| /* |
| * Copyright (c) 1998, 2021 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.history; |
| |
| import java.io.*; |
| import org.eclipse.persistence.expressions.*; |
| import org.eclipse.persistence.internal.expressions.*; |
| import org.eclipse.persistence.internal.helper.*; |
| |
| /** |
| * <b>Purpose:</b>Wraps an immutable value for a past time. |
| * A session, query, or expression can be as of a past time. |
| * <p> |
| * For Oracle 9R2 Flasback corresponds to the sub clause which appears between |
| * the table and alias name in the FROM clause: |
| * <code>SELECT ... FROM EMPLOYEE AS OF TIMESTAMP (value) t0, ...</code> |
| * </p><p>For generic historical schema support, a special criteria can be added to |
| * the where clause for each table in a select: |
| * <code>((t0.ROW_START {@literal <=} value) AND ((t0.END IS NULL) OR (t1.END {@literal >} value)))</code> |
| * </p><p><b>Responsibilities:</b></p> |
| * <ul> |
| * <li>By default AsOfClause is a timestamp. To specify a system change number use AsOfSCNClause. |
| * <li>For Oracle 9R2 Flashback prints the correct AS OF clause before the alias name in the FROM clause. |
| * <li>Read-only: the wrapped value can not change. |
| * </ul> |
| * @since OracleAS TopLink 10<i>g</i> (10.0.3) |
| * @author Stephen McRitchie |
| * @see org.eclipse.persistence.expressions.Expression#asOf(AsOfClause) |
| * @see org.eclipse.persistence.queries.ObjectLevelReadQuery#setAsOfClause(AsOfClause) |
| * @see org.eclipse.persistence.sessions.Session#acquireHistoricalSession(AsOfClause) |
| * @see HistoryPolicy |
| */ |
| public class AsOfClause implements Serializable { |
| public static final AsOfClause NO_CLAUSE = new AsOfClause((Expression)null); |
| private Object value; |
| |
| protected AsOfClause() { |
| } |
| |
| public AsOfClause(java.util.Date date) { |
| this.value = date; |
| } |
| |
| public AsOfClause(java.sql.Timestamp timestamp) { |
| this.value = timestamp; |
| } |
| |
| public AsOfClause(java.util.Calendar calendar) { |
| this.value = calendar; |
| } |
| |
| public AsOfClause(long time) { |
| this.value = time; |
| } |
| |
| public AsOfClause(Long time) { |
| this.value = time; |
| } |
| |
| protected AsOfClause(Number number) { |
| this.value = number; |
| } |
| |
| public AsOfClause(Expression expression) { |
| this.value = expression; |
| } |
| |
| protected AsOfClause(AsOfClause wrappedValue) { |
| this.value = wrappedValue; |
| } |
| |
| /** |
| * INTERNAL: |
| * Return if the as of is equal to the other. |
| * Equality of asOf clauses is complex (with subclasses), |
| * so only use identity. |
| */ |
| @Override |
| public boolean equals(Object object) { |
| return this == object; |
| } |
| |
| /** |
| * INTERNAL: |
| * Prints the as of clause for an expression inside of the FROM clause. |
| */ |
| public void printSQL(ExpressionSQLPrinter printer) { |
| printer.printString("AS OF TIMESTAMP ("); |
| Object value = getValue(); |
| if (value instanceof Expression) { |
| // Sort of an implementation of native sql. |
| // Print AS OF TIMESTAMP (SYSDATE - 1000*60*10) not AS OF ('SYSDATE - 1000*60*10'). |
| if ((value instanceof ConstantExpression) && (((ConstantExpression)value).getValue() instanceof String)) { |
| printer.printString((String)((ConstantExpression)value).getValue()); |
| } else { |
| printer.printExpression((Expression)value); |
| } |
| } else { |
| ConversionManager converter = ConversionManager.getDefaultManager(); |
| value = converter.convertObject(value, ClassConstants.TIMESTAMP); |
| printer.printPrimitive(value); |
| } |
| printer.printString(")"); |
| } |
| |
| /** |
| * PUBLIC: |
| * The past time represented by the receiver. Either a timestamp, a system |
| * change number, or an Expression. |
| */ |
| public Object getValue() { |
| return value; |
| } |
| |
| /** |
| * PUBLIC: |
| * Indicates that <code>value</code> is a system change number or an expression |
| * evaluating to one. |
| * <p>In Oracle the value will have to be printed using the syntax <code>AS OF SCN(value)</code> |
| * instead of <code>AS OF TIMESTAMP(value)</code>. |
| * @see AsOfSCNClause |
| */ |
| public boolean isAsOfSCNClause() { |
| return false; |
| } |
| |
| /** |
| * PUBLIC: |
| * Answers if this is a UniversalAsOfClause, one to be applied |
| * to the entire selection criteria. |
| * <p>Used when a query is made as of a past time. |
| */ |
| public boolean isUniversal() { |
| return false; |
| } |
| |
| @Override |
| public String toString() { |
| StringWriter writer = new StringWriter(); |
| writer.write(Helper.getShortClassName(getClass())); |
| writer.write("("); |
| writer.write(String.valueOf(getValue())); |
| writer.write(")"); |
| return writer.toString(); |
| } |
| } |