public QueryMetadata getMetaData(final EntityResolver resolver) {
updateMetadata(resolver);
return metadata;
}
public ObjectId getObjectId() {
return objectId;
}
public boolean isRefreshing() {
return refreshing;
}
public String getRelationshipName() {
return relationshipName;
}
protected Query createReplacementQuery(EntityResolver resolver) {
if (objectId.isTemporary() && !objectId.isReplacementIdAttached()) {
throw new CayenneRuntimeException("Can't build a query for relationship '"
+ relationshipName
+ "' for temporary id: "
+ objectId);
}
ObjRelationship relationship = getRelationship(resolver);
// build executable select...
Expression qualifier = ExpressionFactory.matchDbExp(relationship
.getReverseDbRelationshipPath(), objectId);
SelectQuery query = new SelectQuery(
(ObjEntity) relationship.getTargetEntity(),
qualifier);
query.setRefreshingObjects(refreshing);
return query;
}
/**
* Returns a non-null relationship object for this query.
*/
public ObjRelationship getRelationship(EntityResolver resolver) {
updateMetadata(resolver);
return relationship;
}
void updateMetadata(EntityResolver resolver) {
// caching metadata as it may be accessed multiple times (at a DC and DD level)
if (metadataResolver != resolver) {
if (objectId == null) {
throw new CayenneRuntimeException(
"Can't resolve query - objectID is null.");
}
ObjEntity entity = resolver.lookupObjEntity(objectId.getEntityName());
this.relationship = (ObjRelationship) entity
.getRelationship(relationshipName);
if (relationship == null) {
throw new CayenneRuntimeException("No relationship named "
+ relationshipName
+ " found in entity "
+ entity.getName()
+ "; object id: "
+ objectId);
}
this.metadata = new DefaultQueryMetadata() {
public boolean isRefreshingObjects() {
return refreshing;
}
public ObjEntity getObjEntity() {
return (ObjEntity) relationship.getTargetEntity();
}
};
this.metadataResolver = resolver;
}
}
/**
* Overrides toString() outputting a short string with query class and relationship
* name.
*/
public String toString() {
return StringUtils.substringAfterLast(getClass().getName(), ".")
+ ":"
+ getRelationshipName();
}
}
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