package org.apache.torque.generator.source;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/**
 * The base implementation of the source interface.
 *
 * @version $Id: SourceImpl.java 1839288 2018-08-27 09:48:33Z tv $
 */
public abstract class SourceImpl implements Source
{
    /**
     * The root element of the parsed source.
     */
    private transient SourceElement rootElement;

    /**
     * Reads the root element and the whole untransformed source tree.
     *
     * @return the root element, not null.
     *
     * @throws SourceException if the SourceElement cannot be created.
     */
    protected abstract SourceElement createRootElement() throws SourceException;

    @Override
    public synchronized SourceElement getRootElement()
            throws SourceException
    {
        if (rootElement == null)
        {
            rootElement = createRootElement();
        }
        return rootElement;
    }
}
