/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.configuration.internal;

import java.util.Collections;
import java.util.List;
import java.util.Properties;

import org.xwiki.configuration.ConfigurationSource;

/**
 * Base class to use to implement {@link ConfigurationSource}.
 * 
 * @version $Id$
 * @since 3.5M1
 */
public abstract class AbstractConfigurationSource implements ConfigurationSource
{
    /**
     * @param valueClass the class of the property
     * @param <T> the type of the property
     * @return the default value of a property for the provided class
     */
    protected <T> T getDefault(Class<T> valueClass)
    {
        T result;

        if (List.class.getName().equals(valueClass.getName())) {
            result = (T) Collections.emptyList();
        } else if (Properties.class.getName().equals(valueClass.getName())) {
            result = (T) new Properties();
        } else {
            result = null;
        }

        return result;
    }
}

/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.configuration.internal;

import java.util.Collections;
import java.util.List;
import java.util.Properties;

import org.xwiki.configuration.ConfigurationSource;

/**
 * Base class to use to implement {@link ConfigurationSource}.
 * 
 * @version $Id$
 * @since 3.5M1
 */
public abstract class AbstractConfigurationSource implements ConfigurationSource
{
    /**
     * @param valueClass the class of the property
     * @param <T> the type of the property
     * @return the default value of a property for the provided class
     */
    protected <T> T getDefault(Class<T> valueClass)
    {
        T result = null;

        if (valueClass != null) {
            if (List.class.getName().equals(valueClass.getName())) {
                result = (T) Collections.emptyList();
            } else if (Properties.class.getName().equals(valueClass.getName())) {
                result = (T) new Properties();
            }
        }

        return result;
    }
}

Add a ConfigurationSource Provider which provide an default configuration when no ConfigurationSource can be found Add support for null property class (even if it does not make much sense but better be as strong as possible)