org.eclipse.persistence.history.AsOfSCNClause 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
There is a newer version: 5.0.0-B03
/*
 * Copyright (c) 1998, 2024 Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2022 IBM Corporation. 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.history;

import org.eclipse.persistence.expressions.Expression;
import org.eclipse.persistence.internal.expressions.ConstantExpression;
import org.eclipse.persistence.internal.expressions.ExpressionSQLPrinter;
import org.eclipse.persistence.internal.helper.ClassConstants;
import org.eclipse.persistence.internal.helper.ConversionManager;

/**
 * Purpose:Wraps an immutable value for a past time, represented as a
 * database system change number.
 * 
 * This should be specified with an Oracle platform supporting flashback,
 * and the value will be written to the SQL FROM clause:
 * 
 * SELECT ... FROM EMPLOYEE AS OF SCN (value) t0, ...
 * @since OracleAS TopLink 10g (10.0.3)
 * @author Stephen McRitchie
 * @see AsOfClause
 * @see org.eclipse.persistence.platform.database.OraclePlatform#getSystemChangeNumberQuery
 */
public class AsOfSCNClause extends AsOfClause {
    public AsOfSCNClause(Number systemChangeNumber) {
        super(systemChangeNumber);
    }

    public AsOfSCNClause(Long systemChangeNumber) {
        super(systemChangeNumber);
    }

    public AsOfSCNClause(long systemChangeNumber) {
        super(Long.valueOf(systemChangeNumber));
    }

    public AsOfSCNClause(Expression expression) {
        super(expression);
    }

    /**
     * INTERNAL:
     * Prints the as of clause for an expression inside of the FROM clause.
     */
    @Override
    public void printSQL(ExpressionSQLPrinter printer) {
        printer.printString("AS OF SCN (");
        Object value = getValue();
        if (value instanceof Expression expression) {
            // Sort of an implementation of native sql.
            // Print AS OF SCN (1000L - 45L) not AS OF ('1000L - 45L').
            if ((value instanceof ConstantExpression ce) && (ce.getValue() instanceof String s)) {
                printer.printString(s);
            } else {
                printer.printExpression(expression);
            }
        } else {
            ConversionManager converter = ConversionManager.getDefaultManager();
            value = converter.convertObject(value, ClassConstants.LONG);
            printer.printPrimitive(value, true);
        }
        printer.printString(")");
    }

    /**
     * PUBLIC:
     */
    @Override
    public boolean isAsOfSCNClause() {
        return true;
    }
}