CountFunction.java

/*******************************************************************************
 * Copyright (c) 2006, 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.parser;

import org.eclipse.persistence.jpa.jpql.WordParser;

/**
 * One of the aggregate functions. The return type of this function is a <code>Long</code>.
 *
 * <div><b>BNF:</b> <code>expression ::= COUNT ([DISTINCT] identification_variable |
 *                                                                state_field_path_expression |
 *                                                                single_valued_object_path_expression)</code><p></div>
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public final class CountFunction extends AggregateFunction {

    /**
     * Creates a new <code>CountFunction</code>.
     *
     * @param parent The parent of this expression
     */
    public CountFunction(AbstractExpression parent) {
        super(parent, COUNT);
    }

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

    /**
     * {@inheritDoc}
     */
    @Override
    protected AbstractExpression buildEncapsulatedExpression(WordParser wordParser, String word) {

        if (KEY.equalsIgnoreCase(word)) {
            ExpressionFactory factory = getExpressionFactory(KeyExpressionFactory.ID);
            return factory.buildExpression(this, wordParser, word, getQueryBNF(), null, false);
        }

        if (VALUE.equalsIgnoreCase(word)) {
            ExpressionFactory factory = getExpressionFactory(ValueExpressionFactory.ID);
            return factory.buildExpression(this, wordParser, word, getQueryBNF(), null, false);
        }

        if (word.indexOf(DOT) == -1) {
            return new IdentificationVariable(this, word);
        }

        return super.buildEncapsulatedExpression(wordParser, word);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getEncapsulatedExpressionQueryBNFId() {
        return InternalCountBNF.ID;
    }
}