/*
 * 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.
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package org.apache.commons.configuration2.builder.combined;

import java.util.Collection;
import java.util.LinkedList;
import java.util.Map;

import org.apache.commons.configuration2.CombinedConfiguration;
import org.apache.commons.configuration2.Configuration;
import org.apache.commons.configuration2.HierarchicalConfiguration;
import org.apache.commons.configuration2.XMLConfiguration;
import org.apache.commons.configuration2.builder.BuilderParameters;
import org.apache.commons.configuration2.builder.ConfigurationBuilder;
import org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder;
import org.apache.commons.configuration2.ex.ConfigurationException;
import org.apache.commons.configuration2.reloading.CombinedReloadingController;
import org.apache.commons.configuration2.reloading.ReloadingController;
import org.apache.commons.configuration2.reloading.ReloadingControllerSupport;

 An extension of CombinedConfigurationBuilder which also supports reloading operations. 

This class differs from its super class in the following aspects:


A ReloadingController is created which manages all child configuration builders supporting reloading operations.
If no ConfigurationBuilder is provided for the definition configuration, a builder with reloading support is created.


This class can be used exactly as its super class for creating combined
configurations from multiple configuration sources. In addition, the combined
reloading controller managed by an instance can be used to react on changes
in one of these configuration sources or in the definition configuration.

Since:
2.0/**
 * <p>
 * An extension of {@code CombinedConfigurationBuilder} which also supports
 * reloading operations.
 * </p>
 * <p>
 * This class differs from its super class in the following aspects:
 * </p>
 * <ul>
 * <li>A {@link ReloadingController} is created which manages all child
 * configuration builders supporting reloading operations.</li>
 * <li>If no {@code ConfigurationBuilder} is provided for the definition
 * configuration, a builder with reloading support is created.</li>
 * </ul>
 * <p>
 * This class can be used exactly as its super class for creating combined
 * configurations from multiple configuration sources. In addition, the combined
 * reloading controller managed by an instance can be used to react on changes
 * in one of these configuration sources or in the definition configuration.
 * </p>
 *
 * @since 2.0
 */
public class ReloadingCombinedConfigurationBuilder extends
        CombinedConfigurationBuilder implements ReloadingControllerSupport
{
    
The reloading controller used by this builder. /** The reloading controller used by this builder. */
    private ReloadingController reloadingController;

    
Creates a new instance of ReloadingCombinedConfigurationBuilder. No parameters are set. /**
     * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder}.
     * No parameters are set.
     */
    public ReloadingCombinedConfigurationBuilder()
    {
        super();
    }

    
Creates a new instance of ReloadingCombinedConfigurationBuilder and sets the specified initialization parameters and the allowFailOnInit flag.
Params:
params – a map with initialization parameters
allowFailOnInit – the allowFailOnInit flag/**
     * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder}
     * and sets the specified initialization parameters and the
     * <em>allowFailOnInit</em> flag.
     *
     * @param params a map with initialization parameters
     * @param allowFailOnInit the <em>allowFailOnInit</em> flag
     */
    public ReloadingCombinedConfigurationBuilder(final Map<String, Object> params,
            final boolean allowFailOnInit)
    {
        super(params, allowFailOnInit);
    }

    
Creates a new instance of ReloadingCombinedConfigurationBuilder and sets the specified initialization parameters. 
Params:
params – a map with initialization parameters/**
     * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder}
     * and sets the specified initialization parameters.
     *
     * @param params a map with initialization parameters
     */
    public ReloadingCombinedConfigurationBuilder(final Map<String, Object> params)
    {
        super(params);
    }

    
{@inheritDoc} This method is overridden to adapt the return type.
/**
     * {@inheritDoc} This method is overridden to adapt the return type.
     */
    @Override
    public ReloadingCombinedConfigurationBuilder configure(final BuilderParameters... params)
    {
        super.configure(params);
        return this;
    }

    
{@inheritDoc} This implementation returns a CombinedReloadingController which contains sub controllers for all child configuration sources with reloading support. If the definition builder supports reloading, its controller is contained, too. Note that the combined reloading controller is initialized when the result configuration is created (i.e. when calling getConfiguration() for the first time). So this method does not return a meaningful result before. /**
     * {@inheritDoc} This implementation returns a
     * {@link CombinedReloadingController} which contains sub controllers for
     * all child configuration sources with reloading support. If the definition
     * builder supports reloading, its controller is contained, too. Note that
     * the combined reloading controller is initialized when the result
     * configuration is created (i.e. when calling {@code getConfiguration()}
     * for the first time). So this method does not return a meaningful result
     * before.
     */
    @Override
    public synchronized ReloadingController getReloadingController()
    {
        return reloadingController;
    }

    
{@inheritDoc} This implementation makes sure that the reloading state of the managed reloading controller is reset. Note that this has to be done here and not in initResultInstance(CombinedConfiguration) because it must be outside of a synchronized block; otherwise, a dead-lock situation can occur. /**
     * {@inheritDoc} This implementation makes sure that the reloading state of
     * the managed reloading controller is reset. Note that this has to be done
     * here and not in {@link #initResultInstance(CombinedConfiguration)}
     * because it must be outside of a synchronized block; otherwise, a
     * dead-lock situation can occur.
     */
    @Override
    public CombinedConfiguration getConfiguration() throws ConfigurationException
    {
        final CombinedConfiguration result = super.getConfiguration();
        reloadingController.resetReloadingState();
        return result;
    }

    
{@inheritDoc} This implementation creates a builder for XML
configurations with reloading support.
/**
     * {@inheritDoc} This implementation creates a builder for XML
     * configurations with reloading support.
     */
    @Override
    protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>> createXMLDefinitionBuilder(
            final BuilderParameters builderParams)
    {
        return new ReloadingFileBasedConfigurationBuilder<>(
                XMLConfiguration.class).configure(builderParams);
    }

    
{@inheritDoc} This implementation first calls the super method to actually initialize the result configuration. Then it creates the CombinedReloadingController for all child configuration sources with reloading support. /**
     * {@inheritDoc} This implementation first calls the super method to
     * actually initialize the result configuration. Then it creates the
     * {@link CombinedReloadingController} for all child configuration sources
     * with reloading support.
     */
    @Override
    protected void initResultInstance(final CombinedConfiguration result)
            throws ConfigurationException
    {
        super.initResultInstance(result);
        if (reloadingController == null)
        {
            reloadingController = createReloadingController();
        }
    }

    
Creates the ReloadingController for this builder. This method is called after the result configuration has been created and initialized. It is called from a synchronized block. This implementation creates a CombinedReloadingController. 
Throws:
ConfigurationException – if an error occurs
Returns:
the ReloadingController for this builder/**
     * Creates the {@code ReloadingController} for this builder. This method is
     * called after the result configuration has been created and initialized.
     * It is called from a synchronized block. This implementation creates a
     * {@link CombinedReloadingController}.
     *
     * @return the {@code ReloadingController} for this builder
     * @throws ConfigurationException if an error occurs
     */
    protected ReloadingController createReloadingController()
            throws ConfigurationException
    {
        final Collection<ReloadingController> subControllers =
                new LinkedList<>();
        final ConfigurationBuilder<? extends HierarchicalConfiguration<?>> defBuilder =
                getDefinitionBuilder();
        obtainReloadingController(subControllers, defBuilder);

        for (final ConfigurationBuilder<? extends Configuration> b : getChildBuilders())
        {
            obtainReloadingController(subControllers, b);
        }

        final CombinedReloadingController ctrl =
                new CombinedReloadingController(subControllers);
        ctrl.resetInitialReloadingState();
        return ctrl;
    }

    
Checks whether the passed in builder object supports reloading. If yes,
its reloading controller is obtained and added to the given list.
Params:
subControllers – the list with sub controllers
builder – the builder object to be checked/**
     * Checks whether the passed in builder object supports reloading. If yes,
     * its reloading controller is obtained and added to the given list.
     *
     * @param subControllers the list with sub controllers
     * @param builder the builder object to be checked
     */
    public static void obtainReloadingController(
            final Collection<ReloadingController> subControllers, final Object builder)
    {
        if (builder instanceof ReloadingControllerSupport)
        {
            subControllers.add(((ReloadingControllerSupport) builder)
                    .getReloadingController());
        }
    }
}