    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.Map;
    020import java.util.ResourceBundle;
    021
    022import org.apache.commons.text.lookup.StringLookup;
    023import org.apache.commons.text.lookup.StringLookupFactory;
    024
    025/**
    026 * Lookup a String key to a String value.
    027 * <p>
    028 * This class represents the simplest form of a string to string map. It has a benefit over a map in that it can create
    029 * the result on demand based on the key.
    030 * <p>
    031 * This class comes complete with various factory methods. If these do not suffice, you can subclass and implement your
    032 * own matcher.
    033 * <p>
    034 * For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value
    035 * on demand from the database
    036 *
    037 * @param <V> the type of the values supported by the lookup
    038 * @since 1.0
    039 * @deprecated Deprecated as of 1.3, use {@link StringLookupFactory} instead. This class will be removed in 2.0.
    040 */
    041@Deprecated
    042public abstract class StrLookup<V> implements StringLookup {
    043
    044    /**
    045     * Lookup that always returns null.
    046     */
    047    private static final StrLookup<String> NONE_LOOKUP = new MapStrLookup<>(null);
    048
    049    /**
    050     * Lookup based on system properties.
    051     */
    052    private static final StrLookup<String> SYSTEM_PROPERTIES_LOOKUP = new SystemPropertiesStrLookup();
    053
    054    // -----------------------------------------------------------------------
    055    /**
    056     * Returns a lookup which always returns null.
    057     *
    058     * @return a lookup that always returns null, not null
    059     */
    060    public static StrLookup<?> noneLookup() {
    061        return NONE_LOOKUP;
    062    }
    063
    064    /**
    065     * Returns a new lookup which uses a copy of the current {@link System#getProperties() System properties}.
    066     * <p>
    067     * If a security manager blocked access to system properties, then null will be returned from every lookup.
    068     * <p>
    069     * If a null key is used, this lookup will throw a NullPointerException.
    070     *
    071     * @return a lookup using system properties, not null
    072     */
    073    public static StrLookup<String> systemPropertiesLookup() {
    074        return SYSTEM_PROPERTIES_LOOKUP;
    075    }
    076
    077    /**
    078     * Returns a lookup which looks up values using a map.
    079     * <p>
    080     * If the map is null, then null will be returned from every lookup. The map result object is converted to a string
    081     * using toString().
    082     *
    083     * @param <V> the type of the values supported by the lookup
    084     * @param map the map of keys to values, may be null
    085     * @return a lookup using the map, not null
    086     */
    087    public static <V> StrLookup<V> mapLookup(final Map<String, V> map) {
    088        return new MapStrLookup<>(map);
    089    }
    090
    091    /**
    092     * Returns a lookup which looks up values using a ResourceBundle.
    093     * <p>
    094     * If the ResourceBundle is null, then null will be returned from every lookup. The map result object is converted
    095     * to a string using toString().
    096     *
    097     * @param resourceBundle the map of keys to values, may be null
    098     * @return a lookup using the map, not null
    099     * @see StringLookupFactory#resourceBundleStringLookup(String)
    100     */
    101    public static StrLookup<String> resourceBundleLookup(final ResourceBundle resourceBundle) {
    102        return new ResourceBundleLookup(resourceBundle);
    103    }
    104
    105    // -----------------------------------------------------------------------
    106    /**
    107     * Constructor.
    108     */
    109    protected StrLookup() {
    110        super();
    111    }
    112
    113    // -----------------------------------------------------------------------
    114    /**
    115     * Lookup implementation that uses a Map.
    116     *
    117     * @param <V> the type of the values supported by the lookup
    118     */
    119    static class MapStrLookup<V> extends StrLookup<V> {
    120
    121        /** Map keys are variable names and value. */
    122        private final Map<String, V> map;
    123
    124        /**
    125         * Creates a new instance backed by a Map.
    126         *
    127         * @param map the map of keys to values, may be null
    128         */
    129        MapStrLookup(final Map<String, V> map) {
    130            this.map = map;
    131        }
    132
    133        /**
    134         * Looks up a String key to a String value using the map.
    135         * <p>
    136         * If the map is null, then null is returned. The map result object is converted to a string using toString().
    137         *
    138         * @param key the key to be looked up, may be null
    139         * @return the matching value, null if no match
    140         */
    141        @Override
    142        public String lookup(final String key) {
    143            if (map == null) {
    144                return null;
    145            }
    146            final Object obj = map.get(key);
    147            if (obj == null) {
    148                return null;
    149            }
    150            return obj.toString();
    151        }
    152
    153        @Override
    154        public String toString() {
    155            return super.toString() + " [map=" + map + "]";
    156        }
    157    }
    158
    159    // -----------------------------------------------------------------------
    160    /**
    161     * Lookup implementation based on a ResourceBundle.
    162     */
    163    private static final class ResourceBundleLookup extends StrLookup<String> {
    164
    165        /** ResourceBundle keys are variable names and value. */
    166        private final ResourceBundle resourceBundle;
    167
    168        /**
    169         * Creates a new instance backed by a ResourceBundle.
    170         *
    171         * @param resourceBundle the ResourceBundle of keys to values, may be null
    172         */
    173        private ResourceBundleLookup(final ResourceBundle resourceBundle) {
    174            this.resourceBundle = resourceBundle;
    175        }
    176
    177        @Override
    178        public String lookup(final String key) {
    179            if (resourceBundle == null || key == null || !resourceBundle.containsKey(key)) {
    180                return null;
    181            }
    182            return resourceBundle.getString(key);
    183        }
    184
    185        @Override
    186        public String toString() {
    187            return super.toString() + " [resourceBundle=" + resourceBundle + "]";
    188        }
    189
    190    }
    191
    192    // -----------------------------------------------------------------------
    193    /**
    194     * Lookup implementation based on system properties.
    195     */
    196    private static final class SystemPropertiesStrLookup extends StrLookup<String> {
    197        /**
    198         * {@inheritDoc} This implementation directly accesses system properties.
    199         */
    200        @Override
    201        public String lookup(final String key) {
    202            if (key.length() > 0) {
    203                try {
    204                    return System.getProperty(key);
    205                } catch (final SecurityException scex) {
    206                    // Squelched. All lookup(String) will return null.
    207                    return null;
    208                }
    209            }
    210            return null;
    211        }
    212    }
    213}