VirtualJPQLQueryBNF.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.parser;

import java.util.Random;

/**
 * This {@link JPQLQueryBNF} can be used as a virtual BNF, which can wrap another BNF or BNFs and
 * modify the default behavior.
 * <p>
 * The unique identifier for this BNF is automatically generated and can be retrieved with
 * {@link VirtualJPQLQueryBNF#getId()}.
 * <p>
 * Once this BNF is no longer needed, {@link #dispose()} needs to be called.
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
public final class VirtualJPQLQueryBNF extends JPQLQueryBNF {

    private static final Random r = new Random(System.currentTimeMillis());

    /**
     * Creates a new <code>VirtualJPQLQueryBNF</code>.
     *
     * @param jpqlGrammar The {@link JPQLGrammar} to integrate this virtual query BNF
     * @exception NullPointerException If the given {@link JPQLGrammar} is <code>null</code>
     */
    public VirtualJPQLQueryBNF(JPQLGrammar jpqlGrammar) {
        super(String.valueOf(r.nextLong()));
        initialize(jpqlGrammar);
    }

    /**
     * Disposes this "virtual" query BNF.
     */
    public void dispose() {
        getExpressionRegistry().unregisterBNF(this);
    }

    private void initialize(JPQLGrammar jpqlGrammar) {
        ExpressionRegistry expressionRegistry = jpqlGrammar.getExpressionRegistry();
        setExpressionRegistry(expressionRegistry);
        expressionRegistry.registerBNF(this);
    }

    /**
     * Registers a unique identifier that will be used to create the {@link Expression} representing
     * this BNF rule.
     *
     * @param expressionFactoryId The unique identifier that is responsible to create the
     * {@link Expression} for this BNF rule
     */
    public void registerFactory(String expressionFactoryId) {
        registerExpressionFactory(expressionFactoryId);
    }

    /**
     * Registers the unique identifier of the BNF rule as a child of this BNF rule.
     *
     * @param queryBNFId The unique identifier of the BNF rule
     * @exception NullPointerException The <code>queryBNFId</code> cannot be <code>null</code>
     */
    public void registerQueryBNF(String queryBNFId) {
        registerChild(queryBNFId);
    }
}