foundation/org.eclipse.persistence.core/src/org/eclipse/persistence/internal/jpa/parsing/MinusNode.java

/*******************************************************************************
 * Copyright (c) 1998, 2013 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 v1.0 and Eclipse Distribution License v. 1.0 
 * which accompanies this distribution. 
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
 ******************************************************************************/  
package org.eclipse.persistence.internal.jpa.parsing;

import org.eclipse.persistence.expressions.*;
import org.eclipse.persistence.queries.ObjectLevelReadQuery;
import org.eclipse.persistence.queries.ReportQuery;

/**
 * INTERNAL
 * <p><b>Purpose</b>: Represent a '-' in EJBQL
 * <p><b>Responsibilities</b>:<ul>
 * <li> Generate the correct expression for a '-'
 * </ul>
 *    @author Jon Driscoll and Joel Lucuik
 *    @since July 2003
 */
public class MinusNode extends BinaryOperatorNode implements AliasableNode {
    public MinusNode() {
        super();
    }


    /**
     * INTERNAL
     * Apply this node to the passed query
     */
    public void applyToQuery(ObjectLevelReadQuery theQuery, GenerationContext context) {
        if (theQuery.isReportQuery()) {
            ReportQuery reportQuery = (ReportQuery)theQuery;
            reportQuery.addAttribute("minus", generateExpression(context), (Class)getType());
        }
    }
    
    /**
     * INTERNAL
     * Validate node and calculates its type.
     */
    public void validate(ParseTreeContext context) {
        super.validate(context);
        if ((left != null) && (right != null)) {
            TypeHelper typeHelper = context.getTypeHelper();
            setType(typeHelper.extendedBinaryNumericPromotion(
                        left.getType(), right.getType()));
        }
    }

    /**
     * INTERNAL
     * Generate the expression. The steps are:
     * 1. Generate the expression for the left node
     * 2. Add the .subtract to the where clause returned from step 1
     * 3. Generate the expression for the right side and use it as the parameter for the .subtract()
     * 4. Return the completed where clause to the caller
     */
    public Expression generateExpression(GenerationContext context) {
        Expression whereClause = getLeft().generateExpression(context);
        whereClause = ExpressionMath.subtract(whereClause, getRight().generateExpression(context));
        return whereClause;
    }

    public boolean isMinusNode() {
        return true;
    }
    
    public boolean isAliasableNode(){
        return true;
    }
}