org.eclipse.persistence.internal.expressions.ForUpdateClause Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of eclipselink Show documentation
EclipseLink build based upon Git transaction f2b9fc5
The newest version!
/*
 * Copyright (c) 1998, 2024 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.internal.expressions;

import org.eclipse.persistence.internal.helper.DatabaseTable;
import org.eclipse.persistence.queries.ObjectBuildingQuery;

import java.io.Serializable;
import java.util.Collection;
import java.util.HashSet;

/**
 * Purpose:Represents The FOR UPDATE pessimistically locking clause.
 *  @author  Stephen McRitchie
 *  @since   Oracle Toplink 10g AS
 */
public class ForUpdateClause implements Serializable, Cloneable {
    protected static final ForUpdateClause NO_LOCK_CLAUSE = new ForUpdateClause();
    short lockMode;
    Integer waitTimeout;

    public ForUpdateClause() {
        this.lockMode = ObjectBuildingQuery.NO_LOCK;
    }

    public ForUpdateClause(short lockMode) {
        this.lockMode = lockMode;
    }

    public ForUpdateClause(Integer waitTimeout) {
        this.lockMode = ObjectBuildingQuery.LOCK;
        this.waitTimeout = waitTimeout;
    }

    @Override
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException never) {
            return null;
        }
    }

    public static ForUpdateClause newInstance(short lockMode) {
        if (lockMode == ObjectBuildingQuery.NO_LOCK) {
            return NO_LOCK_CLAUSE;
        } else {
            return new ForUpdateClause(lockMode);
        }
    }

    public static ForUpdateClause newInstance(Integer waitTimeout) {
        return new ForUpdateClause(waitTimeout);
    }

    public boolean isForUpdateOfClause() {
        return false;
    }

    public boolean isReferenceClassLocked() {
        return true;
    }

    public short getLockMode() {
        return lockMode;
    }

    public Integer getWaitTimeout() {
        return waitTimeout;
    }

    /**
     * INTERNAL:
     * Prints the as of clause for an expression inside of the FROM clause.
     */
    public void printSQL(ExpressionSQLPrinter printer, SQLSelectStatement statement) {
        // Append lock strings
        if (getLockMode() == ObjectBuildingQuery.LOCK) {
            if (waitTimeout == null) {
                printer.printString(printer.getPlatform().getSelectForUpdateString());
            } else {
                printer.printString(printer.getPlatform().getSelectForUpdateWaitString(waitTimeout));
            }
        } else if (lockMode == ObjectBuildingQuery.LOCK_NOWAIT) {
            printer.printString(printer.getPlatform().getSelectForUpdateNoWaitString());
        }
    }

    /**
     * INTERNAL:
     * Returns collection of aliases of the tables to be locked.
     * Only used by platforms that lock tables individually in FROM clause
     * (platform.shouldPrintLockingClauseAfterWhereClause()==false)
     * like SQLServer
     */
    public Collection getAliasesOfTablesToBeLocked(SQLSelectStatement statement) {
        return new HashSet<>(statement.getTableAliases().keySet());
    }
}