    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.configuration2.interpol;
    018
    019import java.util.ArrayList;
    020import java.util.Collection;
    021import java.util.Collections;
    022import java.util.HashMap;
    023import java.util.LinkedList;
    024import java.util.Map;
    025import java.util.function.Function;
    026
    027/**
    028 * <p>
    029 * A simple value class defining a {@link ConfigurationInterpolator}.
    030 * </p>
    031 * <p>
    032 * Objects of this class can be used for creating new {@code ConfigurationInterpolator} instances; they contain all
    033 * required properties. It is either possible to set a fully initialized {@code ConfigurationInterpolator} directly
    034 * which can be used as is. Alternatively, some or all properties of an instance to be newly created can be set. These
    035 * properties include
    036 * </p>
    037 * <ul>
    038 * <li>a map with {@code Lookup} objects associated with a specific prefix</li>
    039 * <li>a collection with default {@code Lookup} objects (without a prefix)</li>
    040 * <li>a parent {@code ConfigurationInterpolator}</li>
    041 * <li>a function used to convert interpolated values into strings</li>
    042 * </ul>
    043 * <p>
    044 * When setting up a configuration it is possible to define the {@code ConfigurationInterpolator} in terms of this
    045 * class. The configuration will then either use the {@code ConfigurationInterpolator} instance explicitly defined in
    046 * the {@code InterpolatorSpecification} instance or create a new one.
    047 * </p>
    048 * <p>
    049 * Instances are not created directly, but using the nested {@code Builder} class. They are then immutable.
    050 * </p>
    051 *
    052 * @since 2.0
    053 */
    054public final class InterpolatorSpecification {
    055    /**
    056     * <p>
    057     * A <em>builder</em> class for creating instances of {@code InterpolatorSpecification}.
    058     * </p>
    059     * <p>
    060     * This class provides a fluent API for defining the various properties of an {@code InterpolatorSpecification} object.
    061     * <em>Note:</em> This builder class is not thread-safe.
    062     * </p>
    063     */
    064    public static class Builder {
    065        /**
    066         * Helper method for checking a lookup. Throws an exception if the lookup is <b>null</b>.
    067         *
    068         * @param lookup the lookup to be checked
    069         * @throws IllegalArgumentException if the lookup is <b>null</b>
    070         */
    071        private static void checkLookup(final Lookup lookup) {
    072            if (lookup == null) {
    073                throw new IllegalArgumentException("Lookup must not be null!");
    074            }
    075        }
    076
    077        /** A map with prefix lookups. */
    078        private final Map<String, Lookup> prefixLookups;
    079
    080        /** A collection with default lookups. */
    081        private final Collection<Lookup> defLookups;
    082
    083        /** The {@code ConfigurationInterpolator}. */
    084        private ConfigurationInterpolator interpolator;
    085
    086        /** The parent {@code ConfigurationInterpolator}. */
    087        private ConfigurationInterpolator parentInterpolator;
    088
    089        /** Function used to convert interpolated values to strings. */
    090        private Function<Object, String> stringConverter;
    091
    092        public Builder() {
    093            prefixLookups = new HashMap<>();
    094            defLookups = new LinkedList<>();
    095        }
    096
    097        /**
    098         * Creates a new {@code InterpolatorSpecification} instance with the properties set so far. After that this builder
    099         * instance is reset so that it can be reused for creating further specification objects.
    100         *
    101         * @return the newly created {@code InterpolatorSpecification}
    102         */
    103        public InterpolatorSpecification create() {
    104            final InterpolatorSpecification spec = new InterpolatorSpecification(this);
    105            reset();
    106            return spec;
    107        }
    108
    109        /**
    110         * Removes all data from this builder. Afterwards it can be used to define a brand new {@code InterpolatorSpecification}
    111         * object.
    112         */
    113        public void reset() {
    114            interpolator = null;
    115            parentInterpolator = null;
    116            prefixLookups.clear();
    117            defLookups.clear();
    118            stringConverter = null;
    119        }
    120
    121        /**
    122         * Adds the given {@code Lookup} object to the list of default lookups.
    123         *
    124         * @param lookup the {@code Lookup} (must not be <b>null</b>)
    125         * @return a reference to this builder for method chaining
    126         * @throws IllegalArgumentException if the {@code Lookup} is <b>null</b>
    127         */
    128        public Builder withDefaultLookup(final Lookup lookup) {
    129            checkLookup(lookup);
    130            defLookups.add(lookup);
    131            return this;
    132        }
    133
    134        /**
    135         * Adds the content of the given collection to the default lookups managed by this builder. The collection can be
    136         * <b>null</b>, then this method has no effect.
    137         *
    138         * @param lookups the collection with lookups to be added
    139         * @return a reference to this builder for method chaining
    140         * @throws IllegalArgumentException if the collection contains <b>null</b> entries
    141         */
    142        public Builder withDefaultLookups(final Collection<? extends Lookup> lookups) {
    143            if (lookups != null) {
    144                lookups.forEach(this::withDefaultLookup);
    145            }
    146            return this;
    147        }
    148
    149        /**
    150         * Sets the {@code ConfigurationInterpolator} instance for the {@code InterpolatorSpecification}. This means that a
    151         * {@code ConfigurationInterpolator} has been created and set up externally and can be used directly.
    152         *
    153         * @param ci the {@code ConfigurationInterpolator} (can be <b>null</b>)
    154         * @return a reference to this builder for method chaining
    155         */
    156        public Builder withInterpolator(final ConfigurationInterpolator ci) {
    157            interpolator = ci;
    158            return this;
    159        }
    160
    161        /**
    162         * Sets an optional parent {@code ConfigurationInterpolator}. If defined, this object is set as parent of a newly
    163         * created {@code ConfigurationInterpolator} instance.
    164         *
    165         * @param parent the parent {@code ConfigurationInterpolator} (can be <b>null</b>)
    166         * @return a reference to this builder for method chaining
    167         */
    168        public Builder withParentInterpolator(final ConfigurationInterpolator parent) {
    169            parentInterpolator = parent;
    170            return this;
    171        }
    172
    173        /**
    174         * Adds a {@code Lookup} object for a given prefix.
    175         *
    176         * @param prefix the prefix (must not be <b>null</b>)
    177         * @param lookup the {@code Lookup} (must not be <b>null</b>)
    178         * @return a reference to this builder for method chaining
    179         * @throws IllegalArgumentException if a required parameter is missing
    180         */
    181        public Builder withPrefixLookup(final String prefix, final Lookup lookup) {
    182            if (prefix == null) {
    183                throw new IllegalArgumentException("Prefix must not be null!");
    184            }
    185            checkLookup(lookup);
    186            prefixLookups.put(prefix, lookup);
    187            return this;
    188        }
    189
    190        /**
    191         * Adds the content of the given map to the prefix lookups managed by this builder. The map can be <b>null</b>, then
    192         * this method has no effect.
    193         *
    194         * @param lookups the map with prefix lookups to be added
    195         * @return a reference to this builder for method chaining
    196         * @throws IllegalArgumentException if the map contains <b>null</b> values
    197         */
    198        public Builder withPrefixLookups(final Map<String, ? extends Lookup> lookups) {
    199            if (lookups != null) {
    200                lookups.forEach(this::withPrefixLookup);
    201            }
    202            return this;
    203        }
    204
    205        /**
    206         * Sets the function used to convert interpolated values to strings. Pass {@code null}
    207         * if the default conversion function is to be used.
    208         *
    209         * @param fn function used to convert interpolated values to string or {@code null} if the
    210         *      default conversion function is to be used
    211         * @return a reference to this builder for method chaining
    212         */
    213        public Builder withStringConverter(final Function<Object, String> fn) {
    214            this.stringConverter = fn;
    215            return this;
    216        }
    217    }
    218
    219    /** The {@code ConfigurationInterpolator} instance to be used directly. */
    220    private final ConfigurationInterpolator interpolator;
    221
    222    /** The parent {@code ConfigurationInterpolator}. */
    223    private final ConfigurationInterpolator parentInterpolator;
    224
    225    /** The map with prefix lookups. */
    226    private final Map<String, Lookup> prefixLookups;
    227
    228    /** The collection with default lookups. */
    229    private final Collection<Lookup> defaultLookups;
    230
    231    /** Function used to convert interpolated values to strings. */
    232    private final Function<Object, String> stringConverter;
    233
    234    /**
    235     * Creates a new instance of {@code InterpolatorSpecification} with the properties defined by the given builder object.
    236     *
    237     * @param builder the builder
    238     */
    239    private InterpolatorSpecification(final Builder builder) {
    240        interpolator = builder.interpolator;
    241        parentInterpolator = builder.parentInterpolator;
    242        prefixLookups = Collections.unmodifiableMap(new HashMap<>(builder.prefixLookups));
    243        defaultLookups = Collections.unmodifiableCollection(new ArrayList<>(builder.defLookups));
    244        stringConverter = builder.stringConverter;
    245    }
    246
    247    /**
    248     * Gets a collection with the default lookups.
    249     *
    250     * @return the default lookups for a new {@code ConfigurationInterpolator} instance (never <b>null</b>)
    251     */
    252    public Collection<Lookup> getDefaultLookups() {
    253        return defaultLookups;
    254    }
    255
    256    /**
    257     * Gets the {@code ConfigurationInterpolator} instance to be used directly.
    258     *
    259     * @return the {@code ConfigurationInterpolator} (can be <b>null</b>)
    260     */
    261    public ConfigurationInterpolator getInterpolator() {
    262        return interpolator;
    263    }
    264
    265    /**
    266     * Gets the parent {@code ConfigurationInterpolator} object.
    267     *
    268     * @return the parent {@code ConfigurationInterpolator} (can be <b>null</b>)
    269     */
    270    public ConfigurationInterpolator getParentInterpolator() {
    271        return parentInterpolator;
    272    }
    273
    274    /**
    275     * Gets a map with prefix lookups. The keys of the map are the prefix strings, its values are the corresponding
    276     * {@code Lookup} objects.
    277     *
    278     * @return the prefix lookups for a new {@code ConfigurationInterpolator} instance (never <b>null</b>)
    279     */
    280    public Map<String, Lookup> getPrefixLookups() {
    281        return prefixLookups;
    282    }
    283
    284    /**
    285     * Gets the function used to convert interpolated values to strings or {@code null}
    286     * if the default conversion function is to be used.
    287     *
    288     * @return function used to convert interpolated values to strings or {@code null} if
    289     *      the default conversion function is to be used
    290     */
    291    public Function<Object, String> getStringConverter() {
    292        return stringConverter;
    293    }
    294}