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Tools to assist in the reading of configuration/preferences files in various formats
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/*
 * 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.
 */

package org.apache.commons.configuration;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.commons.collections.map.LinkedMap;

/**
 * Basic configuration class. Stores the configuration data but does not
 * provide any load or save functions. If you want to load your Configuration
 * from a file use PropertiesConfiguration or XmlConfiguration.
 *
 * This class extends normal Java properties by adding the possibility
 * to use the same key many times concatenating the value strings
 * instead of overwriting them.
 *
 * @author Stefano Mazzocchi
 * @author Jon S. Stevens
 * @author Dave Bryson
 * @author Geir Magnusson Jr.
 * @author Leon Messerschmidt
 * @author Kent Johnson
 * @author Daniel Rall
 * @author Ilkka Priha
 * @author Jason van Zyl
 * @author Martin Poeschl
 * @author Henning P. Schmiedehausen
 * @author Konstantin Shaposhnikov
 * @author Oliver Heger
 * @version $Id: BaseConfiguration.java 806862 2009-08-22 15:13:31Z oheger $
 */
public class BaseConfiguration extends AbstractConfiguration implements Cloneable
{
    /** stores the configuration key-value pairs */
    private Map store = new LinkedMap();

    /**
     * Adds a key/value pair to the map.  This routine does no magic morphing.
     * It ensures the keylist is maintained
     *
     * @param key key to use for mapping
     * @param value object to store
     */
    protected void addPropertyDirect(String key, Object value)
    {
        Object previousValue = getProperty(key);

        if (previousValue == null)
        {
            store.put(key, value);
        }
        else if (previousValue instanceof List)
        {
            // the value is added to the existing list
            ((List) previousValue).add(value);
        }
        else
        {
            // the previous value is replaced by a list containing the previous value and the new value
            List list = new ArrayList();
            list.add(previousValue);
            list.add(value);

            store.put(key, list);
        }
    }

    /**
     * Read property from underlying map.
     *
     * @param key key to use for mapping
     *
     * @return object associated with the given configuration key.
     */
    public Object getProperty(String key)
    {
        return store.get(key);
    }

    /**
     * Check if the configuration is empty
     *
     * @return true if Configuration is empty,
     * false otherwise.
     */
    public boolean isEmpty()
    {
        return store.isEmpty();
    }

    /**
     * check if the configuration contains the key
     *
     * @param key the configuration key
     *
     * @return true if Configuration contain given key,
     * false otherwise.
     */
    public boolean containsKey(String key)
    {
        return store.containsKey(key);
    }

    /**
     * Clear a property in the configuration.
     *
     * @param key the key to remove along with corresponding value.
     */
    protected void clearPropertyDirect(String key)
    {
        if (containsKey(key))
        {
            store.remove(key);
        }
    }

    public void clear()
    {
        fireEvent(EVENT_CLEAR, null, null, true);
        store.clear();
        fireEvent(EVENT_CLEAR, null, null, false);
    }

    /**
     * Get the list of the keys contained in the configuration
     * repository.
     *
     * @return An Iterator.
     */
    public Iterator getKeys()
    {
        return store.keySet().iterator();
    }

    /**
     * Creates a copy of this object. This implementation will create a deep
     * clone, i.e. the map that stores the properties is cloned, too. So changes
     * performed at the copy won't affect the original and vice versa.
     *
     * @return the copy
     * @since 1.3
     */
    public Object clone()
    {
        try
        {
            BaseConfiguration copy = (BaseConfiguration) super.clone();
            copy.store = (Map) ConfigurationUtils.clone(store);

            // Handle collections in the map; they have to be cloned, too
            for (Iterator it = store.entrySet().iterator(); it.hasNext();)
            {
                Map.Entry e = (Map.Entry) it.next();
                if (e.getValue() instanceof Collection)
                {
                    copy.store.put(e.getKey(), new ArrayList((Collection) e
                            .getValue()));
                }
            }

            return copy;
        }
        catch (CloneNotSupportedException cex)
        {
            // should not happen
            throw new ConfigurationRuntimeException(cex);
        }
    }
}