/*******************************************************************************
* Copyright (c) 1998, 2016 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.internal.indirection;
import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.exceptions.DatabaseException;
import org.eclipse.persistence.exceptions.ValidationException;
import org.eclipse.persistence.internal.sessions.AbstractRecord;
import org.eclipse.persistence.internal.sessions.AbstractSession;
import org.eclipse.persistence.internal.sessions.UnitOfWorkImpl;
import org.eclipse.persistence.mappings.AttributeAccessor;
import org.eclipse.persistence.mappings.DatabaseMapping;
import org.eclipse.persistence.mappings.ForeignReferenceMapping;
import org.eclipse.persistence.queries.ObjectBuildingQuery;
import org.eclipse.persistence.queries.ObjectLevelReadQuery;
import org.eclipse.persistence.queries.ReadQuery;
/**
* QueryBasedValueHolder wraps a database-stored object and implements behavior
* to access it. The object is read from the database by invoking a
* user-specified query.
*
* @see ObjectLevelReadQuery
* @author Dorin Sandu
*/
public class QueryBasedValueHolder extends DatabaseValueHolder {
/**
* Stores the query to be executed.
*/
protected transient ReadQuery query;
protected transient Object sourceObject;
protected Integer refreshCascade;
protected QueryBasedValueHolder() {
}
/**
* Initialize the query-based value holder.
*/
public QueryBasedValueHolder(ReadQuery query, AbstractRecord row, AbstractSession session) {
this(query, null, row, session);
}
/**
/**
* Store the uow identity so that it can be used to determine new
* transaction logic
*/
/**
* Initialize the query-based value holder.
*/
public QueryBasedValueHolder(ReadQuery query, Object sourceObject, AbstractRecord row, AbstractSession session) {
this.row = row;
this.session = session;
// Make sure not to put a ClientSession or IsolatedClientSession in
// the shared cache (indirectly).
// Skip this if unitOfWork, for we use session.isUnitOfWork() to
// implement
// isTransactionalValueholder(), saving us from needing a boolean
// instance variable.
// If unitOfWork this safety measure is deferred until merge time with
// releaseWrappedValuehHolder.
// Note that if isolated session & query will return itself, which is
// safe
// for if isolated it will not go in the shared cache.
if (!session.isUnitOfWork()) {
this.session = session.getRootSession(query);
}
this.query = query;
this.sourceObject = sourceObject;
}
/**
* INTERNAL:
* Returns the refresh cascade policy that was set on the query that was used to instantiate the valueholder
* a null value means that a non refresh query was used.
*/
public Integer getRefreshCascadePolicy(){
return this.refreshCascade;
}
/**
* Process against the UOW and attempt to load a local copy before going to the shared cache
* If null is returned then the calling UOW will instantiate as normal.
*/
@Override
public Object getValue(UnitOfWorkImpl uow) {
if (this.query.isReadObjectQuery()){
return this.query.getQueryMechanism().checkCacheForObject(this.query.getTranslationRow(), uow);
}
//not able to shortcircuit cache lookup to UOW return null;
return null;
}
/**
* Return the query. The query for a QueryBasedValueHolder is constructed
* dynamically based on the original query on the parent object and the
* mapping configuration. If modifying a query the developer must be careful
* not to change the results returned as that may cause the application to
* see incorrect results.
*/
public ReadQuery getQuery() {
return query;
}
protected Object instantiate() throws DatabaseException {
return instantiate(this.session);
}
/**
* Instantiate the object by executing the query on the session.
*/
protected Object instantiate(AbstractSession session) throws DatabaseException {
if (session == null) {
throw ValidationException.instantiatingValueholderWithNullSession();
}
if (this.query.isObjectBuildingQuery() && ((ObjectBuildingQuery)this.query).shouldRefreshIdentityMapResult()){
this.refreshCascade = ((ObjectBuildingQuery)this.query).getCascadePolicy();
}
Object result = session.executeQuery(getQuery(), getRow());
// Bug 489898 - ensure that the query's session is dereferenced, post-execution
getQuery().setSession(null);
return result;
}
/**
* Triggers UnitOfWork valueholders directly without triggering the wrapped
* valueholder (this).
* <p>
* When in transaction and/or for pessimistic locking the
* UnitOfWorkValueHolder needs to be triggered directly without triggering
* the wrapped valueholder. However only the wrapped valueholder knows how
* to trigger the indirection, i.e. it may be a batchValueHolder, and it
* stores all the info like the row and the query. Note: This method is not
* thread-safe. It must be used in a synchronized manner
*/
public Object instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder unitOfWorkValueHolder) {
return instantiate(unitOfWorkValueHolder.getUnitOfWork());
}
/**
* INTERNAL:
* Run any extra code required after the valueholder instantiates
* For query based VH, we notify the cache that the valueholder has been triggered
*/
public void postInstantiate(){
DatabaseMapping mapping = query.getSourceMapping();
if (mapping != null && mapping.isForeignReferenceMapping()){
// Fix for Bug#474232
ClassDescriptor descriptor = mapping.getDescriptor();
final IndirectionPolicy indirectionPolicy = ((ForeignReferenceMapping) mapping).getIndirectionPolicy();
if (indirectionPolicy != null && indirectionPolicy.isWeavedObjectBasicIndirectionPolicy()) {
if (!isCoordinatedWithProperty && mapping.isObjectReferenceMapping() && sourceObject != null && value != null) {
// Bug#487930
Object object = sourceObject;
if (descriptor != null && descriptor.isAggregateDescriptor()) {
// navigate to the leaf element in the accessor tree
for(AttributeAccessor accessor : descriptor.getAccessorTree()) {
object = accessor.getAttributeValueFromObject(object);
}
}
mapping.setAttributeValueInObject(object, this);
isCoordinatedWithProperty = true;
}
}
if (descriptor == null || descriptor.isAggregateDescriptor()){
descriptor = session.getDescriptor(sourceObject);
}
if (descriptor != null){
session.getIdentityMapAccessorInstance().getIdentityMap(descriptor).lazyRelationshipLoaded(sourceObject, this, (ForeignReferenceMapping)query.getSourceMapping());
}
}
}
/**
* Releases a wrapped valueholder privately owned by a particular unit of
* work.
* <p>
* When unit of work clones are built directly from rows no object in the
* shared cache points to this valueholder, so it can store the unit of work
* as its session. However once that UnitOfWork commits and the valueholder
* is merged into the shared cache, the session needs to be reset to the
* root session, ie. the server session.
*/
@Override
public void releaseWrappedValueHolder(AbstractSession targetSession) {
AbstractSession session = getSession();
if ((session != null) && session.isUnitOfWork()) {
setSession(targetSession);
}
}
/**
* Reset all the fields that are not needed after instantiation.
*/
protected void resetFields() {
super.resetFields();
this.query = null;
}
/**
* Set the query.
*/
protected void setQuery(ReadQuery theQuery) {
query = theQuery;
}
/**
* INTERNAL: Answers if this valueholder is a pessimistic locking one. Such
* valueholders are special in that they can be triggered multiple times by
* different UnitsOfWork. Each time a lock query will be issued. Hence even
* if instantiated it may have to be instantiated again, and once
* instantiated all fields can not be reset.
* <p>
* Since locks will be issued each time this valueholder is triggered,
* triggering this directly on the session in auto commit mode will generate
* an exception. This only UnitOfWorkValueHolder's wrapping this can trigger
* it. Note: This method is not thread-safe. It must be used in a
* synchronized manner
*/
public boolean isPessimisticLockingValueHolder() {
// Get the easy checks out of the way first.
if ((this.query == null) || !this.query.isObjectLevelReadQuery()) {
return false;
}
ObjectLevelReadQuery query = (ObjectLevelReadQuery) this.query;
// Note even if the reference class is not locked, but the valueholder
// query
// has joined attributes, then this may count as a lock query.
// This means it is possible to trigger a valueholder to get an object
// which
// is not to be pess. locked and get an exception for triggering it on
// the
// session outside a transaction.
return query.isLockQuery(this.session);
}
public void setSourceObject(Object sourceObject) {
this.sourceObject = sourceObject;
}
/**
* INTERNAL:
* @param refreshCascadePolicy
* @return
*/
public void setRefreshCascadePolicy(Integer refreshCascadePolicy) {
this.refreshCascade = refreshCascadePolicy;
}
}