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 */ 100 public static StrLookup<String> resourceBundleLookup(final ResourceBundle resourceBundle) { 101 return new ResourceBundleLookup(resourceBundle); 102 } 103 104 // ----------------------------------------------------------------------- 105 /** 106 * Constructor. 107 */ 108 protected StrLookup() { 109 super(); 110 } 111 112 // ----------------------------------------------------------------------- 113 /** 114 * Lookup implementation that uses a Map. 115 * 116 * @param <V> the type of the values supported by the lookup 117 */ 118 static class MapStrLookup<V> extends StrLookup<V> { 119 120 /** Map keys are variable names and value. */ 121 private final Map<String, V> map; 122 123 /** 124 * Creates a new instance backed by a Map. 125 * 126 * @param map the map of keys to values, may be null 127 */ 128 MapStrLookup(final Map<String, V> map) { 129 this.map = map; 130 } 131 132 /** 133 * Looks up a String key to a String value using the map. 134 * <p> 135 * If the map is null, then null is returned. The map result object is converted to a string using toString(). 136 * 137 * @param key the key to be looked up, may be null 138 * @return the matching value, null if no match 139 */ 140 @Override 141 public String lookup(final String key) { 142 if (map == null) { 143 return null; 144 } 145 final Object obj = map.get(key); 146 if (obj == null) { 147 return null; 148 } 149 return obj.toString(); 150 } 151 152 @Override 153 public String toString() { 154 return super.toString() + " [map=" + map + "]"; 155 } 156 } 157 158 // ----------------------------------------------------------------------- 159 /** 160 * Lookup implementation based on a ResourceBundle. 161 */ 162 private static final class ResourceBundleLookup extends StrLookup<String> { 163 164 /** ResourceBundle keys are variable names and value. */ 165 private final ResourceBundle resourceBundle; 166 167 /** 168 * Creates a new instance backed by a ResourceBundle. 169 * 170 * @param resourceBundle the ResourceBundle of keys to values, may be null 171 */ 172 private ResourceBundleLookup(final ResourceBundle resourceBundle) { 173 this.resourceBundle = resourceBundle; 174 } 175 176 @Override 177 public String lookup(final String key) { 178 if (resourceBundle == null || key == null || !resourceBundle.containsKey(key)) { 179 return null; 180 } 181 return resourceBundle.getString(key); 182 } 183 184 @Override 185 public String toString() { 186 return super.toString() + " [resourceBundle=" + resourceBundle + "]"; 187 } 188 189 } 190 191 // ----------------------------------------------------------------------- 192 /** 193 * Lookup implementation based on system properties. 194 */ 195 private static final class SystemPropertiesStrLookup extends StrLookup<String> { 196 /** 197 * {@inheritDoc} This implementation directly accesses system properties. 198 */ 199 @Override 200 public String lookup(final String key) { 201 if (key.length() > 0) { 202 try { 203 return System.getProperty(key); 204 } catch (final SecurityException scex) { 205 // Squelched. All lookup(String) will return null. 206 return null; 207 } 208 } 209 return null; 210 } 211 } 212}