org.eclipse.persistence.descriptors.ChangedFieldsLockingPolicy Maven / Gradle / Ivy
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/*
* Copyright (c) 1998, 2018 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 v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// 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.*;
/**
* Purpose: 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.
* 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 getFieldsToCompare(DatabaseTable table, AbstractRecord transRow, AbstractRecord modifyRow) {
List fields = getAllNonPrimaryKeyFields(table);
List returnedFields = new ArrayList();
for (DatabaseField field : fields) {
if (modifyRow.containsKey(field)) {
returnedFields.add(field);
}
}
return returnedFields;
}
}