CombinedBuilderParametersImpl.java

/*
 * 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.configuration2.builder.combined;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;

import org.apache.commons.configuration2.ConfigurationUtils;
import org.apache.commons.configuration2.HierarchicalConfiguration;
import org.apache.commons.configuration2.builder.BasicBuilderParameters;
import org.apache.commons.configuration2.builder.BuilderParameters;
import org.apache.commons.configuration2.builder.ConfigurationBuilder;
import org.apache.commons.configuration2.builder.DefaultParametersHandler;
import org.apache.commons.configuration2.builder.DefaultParametersManager;

/**
 * <p>
 * A specialized parameters object for a {@link CombinedConfigurationBuilder}.
 * </p>
 * <p>
 * This class defines methods for setting properties for customizing a builder for combined configurations. Note that
 * some of these properties can also be set in the configuration definition file. If this is the case, the settings in
 * the definition file override the content of this object.
 * </p>
 * <p>
 * This class is not thread-safe. It is intended that an instance is constructed and initialized by a single thread
 * during configuration of a {@code ConfigurationBuilder}.
 * </p>
 *
 * @since 2.0
 */
public class CombinedBuilderParametersImpl extends BasicBuilderParameters implements CombinedBuilderProperties<CombinedBuilderParametersImpl> {
    /** Constant for the key in the parameters map used by this class. */
    private static final String PARAM_KEY = RESERVED_PARAMETER_PREFIX + CombinedBuilderParametersImpl.class.getName();

    /**
     * Looks up an instance of this class in the specified parameters map. This is equivalent to
     * {@code fromParameters(params, false);}
     *
     * @param params the map with parameters (must not be <strong>null</strong>
     * @return the instance obtained from the map or <strong>null</strong>
     * @throws NullPointerException if the map is <strong>null</strong>
     */
    public static CombinedBuilderParametersImpl fromParameters(final Map<String, ?> params) {
        return fromParameters(params, false);
    }

    /**
     * Looks up an instance of this class in the specified parameters map and optionally creates a new one if none is found.
     * This method can be used to obtain an instance of this class which has been stored in a parameters map. It is
     * compatible with the {@code getParameters()} method.
     *
     * @param params the map with parameters (must not be <strong>null</strong>
     * @param createIfMissing determines the behavior if no instance is found in the map; if <strong>true</strong>, a new instance
     *        with default settings is created; if <strong>false</strong>, <strong>null</strong> is returned
     * @return the instance obtained from the map or <strong>null</strong>
     * @throws NullPointerException if the map is <strong>null</strong>
     */
    public static CombinedBuilderParametersImpl fromParameters(final Map<String, ?> params, final boolean createIfMissing) {
        CombinedBuilderParametersImpl result = (CombinedBuilderParametersImpl) params.get(PARAM_KEY);
        if (result == null && createIfMissing) {
            result = new CombinedBuilderParametersImpl();
        }
        return result;
    }

    /** The definition configuration builder. */
    private ConfigurationBuilder<? extends HierarchicalConfiguration<?>> definitionBuilder;

    /** A parameters object for the definition configuration builder. */
    private BuilderParameters definitionBuilderParameters;

    /** A map with registered configuration builder providers. */
    private final Map<String, ConfigurationBuilderProvider> providers;

    /** A list with default parameters for child configuration sources. */
    private final Collection<BuilderParameters> childParameters;

    /** The manager for default handlers. */
    private DefaultParametersManager childDefaultParametersManager;

    /** The base path for configuration sources to be loaded. */
    private String basePath;

    /** A flag whether settings should be inherited by child builders. */
    private boolean inheritSettings;

    /**
     * Creates a new instance of {@code CombinedBuilderParametersImpl}.
     */
    public CombinedBuilderParametersImpl() {
        providers = new HashMap<>();
        childParameters = new LinkedList<>();
        inheritSettings = true;
    }

    /**
     * {@inheritDoc} This implementation also clones the parameters object for the definition builder if possible.
     */
    @Override
    public CombinedBuilderParametersImpl clone() {
        final CombinedBuilderParametersImpl copy = (CombinedBuilderParametersImpl) super.clone();
        copy.setDefinitionBuilderParameters((BuilderParameters) ConfigurationUtils.cloneIfPossible(getDefinitionBuilderParameters()));
        return copy;
    }

    /**
     * Gets the base path for relative names of configuration sources. Result may be <strong>null</strong> if no base path has been
     * set.
     *
     * @return the base path for resolving relative file names
     */
    public String getBasePath() {
        return basePath;
    }

    /**
     * Gets the {@code DefaultParametersManager} object for initializing parameter objects for child configuration
     * sources. This method never returns <strong>null</strong>. If no manager was set, a new instance is created right now.
     *
     * @return the {@code DefaultParametersManager} for child configuration sources
     */
    public DefaultParametersManager getChildDefaultParametersManager() {
        if (childDefaultParametersManager == null) {
            childDefaultParametersManager = new DefaultParametersManager();
        }
        return childDefaultParametersManager;
    }

    /**
     * Gets a collection with default parameter objects for child configuration sources. This collection contains the
     * same objects (in the same order) that were passed to {@code addChildParameters()}. The returned collection is a
     * defensive copy; it can be modified, but this has no effect on the parameters stored in this object.
     *
     * @return a map with default parameters for child sources
     */
    public Collection<? extends BuilderParameters> getDefaultChildParameters() {
        return new ArrayList<>(childParameters);
    }

    /**
     * Gets the {@code ConfigurationBuilder} object for obtaining the definition configuration.
     *
     * @return the definition {@code ConfigurationBuilder}
     */
    public ConfigurationBuilder<? extends HierarchicalConfiguration<?>> getDefinitionBuilder() {
        return definitionBuilder;
    }

    /**
     * Gets the parameters object for the definition configuration builder if present.
     *
     * @return the parameters object for the definition configuration builder or <strong>null</strong>
     */
    public BuilderParameters getDefinitionBuilderParameters() {
        return definitionBuilderParameters;
    }

    /**
     * {@inheritDoc} This implementation returns a map which contains this object itself under a specific key. The static
     * {@code fromParameters()} method can be used to extract an instance from a parameters map.
     */
    @Override
    public Map<String, Object> getParameters() {
        final Map<String, Object> params = super.getParameters();
        params.put(PARAM_KEY, this);
        return params;
    }

    /**
     * Gets an (unmodifiable) map with the currently registered {@code ConfigurationBuilderProvider} objects.
     *
     * @return the map with {@code ConfigurationBuilderProvider} objects (the keys are the tag names)
     */
    public Map<String, ConfigurationBuilderProvider> getProviders() {
        return Collections.unmodifiableMap(providers);
    }

    /**
     * {@inheritDoc} This implementation additionally copies some properties defined by this class.
     */
    @Override
    public void inheritFrom(final Map<String, ?> source) {
        super.inheritFrom(source);

        final CombinedBuilderParametersImpl srcParams = fromParameters(source);
        if (srcParams != null) {
            setChildDefaultParametersManager(srcParams.getChildDefaultParametersManager());
            setInheritSettings(srcParams.isInheritSettings());
        }
    }

    /**
     * Returns the current value of the flag that controls whether the settings of the parent combined configuration builder
     * should be inherited by its child configurations.
     *
     * @return the flag whether settings should be inherited by child configurations
     */
    public boolean isInheritSettings() {
        return inheritSettings;
    }

    /**
     * Returns the {@code ConfigurationBuilderProvider} which is registered for the specified tag name or <strong>null</strong> if
     * there is no registration for this tag.
     *
     * @param tagName the tag name
     * @return the provider registered for this tag or <strong>null</strong>
     */
    public ConfigurationBuilderProvider providerForTag(final String tagName) {
        return providers.get(tagName);
    }

    /**
     * {@inheritDoc} This implementation registers the passed in handler at an internal {@link DefaultParametersManager}
     * instance. If none was set, a new instance is created now.
     */
    @Override
    public <D> CombinedBuilderParametersImpl registerChildDefaultsHandler(final Class<D> paramClass, final DefaultParametersHandler<? super D> handler) {
        getChildDefaultParametersManager().registerDefaultsHandler(paramClass, handler);
        return this;
    }

    /**
     * {@inheritDoc} This implementation registers the passed in handler at an internal {@link DefaultParametersManager}
     * instance. If none was set, a new instance is created now.
     */
    @Override
    public <D> CombinedBuilderParametersImpl registerChildDefaultsHandler(final Class<D> paramClass, final DefaultParametersHandler<? super D> handler,
        final Class<?> startClass) {
        getChildDefaultParametersManager().registerDefaultsHandler(paramClass, handler, startClass);
        return this;
    }

    /**
     * Registers all {@code ConfigurationBuilderProvider}s in the given parameters object which have not yet been
     * registered. This method works like the method with the same name, but the map with providers is obtained from the
     * passed in parameters object.
     *
     * @param params the parameters object from which to copy providers(must not be <strong>null</strong>)
     * @return a reference to this object for method chaining
     * @throws IllegalArgumentException if the source parameters object is <strong>null</strong>
     */
    public CombinedBuilderParametersImpl registerMissingProviders(final CombinedBuilderParametersImpl params) {
        if (params == null) {
            throw new IllegalArgumentException("Source parameters must not be null!");
        }
        return registerMissingProviders(params.getProviders());
    }

    /**
     * Registers all {@code ConfigurationBuilderProvider}s in the given map to this object which have not yet been
     * registered. This method is mainly used for internal purposes: a {@code CombinedConfigurationBuilder} takes the
     * providers contained in a parameters object and adds all standard providers. This way it is possible to override a
     * standard provider by registering a provider object for the same tag name at the parameters object.
     *
     * @param providers a map with tag names and corresponding providers (must not be <strong>null</strong> or contain <strong>null</strong>
     *        entries)
     * @return a reference to this object for method chaining
     * @throws IllegalArgumentException if the map with providers is <strong>null</strong> or contains <strong>null</strong> entries
     */
    public CombinedBuilderParametersImpl registerMissingProviders(final Map<String, ConfigurationBuilderProvider> providers) {
        if (providers == null) {
            throw new IllegalArgumentException("Map with providers must not be null!");
        }
        providers.forEach((k, v) -> {
            if (!this.providers.containsKey(k)) {
                registerProvider(k, v);
            }
        });
        return this;
    }

    /**
     * Registers the given {@code ConfigurationBuilderProvider} for the specified tag name. This means that whenever this
     * tag is encountered in a configuration definition file, the corresponding builder provider is invoked.
     *
     * @param tagName the name of the tag (must not be <strong>null</strong>)
     * @param provider the {@code ConfigurationBuilderProvider} (must not be <strong>null</strong>)
     * @return a reference to this object for method chaining
     * @throws IllegalArgumentException if a required parameter is missing
     */
    @Override
    public CombinedBuilderParametersImpl registerProvider(final String tagName, final ConfigurationBuilderProvider provider) {
        if (tagName == null) {
            throw new IllegalArgumentException("Tag name must not be null!");
        }
        if (provider == null) {
            throw new IllegalArgumentException("Provider must not be null!");
        }

        providers.put(tagName, provider);
        return this;
    }

    /**
     * Sets the base path for this combined configuration builder. Normally it it not necessary to set the base path
     * explicitly. Per default, relative file names of configuration sources are resolved based on the location of the
     * definition file. If this is not desired or if the definition configuration is loaded by a different means, the base
     * path for relative file names can be specified using this method.
     *
     * @param path the base path for resolving relative file names
     * @return a reference to this object for method chaining
     */
    @Override
    public CombinedBuilderParametersImpl setBasePath(final String path) {
        basePath = path;
        return this;
    }

    /**
     * {@inheritDoc} This implementation stores the passed in manager object. An already existing manager object (either
     * explicitly set or created on demand) is overridden. This also removes all default handlers registered before!
     */
    @Override
    public CombinedBuilderParametersImpl setChildDefaultParametersManager(final DefaultParametersManager manager) {
        childDefaultParametersManager = manager;
        return this;
    }

    /**
     * Sets the {@code ConfigurationBuilder} for the definition configuration. This is the configuration which contains the
     * configuration sources that form the combined configuration.
     *
     * @param builder the definition {@code ConfigurationBuilder}
     * @return a reference to this object for method chaining
     */
    @Override
    public CombinedBuilderParametersImpl setDefinitionBuilder(final ConfigurationBuilder<? extends HierarchicalConfiguration<?>> builder) {
        definitionBuilder = builder;
        return this;
    }

    /**
     * Sets the parameters object for the definition configuration builder. This property is evaluated only if the
     * definition configuration builder is not set explicitly (using the {@link #setDefinitionBuilder(ConfigurationBuilder)}
     * method). In this case, a builder for an XML configuration is created and configured with this parameters object.
     *
     * @param params the parameters object for the definition configuration builder
     * @return a reference to this object for method chaining
     */
    @Override
    public CombinedBuilderParametersImpl setDefinitionBuilderParameters(final BuilderParameters params) {
        definitionBuilderParameters = params;
        return this;
    }

    @Override
    public CombinedBuilderParametersImpl setInheritSettings(final boolean inheritSettings) {
        this.inheritSettings = inheritSettings;
        return this;
    }
}