| /* |
| * Copyright (c) 2012, 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 |
| // |
| package org.eclipse.persistence.jpa.jpql.parser; |
| |
| import java.util.Collection; |
| import java.util.List; |
| import org.eclipse.persistence.jpa.jpql.ExpressionTools; |
| import org.eclipse.persistence.jpa.jpql.WordParser; |
| |
| /** |
| * <p>An <code><b>AS OF</b></code> clause is part of a flashback query, which provides ways to view |
| * past states of database objects, or to return database objects to a previous state, without using |
| * traditional point-in-time recovery. |
| * </p><p> |
| * Specify <code><b>AS OF</b></code> to retrieve the single version of the rows returned by the |
| * query at a particular change number (SCN) or timestamp. If you specify SCN, then the expression |
| * must evaluate to a number. If you specify <code><b>TIMESTAMP</b></code>, then the expression must |
| * evaluate to a timestamp value. Oracle Database returns rows as they existed at the specified |
| * system change number or time. |
| * </p> |
| * <div><b>BNF:</b> <code>asof_clause ::= AS OF { SCN | TIMESTAMP } scalar_expression</code></div> |
| * |
| * @version 2.5 |
| * @since 2.5 |
| * @author Pascal Filion |
| */ |
| public final class AsOfClause extends AbstractExpression { |
| |
| /** |
| * The {@link Expression} representing the timestamp or change number. |
| */ |
| private AbstractExpression expression; |
| |
| /** |
| * Determines whether a whitespace was found after either <code><b>SCN</b></code> or |
| * <code><b>TIMESTAMP</b></code>. |
| */ |
| private boolean hasSpaceAfterCategory; |
| |
| /** |
| * Determines whether a whitespace was found after <code><b>AS OF</b></code>. |
| */ |
| private boolean hasSpaceAfterIdentifier; |
| |
| /** |
| * The actual identifier found in the string representation of the JPQL query. |
| */ |
| private String identifier; |
| |
| /** |
| * The actual <code><b>SCN</b></code> identifier found in the string representation of the |
| * JPQL query. |
| */ |
| private String scnIdentifier; |
| |
| /** |
| * The actual <code><b>TIMESTAMP</b></code> identifier found in the string representation of the |
| * JPQL query. |
| */ |
| private String timestampIdentifier; |
| |
| /** |
| * Creates a new <code>AsOfClause</code>. |
| * |
| * @param parent The parent of this expression |
| */ |
| public AsOfClause(AbstractExpression parent) { |
| super(parent, AS_OF); |
| } |
| |
| @Override |
| public void accept(ExpressionVisitor visitor) { |
| acceptUnknownVisitor(visitor); |
| } |
| |
| @Override |
| public void acceptChildren(ExpressionVisitor visitor) { |
| getExpression().accept(visitor); |
| } |
| |
| @Override |
| protected void addChildrenTo(Collection<Expression> children) { |
| children.add(getExpression()); |
| } |
| |
| @Override |
| protected void addOrderedChildrenTo(List<Expression> children) { |
| |
| // 'AS OF' |
| children.add(buildStringExpression(AS_OF)); |
| |
| if (hasSpaceAfterIdentifier) { |
| children.add(buildStringExpression(SPACE)); |
| } |
| |
| // 'SCN' |
| if (scnIdentifier != null) { |
| children.add(buildStringExpression(SCN)); |
| } |
| // 'TIMESTAMP' |
| else if (timestampIdentifier != null) { |
| children.add(buildStringExpression(TIMESTAMP)); |
| } |
| |
| if (hasSpaceAfterCategory) { |
| children.add(buildStringExpression(SPACE)); |
| } |
| |
| // Expression |
| if (expression != null) { |
| children.add(expression); |
| } |
| } |
| |
| @Override |
| public JPQLQueryBNF findQueryBNF(Expression expression) { |
| |
| if ((this.expression != null) && this.expression.isAncestor(expression)) { |
| return getQueryBNF(ScalarExpressionBNF.ID); |
| } |
| |
| return super.findQueryBNF(expression); |
| } |
| |
| /** |
| * Returns the actual <b>AS OF</b> identifier found in the string representation of the JPQL |
| * query, which has the actual case that was used. |
| * |
| * @return The <b>AS OF</b> identifier that was actually parsed |
| */ |
| public String getActualIdentifier() { |
| return identifier; |
| } |
| |
| /** |
| * Returns the actual <b>SCN</b> identifier found in the string representation of the JPQL query, |
| * which has the actual case that was used. |
| * |
| * @return The <b>SCN</b> identifier that was actually parsed, or an empty string if it was not parsed |
| */ |
| public String getActualScnIdentifier() { |
| return (scnIdentifier != null) ? scnIdentifier : ExpressionTools.EMPTY_STRING; |
| } |
| |
| /** |
| * Returns the actual <b>TIMESTAMP</b> identifier found in the string representation of the JPQL |
| * query, which has the actual case that was used. |
| * |
| * @return The <b>TIMESTAMP</b> identifier that was actually parsed, or an empty string if it was |
| * not parsed |
| */ |
| public String getActualTimestampIdentifier() { |
| return (timestampIdentifier != null) ? timestampIdentifier : ExpressionTools.EMPTY_STRING; |
| } |
| |
| /** |
| * Returns the {@link Expression} representing the timestamp or change number. |
| * |
| * @return The {@link Expression} that was parsed representing the timestamp or change number |
| */ |
| public Expression getExpression() { |
| if (expression == null) { |
| expression = buildNullExpression(); |
| } |
| return expression; |
| } |
| |
| @Override |
| public JPQLQueryBNF getQueryBNF() { |
| return getQueryBNF(AsOfClauseBNF.ID); |
| } |
| |
| /** |
| * Determines whether the {@link Expression} representing the timestamp or change number was |
| * parsed or not. |
| * |
| * @return <code>true</code> if the timestamp or change number was parsed; <code>false</code> otherwise |
| */ |
| public boolean hasExpression() { |
| return expression != null && |
| !expression.isNull(); |
| } |
| |
| /** |
| * Determines whether the identifier <b>SCN</b> was part of the query. |
| * |
| * @return <code>true</code> if the identifier <b>SCN</b> was parsed; <code>false</code> otherwise |
| */ |
| public boolean hasScn() { |
| return scnIdentifier != null; |
| } |
| |
| /** |
| * Determines whether a whitespace was found after either <b>SCN</b> or <code>TIMESTAMP</code>. |
| * |
| * @return <code>true</code> if there was a whitespace after <b>SCN</b> or <code>TIMESTAMP</code>; |
| * <code>false</code> otherwise |
| */ |
| public boolean hasSpaceAfterCategory() { |
| return hasSpaceAfterCategory; |
| } |
| |
| /** |
| * Determines whether a whitespace was found after <b>AS OF</b>. |
| * |
| * @return <code>true</code> if there was a whitespace after <b>AS OF</b>; <code>false</code> otherwise |
| */ |
| public boolean hasSpaceAfterIdentifier() { |
| return hasSpaceAfterIdentifier; |
| } |
| |
| /** |
| * Determines whether the identifier <b>TIMESTAMP</b> was part of the query. |
| * |
| * @return <code>true</code> if the identifier <b>TIMESTAMP</b> was parsed; <code>false</code> otherwise |
| */ |
| public boolean hasTimestamp() { |
| return timestampIdentifier != null; |
| } |
| |
| @Override |
| protected void parse(WordParser wordParser, boolean tolerant) { |
| |
| // 'AS OF' |
| identifier = wordParser.moveForwardIgnoreWhitespace(AS_OF); |
| hasSpaceAfterIdentifier = wordParser.skipLeadingWhitespace() > 0; |
| |
| // 'SCN' |
| if (wordParser.startsWithIdentifier(SCN)) { |
| scnIdentifier = wordParser.moveForward(SCN); |
| hasSpaceAfterCategory = wordParser.skipLeadingWhitespace() > 0; |
| } |
| // 'TIMESTAMP' |
| else if (wordParser.startsWithIdentifier(TIMESTAMP)) { |
| timestampIdentifier = wordParser.moveForward(TIMESTAMP); |
| hasSpaceAfterCategory = wordParser.skipLeadingWhitespace() > 0; |
| } |
| |
| // Expression |
| expression = parse(wordParser, ScalarExpressionBNF.ID, tolerant); |
| } |
| |
| @Override |
| protected void toParsedText(StringBuilder writer, boolean actual) { |
| |
| // 'AS OF' |
| writer.append(actual ? identifier : AS_OF); |
| |
| if (hasSpaceAfterIdentifier) { |
| writer.append(SPACE); |
| } |
| |
| // 'SCN' |
| if (scnIdentifier != null) { |
| writer.append(actual ? scnIdentifier : SCN); |
| } |
| |
| // 'TIMESTAMP' |
| if (timestampIdentifier != null) { |
| writer.append(actual ? timestampIdentifier : TIMESTAMP); |
| } |
| |
| if (hasSpaceAfterCategory) { |
| writer.append(SPACE); |
| } |
| |
| // Expression |
| if (expression != null) { |
| expression.toParsedText(writer, actual); |
| } |
| } |
| } |