| /* |
| * Copyright (c) 1998, 2020 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 java.util.*; |
| import org.eclipse.persistence.expressions.*; |
| |
| /** |
| * Used to itterate an expression tree, through inner subclasses. |
| */ |
| public abstract class ExpressionIterator { |
| |
| /** Allow the iteration to build a result. */ |
| protected Object result; |
| |
| /** Some iterations require a statement. */ |
| protected SQLSelectStatement statement; |
| |
| /** Some iterations require a more general parameter. */ |
| protected Object parameter; |
| |
| /** |
| * Block constructor comment. |
| */ |
| public ExpressionIterator() { |
| super(); |
| } |
| |
| public Object getResult() { |
| return result; |
| } |
| |
| public SQLSelectStatement getStatement() { |
| return statement; |
| } |
| |
| /** |
| * Answers if this expression has already been visited. |
| * For a faster iteration override to insure expressions are only |
| * visited/processed once. |
| */ |
| public boolean hasAlreadyVisited(Expression expression) { |
| return false; |
| } |
| |
| /** |
| * INTERNAL: |
| * This method must be defined by subclasses to implement the logic of the iteratation. |
| */ |
| public abstract void iterate(Expression expression); |
| |
| /** |
| * INTERNAL: |
| */ |
| public void iterateOn(Vector expressions) { |
| for (Enumeration expressionEnum = expressions.elements(); expressionEnum.hasMoreElements();) { |
| iterate((Expression)expressionEnum.nextElement()); |
| } |
| } |
| |
| /** |
| * INTERNAL: |
| * Return the call. |
| */ |
| public void iterateOn(Expression expression) { |
| expression.iterateOn(this); |
| } |
| |
| public void setResult(Object result) { |
| this.result = result; |
| } |
| |
| public void setStatement(SQLSelectStatement statement) { |
| this.statement = statement; |
| } |
| |
| /** |
| * Normally an Iterator will not go into the where clause of |
| * an SQLSubSelectExpression. I.e. when aliasing the parent statement |
| * is aliased before the subselects may even be normalized. An iterator to |
| * alias the SubSelect must be run later. |
| */ |
| public boolean shouldIterateOverSubSelects() { |
| return false; |
| } |
| } |