BasicBuilderParameters.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;

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

import org.apache.commons.configuration2.ConfigurationDecoder;
import org.apache.commons.configuration2.beanutils.BeanHelper;
import org.apache.commons.configuration2.convert.ConversionHandler;
import org.apache.commons.configuration2.convert.ListDelimiterHandler;
import org.apache.commons.configuration2.interpol.ConfigurationInterpolator;
import org.apache.commons.configuration2.interpol.InterpolatorSpecification;
import org.apache.commons.configuration2.interpol.Lookup;
import org.apache.commons.configuration2.io.ConfigurationLogger;
import org.apache.commons.configuration2.sync.Synchronizer;

/**
 * <p>
 * An implementation of {@code BuilderParameters} which handles the parameters of a {@link ConfigurationBuilder} common
 * to all concrete {@code Configuration} implementations.
 * </p>
 * <p>
 * This class provides methods for setting standard properties supported by the {@code AbstractConfiguration} base
 * class. A fluent interface can be used to set property values.
 * </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 BasicBuilderParameters implements Cloneable, BuilderParameters, BasicBuilderProperties<BasicBuilderParameters> {
    /** The key of the <em>throwExceptionOnMissing</em> property. */
    private static final String PROP_THROW_EXCEPTION_ON_MISSING = "throwExceptionOnMissing";

    /** The key of the <em>listDelimiterHandler</em> property. */
    private static final String PROP_LIST_DELIMITER_HANDLER = "listDelimiterHandler";

    /** The key of the <em>logger</em> property. */
    private static final String PROP_LOGGER = "logger";

    /** The key for the <em>interpolator</em> property. */
    private static final String PROP_INTERPOLATOR = "interpolator";

    /** The key for the <em>prefixLookups</em> property. */
    private static final String PROP_PREFIX_LOOKUPS = "prefixLookups";

    /** The key for the <em>defaultLookups</em> property. */
    private static final String PROP_DEFAULT_LOOKUPS = "defaultLookups";

    /** The key for the <em>parentInterpolator</em> property. */
    private static final String PROP_PARENT_INTERPOLATOR = "parentInterpolator";

    /** The key for the <em>synchronizer</em> property. */
    private static final String PROP_SYNCHRONIZER = "synchronizer";

    /** The key for the <em>conversionHandler</em> property. */
    private static final String PROP_CONVERSION_HANDLER = "conversionHandler";

    /** The key for the <em>configurationDecoder</em> property. */
    private static final String PROP_CONFIGURATION_DECODER = "configurationDecoder";

    /** The key for the {@code BeanHelper}. */
    private static final String PROP_BEAN_HELPER = RESERVED_PARAMETER_PREFIX + "BeanHelper";

    /**
     * Checks whether a map with parameters is present. Throws an exception if not.
     *
     * @param params the map with parameters to check
     * @throws IllegalArgumentException if the map is <strong>null</strong>
     */
    private static void checkParameters(final Map<String, Object> params) {
        if (params == null) {
            throw new IllegalArgumentException("Parameters map must not be null!");
        }
    }

    /**
     * Creates defensive copies for collection structures when constructing the map with parameters. It should not be
     * possible to modify this object's internal state when having access to the parameters map.
     *
     * @param params the map with parameters to be passed to the caller
     */
    private static void createDefensiveCopies(final HashMap<String, Object> params) {
        final Map<String, ? extends Lookup> prefixLookups = fetchPrefixLookups(params);
        if (prefixLookups != null) {
            params.put(PROP_PREFIX_LOOKUPS, new HashMap<>(prefixLookups));
        }
        final Collection<? extends Lookup> defLookups = fetchDefaultLookups(params);
        if (defLookups != null) {
            params.put(PROP_DEFAULT_LOOKUPS, new ArrayList<>(defLookups));
        }
    }

    /**
     * Tests whether the passed in map with parameters contains a valid collection with default lookups. This method works
     * like {@link #fetchAndCheckPrefixLookups(Map)}, but tests the default lookups collection.
     *
     * @param params the map with parameters
     * @return the collection with default lookups (may be <strong>null</strong>)
     * @throws IllegalArgumentException if invalid data is found
     */
    private static Collection<? extends Lookup> fetchAndCheckDefaultLookups(final Map<String, Object> params) {
        final Collection<?> col = fetchParameter(params, PROP_DEFAULT_LOOKUPS, Collection.class);
        if (col == null) {
            return null;
        }

        if (col.stream().noneMatch(Lookup.class::isInstance)) {
            throw new IllegalArgumentException("Collection with default lookups contains invalid data: " + col);
        }
        return fetchDefaultLookups(params);
    }

    /**
     * Tests whether the passed in map with parameters contains a map with prefix lookups. This method is used if the
     * parameters map is from an insecure source and we cannot be sure that it contains valid data. Therefore, we have to
     * map that the key for the prefix lookups actually points to a map containing keys and values of expected data types.
     *
     * @param params the parameters map
     * @return the obtained map with prefix lookups
     * @throws IllegalArgumentException if the map contains invalid data
     */
    private static Map<String, ? extends Lookup> fetchAndCheckPrefixLookups(final Map<String, Object> params) {
        final Map<?, ?> prefixes = fetchParameter(params, PROP_PREFIX_LOOKUPS, Map.class);
        if (prefixes == null) {
            return null;
        }
        prefixes.forEach((k, v) -> {
            if (!(k instanceof String) || !(v instanceof Lookup)) {
                throw new IllegalArgumentException("Map with prefix lookups contains invalid data: " + prefixes);
            }
        });
        return fetchPrefixLookups(params);
    }

    /**
     * Obtains the {@code BeanHelper} object from the specified map with parameters. This method can be used to obtain an
     * instance from a parameters map that has been set via the {@code setBeanHelper()} method. If no such instance is
     * found, result is <strong>null</strong>.
     *
     * @param params the map with parameters (must not be <strong>null</strong>)
     * @return the {@code BeanHelper} stored in this map or <strong>null</strong>
     * @throws IllegalArgumentException if the map is <strong>null</strong>
     */
    public static BeanHelper fetchBeanHelper(final Map<String, Object> params) {
        checkParameters(params);
        return (BeanHelper) params.get(PROP_BEAN_HELPER);
    }

    /**
     * Obtains the collection with default lookups from the parameters map.
     *
     * @param params the map with parameters
     * @return the collection with default lookups (may be <strong>null</strong>)
     */
    private static Collection<? extends Lookup> fetchDefaultLookups(final Map<String, Object> params) {
        // This is safe to cast because we either have full control over the map
        // and thus know the types of the contained values or have checked
        // the content before
        @SuppressWarnings("unchecked")
        final Collection<? extends Lookup> defLookups = (Collection<? extends Lookup>) params.get(PROP_DEFAULT_LOOKUPS);
        return defLookups;
    }

    /**
     * Obtains a specification for a {@link ConfigurationInterpolator} from the specified map with parameters. All
     * properties related to interpolation are evaluated and added to the specification object.
     *
     * @param params the map with parameters (must not be <strong>null</strong>)
     * @return an {@code InterpolatorSpecification} object constructed with data from the map
     * @throws IllegalArgumentException if the map is <strong>null</strong> or contains invalid data
     */
    public static InterpolatorSpecification fetchInterpolatorSpecification(final Map<String, Object> params) {
        checkParameters(params);
        return new InterpolatorSpecification.Builder().withInterpolator(fetchParameter(params, PROP_INTERPOLATOR, ConfigurationInterpolator.class))
            .withParentInterpolator(fetchParameter(params, PROP_PARENT_INTERPOLATOR, ConfigurationInterpolator.class))
            .withPrefixLookups(fetchAndCheckPrefixLookups(params)).withDefaultLookups(fetchAndCheckDefaultLookups(params)).create();
    }

    /**
     * Obtains a parameter from a map and performs a type check.
     *
     * @param params the map with parameters
     * @param key the key of the parameter
     * @param expClass the expected class of the parameter value
     * @param <T> the parameter type
     * @return the value of the parameter in the correct data type
     * @throws IllegalArgumentException if the parameter is not of the expected type
     */
    private static <T> T fetchParameter(final Map<String, Object> params, final String key, final Class<T> expClass) {
        final Object value = params.get(key);
        if (value == null) {
            return null;
        }
        if (!expClass.isInstance(value)) {
            throw new IllegalArgumentException(String.format("Parameter %s is not of type %s!", key, expClass.getSimpleName()));
        }
        return expClass.cast(value);
    }

    /**
     * Obtains the map with prefix lookups from the parameters map.
     *
     * @param params the map with parameters
     * @return the map with prefix lookups (may be <strong>null</strong>)
     */
    private static Map<String, ? extends Lookup> fetchPrefixLookups(final Map<String, Object> params) {
        // This is safe to cast because we either have full control over the map
        // and thus know the types of the contained values or have checked
        // the content before
        @SuppressWarnings("unchecked")
        final Map<String, ? extends Lookup> prefixLookups = (Map<String, ? extends Lookup>) params.get(PROP_PREFIX_LOOKUPS);
        return prefixLookups;
    }

    /** The map for storing the current property values. */
    private Map<String, Object> properties;

    /**
     * Creates a new instance of {@code BasicBuilderParameters}.
     */
    public BasicBuilderParameters() {
        properties = new HashMap<>();
    }

    /**
     * Clones this object. This is useful because multiple builder instances may use a similar set of parameters. However,
     * single instances of parameter objects must not assigned to multiple builders. Therefore, cloning a parameters object
     * provides a solution for this use case. This method creates a new parameters object with the same content as this one.
     * The internal map storing the parameter values is cloned, too, also collection structures contained in this map.
     * However, no a full deep clone operation is performed. Objects like a {@code ConfigurationInterpolator} or
     * {@code Lookup}s are shared between this and the newly created instance.
     *
     * @return a clone of this object
     */
    @Override
    public BasicBuilderParameters clone() {
        try {
            final BasicBuilderParameters copy = (BasicBuilderParameters) super.clone();
            copy.properties = getParameters();
            return copy;
        } catch (final CloneNotSupportedException cnex) {
            // should not happen
            throw new AssertionError(cnex);
        }
    }

    /**
     * Copies a number of properties from the given map into this object. Properties are only copied if they are defined in
     * the source map.
     *
     * @param source the source map
     * @param keys the keys to be copied
     */
    protected void copyPropertiesFrom(final Map<String, ?> source, final String... keys) {
        for (final String key : keys) {
            final Object value = source.get(key);
            if (value != null) {
                storeProperty(key, value);
            }
        }
    }

    /**
     * Obtains the value of the specified property from the internal map. This method can be used by derived classes if a
     * specific property is to be accessed. If the given key is not found, result is <strong>null</strong>.
     *
     * @param key the key of the property in question
     * @return the value of the property with this key or <strong>null</strong>
     */
    protected Object fetchProperty(final String key) {
        return properties.get(key);
    }

    /**
     * {@inheritDoc} This implementation returns a copy of the internal parameters map with the values set so far.
     * Collection structures (for example for lookup objects) are stored as defensive copies, so the original data cannot be
     * modified.
     */
    @Override
    public Map<String, Object> getParameters() {
        final HashMap<String, Object> result = new HashMap<>(properties);
        if (result.containsKey(PROP_INTERPOLATOR)) {
            // A custom ConfigurationInterpolator overrides lookups
            result.remove(PROP_PREFIX_LOOKUPS);
            result.remove(PROP_DEFAULT_LOOKUPS);
            result.remove(PROP_PARENT_INTERPOLATOR);
        }

        createDefensiveCopies(result);
        return result;
    }

    /**
     * Inherits properties from the specified map. This can be used for instance to reuse parameters from one builder in
     * another builder - also in parent-child relations in which a parent builder creates child builders. The purpose of
     * this method is to let a concrete implementation decide which properties can be inherited. Because parameters are
     * basically organized as a map it would be possible to simply copy over all properties from the source object. However,
     * this is not appropriate in all cases. For instance, some properties - like a {@code ConfigurationInterpolator} - are
     * tightly connected to a configuration and cannot be reused in a different context. For other properties, for example a file
     * name, it does not make sense to copy it. Therefore, an implementation has to be explicit in the properties it wants
     * to take over.
     *
     * @param source the source properties to inherit from
     * @throws IllegalArgumentException if the source map is <strong>null</strong>
     */
    public void inheritFrom(final Map<String, ?> source) {
        if (source == null) {
            throw new IllegalArgumentException("Source properties must not be null!");
        }
        copyPropertiesFrom(source, PROP_BEAN_HELPER, PROP_CONFIGURATION_DECODER, PROP_CONVERSION_HANDLER, PROP_LIST_DELIMITER_HANDLER, PROP_LOGGER,
            PROP_SYNCHRONIZER, PROP_THROW_EXCEPTION_ON_MISSING);
    }

    /**
     * Merges this object with the given parameters object. This method adds all property values defined by the passed in
     * parameters object to the internal storage which are not already in. So properties already defined in this object take
     * precedence. Property names starting with the reserved parameter prefix are ignored.
     *
     * @param p the object whose properties should be merged (must not be <strong>null</strong>)
     * @throws IllegalArgumentException if the passed in object is <strong>null</strong>
     */
    public void merge(final BuilderParameters p) {
        if (p == null) {
            throw new IllegalArgumentException("Parameters to merge must not be null!");
        }
        p.getParameters().forEach((k, v) -> {
            if (!properties.containsKey(k) && !k.startsWith(RESERVED_PARAMETER_PREFIX)) {
                storeProperty(k, v);
            }
        });
    }

    /**
     * {@inheritDoc} This implementation stores the passed in {@code BeanHelper} object in the internal parameters map, but
     * uses a reserved key, so that it is not used for the initialization of properties of the managed configuration object.
     * The {@code fetchBeanHelper()} method can be used to obtain the {@code BeanHelper} instance from a parameters map.
     */
    @Override
    public BasicBuilderParameters setBeanHelper(final BeanHelper beanHelper) {
        return setProperty(PROP_BEAN_HELPER, beanHelper);
    }

    /**
     * {@inheritDoc} This implementation stores the passed in {@code ConfigurationDecoder} object in the internal parameters
     * map.
     */
    @Override
    public BasicBuilderParameters setConfigurationDecoder(final ConfigurationDecoder decoder) {
        return setProperty(PROP_CONFIGURATION_DECODER, decoder);
    }

    /**
     * {@inheritDoc} This implementation stores the passed in {@code ConversionHandler} object in the internal parameters
     * map.
     */
    @Override
    public BasicBuilderParameters setConversionHandler(final ConversionHandler handler) {
        return setProperty(PROP_CONVERSION_HANDLER, handler);
    }

    /**
     * {@inheritDoc} A defensive copy of the passed in collection is created. A <strong>null</strong> argument causes all default
     * lookups to be removed from the internal parameters map.
     */
    @Override
    public BasicBuilderParameters setDefaultLookups(final Collection<? extends Lookup> lookups) {
        if (lookups == null) {
            properties.remove(PROP_DEFAULT_LOOKUPS);
            return this;
        }
        return setProperty(PROP_DEFAULT_LOOKUPS, new ArrayList<>(lookups));
    }

    /**
     * {@inheritDoc} The passed in {@code ConfigurationInterpolator} is set without modifications.
     */
    @Override
    public BasicBuilderParameters setInterpolator(final ConfigurationInterpolator ci) {
        return setProperty(PROP_INTERPOLATOR, ci);
    }

    /**
     * Sets the value of the <em>listDelimiterHandler</em> property. This property defines the object responsible for
     * dealing with list delimiter and escaping characters. Note:
     * {@link org.apache.commons.configuration2.AbstractConfiguration AbstractConfiguration} does not allow setting this
     * property to <strong>null</strong>. If the default {@code ListDelimiterHandler} is to be used, do not call this method.
     *
     * @param handler the {@code ListDelimiterHandler}
     * @return a reference to this object for method chaining
     */
    @Override
    public BasicBuilderParameters setListDelimiterHandler(final ListDelimiterHandler handler) {
        return setProperty(PROP_LIST_DELIMITER_HANDLER, handler);
    }

    /**
     * Sets the <em>logger</em> property. With this property a concrete {@code Log} object can be set for the configuration.
     * Thus logging behavior can be controlled.
     *
     * @param log the {@code Log} for the configuration produced by this builder
     * @return a reference to this object for method chaining
     */
    @Override
    public BasicBuilderParameters setLogger(final ConfigurationLogger log) {
        return setProperty(PROP_LOGGER, log);
    }

    /**
     * {@inheritDoc} This implementation stores the passed in {@code ConfigurationInterpolator} object in the internal
     * parameters map.
     */
    @Override
    public BasicBuilderParameters setParentInterpolator(final ConfigurationInterpolator parent) {
        return setProperty(PROP_PARENT_INTERPOLATOR, parent);
    }

    /**
     * {@inheritDoc} A defensive copy of the passed in map is created. A <strong>null</strong> argument causes all prefix lookups to
     * be removed from the internal parameters map.
     */
    @Override
    public BasicBuilderParameters setPrefixLookups(final Map<String, ? extends Lookup> lookups) {
        if (lookups == null) {
            properties.remove(PROP_PREFIX_LOOKUPS);
            return this;
        }
        return setProperty(PROP_PREFIX_LOOKUPS, new HashMap<>(lookups));
    }

    /**
     * Helper method for setting a property value.
     *
     * @param key the key of the property
     * @param value the value of the property
     * @return a reference to this object
     */
    private BasicBuilderParameters setProperty(final String key, final Object value) {
        storeProperty(key, value);
        return this;
    }

    /**
     * {@inheritDoc} This implementation stores the passed in {@code Synchronizer} object in the internal parameters map.
     */
    @Override
    public BasicBuilderParameters setSynchronizer(final Synchronizer sync) {
        return setProperty(PROP_SYNCHRONIZER, sync);
    }

    /**
     * Sets the value of the <em>throwExceptionOnMissing</em> property. This property controls the configuration's behavior
     * if missing properties are queried: a value of <strong>true</strong> causes the configuration to throw an exception, for a value
     * of <strong>false</strong> it will return <strong>null</strong> values. (Note: Methods returning a primitive data type will always throw
     * an exception if the property is not defined.)
     *
     * @param b the value of the property
     * @return a reference to this object for method chaining
     */
    @Override
    public BasicBuilderParameters setThrowExceptionOnMissing(final boolean b) {
        return setProperty(PROP_THROW_EXCEPTION_ON_MISSING, Boolean.valueOf(b));
    }

    /**
     * Sets a property for this parameters object. Properties are stored in an internal map. With this method a new entry
     * can be added to this map. If the value is <strong>null</strong>, the key is removed from the internal map. This method can be
     * used by sub classes which also store properties in a map.
     *
     * @param key the key of the property
     * @param value the value of the property
     */
    protected void storeProperty(final String key, final Object value) {
        if (value == null) {
            properties.remove(key);
        } else {
            properties.put(key, value);
        }
    }
}