All Downloads are FREE. Search and download functionalities are using the official Maven repository.

oracle.toplink.essentials.internal.expressions.ExpressionIterator Maven / Gradle / Ivy

There is a newer version: 2.1-60f
Show newest version
/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * // Copyright (c) 1998, 2007, Oracle. All rights reserved.
 * 
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */
package oracle.toplink.essentials.internal.expressions;

import java.util.*;
import oracle.toplink.essentials.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;
    }
}




© 2015 - 2024 Weber Informatics LLC | Privacy Policy