Source code
Description: source: package: org.apache.commons.text, class: StrLookup

    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.text;
    018
    019import java.util.Collections;
    020import java.util.Map;
    021import java.util.Objects;
    022import java.util.ResourceBundle;
    023
    024import org.apache.commons.text.lookup.StringLookup;
    025import org.apache.commons.text.lookup.StringLookupFactory;
    026
    027/**
    028 * Lookup a String key to a String value.
    029 * <p>
    030 * This class represents the simplest form of a string to string map. It has a benefit over a map in that it can create
    031 * the result on demand based on the key.
    032 * </p>
    033 * <p>
    034 * This class comes complete with various factory methods. If these do not suffice, you can subclass and implement your
    035 * own matcher.
    036 * </p>
    037 * <p>
    038 * For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value
    039 * on demand from the database
    040 * </p>
    041 *
    042 * @param <V> the type of the values supported by the lookup
    043 * @since 1.0
    044 * @deprecated Deprecated as of 1.3, use {@link StringLookupFactory} instead. This class will be removed in 2.0.
    045 */
    046@Deprecated
    047public abstract class StrLookup<V> implements StringLookup {
    048
    049    /**
    050     * Lookup implementation that uses a Map.
    051     *
    052     * @param <V> the type of the values supported by the lookup
    053     */
    054    private static final class MapStrLookup<V> extends StrLookup<V> {
    055
    056        /** Map keys are variable names and value. */
    057        private final Map<String, V> map;
    058
    059        /**
    060         * Creates a new instance backed by a Map.
    061         *
    062         * @param map the map of keys to values, may be null
    063         */
    064        private MapStrLookup(final Map<String, V> map) {
    065            this.map = map != null ? map : Collections.emptyMap();
    066        }
    067
    068        /**
    069         * Looks up a String key to a String value using the map.
    070         * <p>
    071         * If the map is null, then null is returned. The map result object is converted to a string using toString().
    072         * </p>
    073         *
    074         * @param key the key to be looked up, may be null
    075         * @return The matching value, null if no match
    076         */
    077        @Override
    078        public String lookup(final String key) {
    079            return Objects.toString(map.get(key), null);
    080        }
    081
    082        @Override
    083        public String toString() {
    084            return super.toString() + " [map=" + map + "]";
    085        }
    086    }
    087
    088    /**
    089     * Lookup implementation based on a ResourceBundle.
    090     */
    091    private static final class ResourceBundleLookup extends StrLookup<String> {
    092
    093        /** ResourceBundle keys are variable names and value. */
    094        private final ResourceBundle resourceBundle;
    095
    096        /**
    097         * Creates a new instance backed by a ResourceBundle.
    098         *
    099         * @param resourceBundle the ResourceBundle of keys to values, may be null
    100         */
    101        private ResourceBundleLookup(final ResourceBundle resourceBundle) {
    102            this.resourceBundle = resourceBundle;
    103        }
    104
    105        @Override
    106        public String lookup(final String key) {
    107            if (resourceBundle == null || key == null || !resourceBundle.containsKey(key)) {
    108                return null;
    109            }
    110            return resourceBundle.getString(key);
    111        }
    112
    113        @Override
    114        public String toString() {
    115            return super.toString() + " [resourceBundle=" + resourceBundle + "]";
    116        }
    117
    118    }
    119
    120    /**
    121     * Lookup implementation based on system properties.
    122     */
    123    private static final class SystemPropertiesStrLookup extends StrLookup<String> {
    124
    125        /**
    126         * Private for Spotbugs SING_SINGLETON_GETTER_NOT_SYNCHRONIZED.
    127         */
    128        private SystemPropertiesStrLookup() {
    129            // default
    130        }
    131
    132        /**
    133         * {@inheritDoc} This implementation directly accesses system properties.
    134         */
    135        @Override
    136        public String lookup(final String key) {
    137            if (!key.isEmpty()) {
    138                try {
    139                    return System.getProperty(key);
    140                } catch (final SecurityException ignored) {
    141                    // Noop: All lookup(String) will return null.
    142                }
    143            }
    144            return null;
    145        }
    146    }
    147
    148    /**
    149     * Lookup that always returns null.
    150     */
    151    private static final StrLookup<String> NONE_LOOKUP = new MapStrLookup<>(null);
    152
    153    /**
    154     * Lookup based on system properties.
    155     */
    156    private static final StrLookup<String> SYSTEM_PROPERTIES_LOOKUP = new SystemPropertiesStrLookup();
    157
    158    /**
    159     * Returns a lookup which looks up values using a map.
    160     * <p>
    161     * If the map is null, then null will be returned from every lookup. The map result object is converted to a string
    162     * using toString().
    163     * </p>
    164     *
    165     * @param <V> the type of the values supported by the lookup
    166     * @param map the map of keys to values, may be null
    167     * @return a lookup using the map, not null
    168     */
    169    public static <V> StrLookup<V> mapLookup(final Map<String, V> map) {
    170        return new MapStrLookup<>(map);
    171    }
    172
    173    /**
    174     * Returns a lookup which always returns null.
    175     *
    176     * @return a lookup that always returns null, not null
    177     */
    178    public static StrLookup<?> noneLookup() {
    179        return NONE_LOOKUP;
    180    }
    181
    182    /**
    183     * Returns a lookup which looks up values using a ResourceBundle.
    184     * <p>
    185     * If the ResourceBundle is null, then null will be returned from every lookup. The map result object is converted
    186     * to a string using toString().
    187     * </p>
    188     *
    189     * @param resourceBundle the map of keys to values, may be null
    190     * @return a lookup using the map, not null
    191     * @see StringLookupFactory#resourceBundleStringLookup(String)
    192     */
    193    public static StrLookup<String> resourceBundleLookup(final ResourceBundle resourceBundle) {
    194        return new ResourceBundleLookup(resourceBundle);
    195    }
    196
    197    /**
    198     * Returns a new lookup which uses a copy of the current {@link System#getProperties() System properties}.
    199     * <p>
    200     * If a security manager blocked access to system properties, then null will be returned from every lookup.
    201     * </p>
    202     * <p>
    203     * If a null key is used, this lookup will throw a NullPointerException.
    204     * </p>
    205     *
    206     * @return a lookup using system properties, not null
    207     */
    208    public static StrLookup<String> systemPropertiesLookup() {
    209        return SYSTEM_PROPERTIES_LOOKUP;
    210    }
    211
    212    /**
    213     * Constructs a new instance for subclasses.
    214     */
    215    protected StrLookup() {
    216    }
    217}