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.lang3.text; 018 019import java.util.Map; 020 021/** 022 * Lookup a String key to a String value. 023 * <p> 024 * This class represents the simplest form of a string to string map. 025 * It has a benefit over a map in that it can create the result on 026 * demand based on the key. 027 * <p> 028 * This class comes complete with various factory methods. 029 * If these do not suffice, you can subclass and implement your own matcher. 030 * <p> 031 * For example, it would be possible to implement a lookup that used the 032 * key as a primary key, and looked up the value on demand from the database 033 * 034 * @since 2.2 035 * @deprecated as of 3.6, use commons-text 036 * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/StringLookupFactory.html"> 037 * StringLookupFactory</a> instead 038 */ 039@Deprecated 040public abstract class StrLookup<V> { 041 042 /** 043 * Lookup that always returns null. 044 */ 045 private static final StrLookup<String> NONE_LOOKUP = new MapStrLookup<>(null); 046 047 /** 048 * Lookup based on system properties. 049 */ 050 private static final StrLookup<String> SYSTEM_PROPERTIES_LOOKUP = new SystemPropertiesStrLookup(); 051 052 //----------------------------------------------------------------------- 053 /** 054 * Returns a lookup which always returns null. 055 * 056 * @return a lookup that always returns null, not null 057 */ 058 public static StrLookup<?> noneLookup() { 059 return NONE_LOOKUP; 060 } 061 062 /** 063 * Returns a new lookup which uses a copy of the current 064 * {@link System#getProperties() System properties}. 065 * <p> 066 * If a security manager blocked access to system properties, then null will 067 * 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. 081 * The map result object is converted to a string 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 /** 093 * Constructor. 094 */ 095 protected StrLookup() { 096 super(); 097 } 098 099 /** 100 * Looks up a String key to a String value. 101 * <p> 102 * The internal implementation may use any mechanism to return the value. 103 * The simplest implementation is to use a Map. However, virtually any 104 * implementation is possible. 105 * <p> 106 * For example, it would be possible to implement a lookup that used the 107 * key as a primary key, and looked up the value on demand from the database 108 * Or, a numeric based implementation could be created that treats the key 109 * as an integer, increments the value and return the result as a string - 110 * converting 1 to 2, 15 to 16 etc. 111 * <p> 112 * The {@link #lookup(String)} method always returns a String, regardless of 113 * the underlying data, by converting it as necessary. For example: 114 * <pre> 115 * Map<String, Object> map = new HashMap<String, Object>(); 116 * map.put("number", Integer.valueOf(2)); 117 * assertEquals("2", StrLookup.mapLookup(map).lookup("number")); 118 * </pre> 119 * @param key the key to be looked up, may be null 120 * @return the matching value, null if no match 121 */ 122 public abstract String lookup(String key); 123 124 //----------------------------------------------------------------------- 125 /** 126 * Lookup implementation that uses a Map. 127 */ 128 static class MapStrLookup<V> extends StrLookup<V> { 129 130 /** Map keys are variable names and value. */ 131 private final Map<String, V> map; 132 133 /** 134 * Creates a new instance backed by a Map. 135 * 136 * @param map the map of keys to values, may be null 137 */ 138 MapStrLookup(final Map<String, V> map) { 139 this.map = map; 140 } 141 142 /** 143 * Looks up a String key to a String value using the map. 144 * <p> 145 * If the map is null, then null is returned. 146 * The map result object is converted to a string using toString(). 147 * 148 * @param key the key to be looked up, may be null 149 * @return the matching value, null if no match 150 */ 151 @Override 152 public String lookup(final String key) { 153 if (map == null) { 154 return null; 155 } 156 final Object obj = map.get(key); 157 if (obj == null) { 158 return null; 159 } 160 return obj.toString(); 161 } 162 } 163 164 //----------------------------------------------------------------------- 165 /** 166 * Lookup implementation based on system properties. 167 */ 168 private static class SystemPropertiesStrLookup extends StrLookup<String> { 169 /** 170 * {@inheritDoc} This implementation directly accesses system properties. 171 */ 172 @Override 173 public String lookup(final String key) { 174 if (!key.isEmpty()) { 175 try { 176 return System.getProperty(key); 177 } catch (final SecurityException scex) { 178 // Squelched. All lookup(String) will return null. 179 } 180 } 181 return null; 182 } 183 } 184}