/*****************************************************************
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* 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,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
****************************************************************/
package org.apache.cayenne.query;
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;
import org.apache.cayenne.reflect.ArcProperty;
import org.apache.cayenne.reflect.ClassDescriptor;
import org.apache.cayenne.util.Util;
/**
* A query that selects objects related to a given object via a mapped relationship.
* RelationshipQuery is used by Cayenne internally to resolve relationships, and is rarely
* executed by the application directly, although this of course is possible too.
*
* @since 1.2
*/
public class RelationshipQuery extends IndirectQuery {
protected ObjectId objectId;
protected String relationshipName;
protected boolean refreshing;
protected int statementFetchSize;
protected transient EntityResolver metadataResolver;
protected transient QueryMetadata metadata;
protected transient ArcProperty arc;
// exists for deserialization with Hessian
@SuppressWarnings("unused")
private RelationshipQuery() {
}
/**
* Creates a RelationshipQuery. Same as
* <em>new RelationshipQuery(objectID, relationshipName, true)</em>.
*
* @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.)
@Override
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;
}
@Override
protected Query createReplacementQuery(EntityResolver resolver) {
if (objectId.isTemporary() && !objectId.isReplacementIdAttached()) {
throw new CayenneRuntimeException("Can't build a query for relationship '%s' for temporary id: %s"
, relationshipName, objectId);
}
ObjRelationship relationship = getRelationship(resolver);
// build executable select...
Expression qualifier = ExpressionFactory.matchDbExp(relationship
.getReverseDbRelationshipPath(), objectId);
SelectQuery<Object> query = new SelectQuery<Object>(
(ObjEntity) relationship.getTargetEntity(),
qualifier);
query.setStatementFetchSize(statementFetchSize);
return query;
}
/**
* Returns a non-null relationship object for this query.
*/
public ObjRelationship getRelationship(EntityResolver resolver) {
updateMetadata(resolver);
return arc.getRelationship();
}
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.");
}
ClassDescriptor descriptor = resolver.getClassDescriptor(objectId
.getEntityName());
this.arc = (ArcProperty) descriptor.getProperty(relationshipName);
if (arc == null) {
throw new CayenneRuntimeException("No relationship named %s found in entity %s; object id: %s"
, relationshipName, objectId.getEntityName(), objectId);
}
this.metadata = new DefaultQueryMetadata() {
@Override
public boolean isRefreshingObjects() {
return refreshing;
}
@Override
public ObjEntity getObjEntity() {
return arc.getTargetDescriptor().getEntity();
}
@Override
public ClassDescriptor getClassDescriptor() {
return arc.getTargetDescriptor();
}
@Override
public int getStatementFetchSize() {
return statementFetchSize;
}
};
this.metadataResolver = resolver;
}
}
/**
* Sets statement's fetch size (0 for no default size)
*
* @since 3.0
*/
public void setStatementFetchSize(int size) {
this.statementFetchSize = size;
}
/**
* @return statement's fetch size
* @since 3.0
*/
public int getStatementFetchSize() {
return statementFetchSize;
}
/**
* Overrides toString() outputting a short string with query class and relationship
* name.
*/
@Override
public String toString() {
return Util.stripPackageName(getClass().getName()) + ":" + getRelationshipName();
}
}