/******************************************************************************* | |
* Copyright (c) 1998, 2013 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.descriptors; | |
import java.util.*; | |
import org.eclipse.persistence.mappings.*; | |
import org.eclipse.persistence.mappings.DatabaseMapping.WriteType; | |
import org.eclipse.persistence.internal.helper.*; | |
import org.eclipse.persistence.internal.sessions.AbstractRecord; | |
import org.eclipse.persistence.queries.*; | |
import org.eclipse.persistence.expressions.*; | |
/** | |
* <p><b>Purpose</b>: An implementation of the OptimisticLockingPolicy interface. | |
* This policy compares only the changed fields in the WHERE clause | |
* when doing an update. If any field has been changed, an optimistic | |
* locking exception will be thrown. A delete will only compare | |
* the primary key. <p> | |
* NOTE: This policy can only be used inside a unit of work. | |
* | |
* @since TopLink 2.1 | |
* @author Peter Krogh | |
*/ | |
public class ChangedFieldsLockingPolicy extends FieldsLockingPolicy { | |
/** | |
* PUBLIC: | |
* Create a new changed fields locking policy. | |
* This locking policy is based on locking on all changed fields by comparing with | |
* their previous values to detect field-level collisions. | |
* | |
* Note: the unit of work must be used for all updates when using field locking. Without | |
* a unit of work, there is no way for to know what the original values were | |
* without the back up clone in the unit of work. | |
*/ | |
public ChangedFieldsLockingPolicy() { | |
super(); | |
} | |
/** | |
* INTERNAL: | |
* Values to be included in the locking mechanism are added to the translation row. | |
* For changed fields the normal build row is ok as only changed fields matter. | |
*/ | |
@Override | |
public void addLockValuesToTranslationRow(ObjectLevelModifyQuery query) { | |
verifyUsage(query.getSession()); | |
Object object; | |
if (query.isDeleteObjectQuery()) { | |
return; | |
} | |
object = query.getBackupClone(); | |
// EL bug 319759 | |
if (query.isUpdateObjectQuery()) { | |
query.setShouldValidateUpdateCallCacheUse(true); | |
} | |
for (Enumeration enumtr = query.getModifyRow().keys(); enumtr.hasMoreElements();) { | |
DatabaseField field = (DatabaseField)enumtr.nextElement(); | |
DatabaseMapping mapping = descriptor.getObjectBuilder().getMappingForField(field); | |
mapping.writeFromObjectIntoRow(object, query.getTranslationRow(), query.getSession(), WriteType.UNDEFINED); | |
} | |
} | |
/** | |
* INTERNAL: | |
* When given an expression, this method will return a new expression with the optimistic | |
* locking values included. The values are taken from the passed in database row. | |
* This expression will be used in a delete call. | |
* No new criteria will be added for changed fields. | |
*/ | |
@Override | |
public Expression buildDeleteExpression(DatabaseTable table, Expression mainExpression, AbstractRecord row) { | |
return mainExpression; | |
} | |
/** | |
* INTERNAL: | |
* Returns the fields that should be compared in the where clause. | |
* In this case, it is only the fields that were changed. | |
*/ | |
@Override | |
protected List<DatabaseField> getFieldsToCompare(DatabaseTable table, AbstractRecord transRow, AbstractRecord modifyRow) { | |
List<DatabaseField> fields = getAllNonPrimaryKeyFields(table); | |
List<DatabaseField> returnedFields = new ArrayList<DatabaseField>(); | |
for (DatabaseField field : fields) { | |
if (modifyRow.containsKey(field)) { | |
returnedFields.add(field); | |
} | |
} | |
return returnedFields; | |
} | |
} |