| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.lang.text; |
| |
| import java.util.Map; |
| |
| /** |
| * Lookup a String key to a String value. |
| * <p> |
| * This class represents the simplest form of a string to string map. |
| * It has a benefit over a map in that it can create the result on |
| * demand based on the key. |
| * <p> |
| * This class comes complete with various factory methods. |
| * If these do not suffice, you can subclass and implement your own matcher. |
| * <p> |
| * For example, it would be possible to implement a lookup that used the |
| * key as a primary key, and looked up the value on demand from the database |
| * |
| * @author Apache Software Foundation |
| * @since 2.2 |
| * @version $Id$ |
| */ |
| public abstract class StrLookup { |
| |
| /** |
| * Lookup that always returns null. |
| */ |
| private static final StrLookup NONE_LOOKUP; |
| /** |
| * Lookup that uses System properties. |
| */ |
| private static final StrLookup SYSTEM_PROPERTIES_LOOKUP; |
| static { |
| NONE_LOOKUP = new MapStrLookup(null); |
| StrLookup lookup = null; |
| try { |
| lookup = new MapStrLookup(System.getProperties()); |
| } catch (SecurityException ex) { |
| lookup = NONE_LOOKUP; |
| } |
| SYSTEM_PROPERTIES_LOOKUP = lookup; |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Returns a lookup which always returns null. |
| * |
| * @return a lookup that always returns null, not null |
| */ |
| public static StrLookup noneLookup() { |
| return NONE_LOOKUP; |
| } |
| |
| /** |
| * Returns a lookup which uses {@link System#getProperties() System properties} |
| * to lookup the key to value. |
| * <p> |
| * If a security manager blocked access to system properties, then null will |
| * be returned from every lookup. |
| * <p> |
| * If a null key is used, this lookup will throw a NullPointerException. |
| * |
| * @return a lookup using system properties, not null |
| */ |
| public static StrLookup systemPropertiesLookup() { |
| return SYSTEM_PROPERTIES_LOOKUP; |
| } |
| |
| /** |
| * Returns a lookup which looks up values using a map. |
| * <p> |
| * If the map is null, then null will be returned from every lookup. |
| * The map result object is converted to a string using toString(). |
| * |
| * @param map the map of keys to values, may be null |
| * @return a lookup using the map, not null |
| */ |
| public static StrLookup mapLookup(Map map) { |
| return new MapStrLookup(map); |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Constructor. |
| */ |
| protected StrLookup() { |
| super(); |
| } |
| |
| /** |
| * Looks up a String key to a String value. |
| * <p> |
| * The internal implementation may use any mechanism to return the value. |
| * The simplest implementation is to use a Map. However, virtually any |
| * implementation is possible. |
| * <p> |
| * For example, it would be possible to implement a lookup that used the |
| * key as a primary key, and looked up the value on demand from the database |
| * Or, a numeric based implementation could be created that treats the key |
| * as an integer, increments the value and return the result as a string - |
| * converting 1 to 2, 15 to 16 etc. |
| * <p> |
| * The {@link #lookup(String)} method always returns a String, regardless of |
| * the underlying data, by converting it as necessary. For example: |
| * <pre> |
| * Map map = new HashMap(); |
| * map.put("number", new Integer(2)); |
| * assertEquals("2", StrLookup.mapLookup(map).lookup("number")); |
| * </pre> |
| * @param key the key to be looked up, may be null |
| * @return the matching value, null if no match |
| */ |
| public abstract String lookup(String key); |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Lookup implementation that uses a Map. |
| */ |
| static class MapStrLookup extends StrLookup { |
| |
| /** Map keys are variable names and value. */ |
| private final Map map; |
| |
| /** |
| * Creates a new instance backed by a Map. |
| * |
| * @param map the map of keys to values, may be null |
| */ |
| MapStrLookup(Map map) { |
| this.map = map; |
| } |
| |
| /** |
| * Looks up a String key to a String value using the map. |
| * <p> |
| * If the map is null, then null is returned. |
| * The map result object is converted to a string using toString(). |
| * |
| * @param key the key to be looked up, may be null |
| * @return the matching value, null if no match |
| */ |
| public String lookup(String key) { |
| if (map == null) { |
| return null; |
| } |
| Object obj = map.get(key); |
| if (obj == null) { |
| return null; |
| } |
| return obj.toString(); |
| } |
| } |
| } |