OrExpressionStateObject.java

/*******************************************************************************
 * Copyright (c) 2011, 2015 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
 *
 ******************************************************************************/
package org.eclipse.persistence.jpa.jpql.tools.model.query;

import org.eclipse.persistence.jpa.jpql.parser.ConditionalExpressionBNF;
import org.eclipse.persistence.jpa.jpql.parser.ConditionalTermBNF;
import org.eclipse.persistence.jpa.jpql.parser.OrExpression;
import static org.eclipse.persistence.jpa.jpql.parser.Expression.*;

/**
 * The <code><b>OR</b></code> logical operator chains multiple criteria together. A valid operand
 * of an <code><b>OR</b></code> operator must be one of: <code><b>TRUE</b></code>,
 * <code><b>FALSE</b></code>, and <code><b>NULL</b></code>. The <code><b>OR</b></code> operator has
 * a lower precedence than the <code><b>AND</b></code> operator.
 * <p>
 * <code><b>NULL</b></code> represents unknown. Therefore, if one operand is <code><b>NULL</b></code>
 * and the other operand is <code><b>TRUE</b></code> the result is <code><b>TRUE</b></code>, because
 * one <code><b>TRUE</b></code> operand is sufficient for a <code><b>TRUE</b></code> result. If one
 * operand is <code><b>NULL</b></code> and the other operand is either <code><b>FALSE</b></code> or
 * <code><b>NULL</b></code>, the result is <code><b>NULL</b></code> (unknown).
 * <p>
 * The following table shows how the <b>OR</b> operator is evaluated based on its two operands:
 *
 * <table summary="" cellspacing="0" cellpadding="2" border="1" width="250" style="border:1px outset darkgrey;">
 * <tr><td></td><td><b>TRUE</b></td><td><b>FALSE</b></td><td><b>NULL</b></td></tr>
 * <tr><td><b>TRUE</b></td><td>TRUE</td><td>TRUE</td><td>TRUE</td></tr>
 * <tr><td><b>FALSE</b></td><td>TRUE</td><td>FALSE</td><td>NULL</td></tr>
 * <tr><td><b>NULL</b></td><td>TRUE</td><td>NULL</td><td>NULL</td></tr>
 * </table>
 *
 * <div><b>BNF:</b> <code>conditional_expression ::= conditional_expression OR conditional_term</code><p></div>
 *
 * @see OrExpression
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
public class OrExpressionStateObject extends LogicalExpressionStateObject {

    /**
     * Creates a new <code>OrExpressionStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    public OrExpressionStateObject(StateObject parent) {
        super(parent);
    }

    /**
     * Creates a new <code>OrExpressionStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param leftStateObject The {@link StateObject} representing the left expression
     * @param rightStateObject The {@link StateObject} representing the right expression
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    public OrExpressionStateObject(StateObject parent,
                                   StateObject leftStateObject,
                                   StateObject rightStateObject) {

        super(parent, leftStateObject, rightStateObject);
    }

    /**
     * Creates a new <code>OrExpressionStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param leftJpqlFragment The string representation of the left expression to parse and to
     * convert into a {@link StateObject}
     * @param rightJpqlFragment The string representation of the right expression to parse and to
     * convert into a {@link StateObject}
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    public OrExpressionStateObject(StateObject parent,
                                   String leftJpqlFragment,
                                   String rightJpqlFragment) {

        super(parent, leftJpqlFragment, rightJpqlFragment);
    }

    /**
     * {@inheritDoc}
     */
    public void accept(StateObjectVisitor visitor) {
        visitor.visit(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public OrExpression getExpression() {
        return (OrExpression) super.getExpression();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getIdentifier() {
        return OR;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected String getLeftQueryBNFId() {
        return ConditionalExpressionBNF.ID;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected String getRightQueryBNFId() {
        return ConditionalTermBNF.ID;
    }

    /**
     * Keeps a reference of the {@link OrExpression parsed object} object, which should only be
     * done when this object is instantiated during the conversion of a parsed JPQL query into
     * {@link StateObject StateObjects}.
     *
     * @param expression The {@link OrExpression parsed object} representing a logical
     * <code><b>OR</b></code> expression
     */
    public void setExpression(OrExpression expression) {
        super.setExpression(expression);
    }
}