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Diffstat (limited to 'src/main/java/org/apache/commons/lang3/text/StrLookup.java')
| -rw-r--r-- | src/main/java/org/apache/commons/lang3/text/StrLookup.java | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/lang3/text/StrLookup.java b/src/main/java/org/apache/commons/lang3/text/StrLookup.java new file mode 100644 index 000000000..52ef035e1 --- /dev/null +++ b/src/main/java/org/apache/commons/lang3/text/StrLookup.java @@ -0,0 +1,187 @@ +/* + * 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.lang3.text; + +import java.util.Map; + +import org.apache.commons.lang3.SystemProperties; + +/** + * 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> + * <p> + * This class comes complete with various factory methods. + * If these do not suffice, you can subclass and implement your own matcher. + * </p> + * <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. + * </p> + * + * @param <V> Unused. + * @since 2.2 + * @deprecated As of 3.6, use Apache Commons Text + * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/lookup/StringLookupFactory.html"> + * StringLookupFactory</a> instead + */ +@Deprecated +public abstract class StrLookup<V> { + + /** + * Lookup that always returns null. + */ + private static final StrLookup<String> NONE_LOOKUP = new MapStrLookup<>(null); + + /** + * Lookup based on system properties. + */ + private static final StrLookup<String> SYSTEM_PROPERTIES_LOOKUP = new SystemPropertiesStrLookup(); + + /** + * 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 new lookup which uses a copy of the current + * {@link System#getProperties() System properties}. + * <p> + * If a security manager blocked access to system properties, then null will + * be returned from every lookup. + * </p> + * <p> + * If a null key is used, this lookup will throw a NullPointerException. + * </p> + * + * @return a lookup using system properties, not null + */ + public static StrLookup<String> 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(). + * </p> + * + * @param <V> the type of the values supported by the lookup + * @param map the map of keys to values, may be null + * @return a lookup using the map, not null + */ + public static <V> StrLookup<V> mapLookup(final Map<String, V> map) { + return new MapStrLookup<>(map); + } + + /** + * Constructor. + */ + protected StrLookup() { + } + + /** + * 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> + * <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> + * <p> + * The {@link #lookup(String)} method always returns a String, regardless of + * the underlying data, by converting it as necessary. For example: + * </p> + * <pre> + * Map<String, Object> map = new HashMap<String, Object>(); + * map.put("number", Integer.valueOf(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. + * + * @param <V> the type of mapped values. + */ + static class MapStrLookup<V> extends StrLookup<V> { + + /** Map keys are variable names and value. */ + private final Map<String, V> map; + + /** + * Creates a new instance backed by a Map. + * + * @param map the map of keys to values, may be null + */ + MapStrLookup(final Map<String, V> 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(). + * </p> + * + * @param key the key to be looked up, may be null + * @return the matching value, null if no match + */ + @Override + public String lookup(final String key) { + if (map == null) { + return null; + } + final Object obj = map.get(key); + if (obj == null) { + return null; + } + return obj.toString(); + } + } + + /** + * Lookup implementation based on system properties. + */ + private static class SystemPropertiesStrLookup extends StrLookup<String> { + /** + * {@inheritDoc} This implementation directly accesses system properties. + */ + @Override + public String lookup(final String key) { + return SystemProperties.getProperty(key); + } + } +} |