1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.commons.text.lookup;
18
19 import java.util.Map;
20 import java.util.Objects;
21 import java.util.function.BiFunction;
22
23 /**
24 * A function-based lookup where the request for a lookup is answered by applying that function with a key.
25 *
26 * @param <R> A function's return type
27 * @param <P> A function's second input type
28 *
29 * @since 1.9
30 */
31 final class BiFunctionStringLookup<P, R> implements BiStringLookup<P> {
32
33 /**
34 * Creates a new instance backed by a Function.
35 *
36 * @param <T> the function's input type
37 * @param biFunction the function, may be null.
38 * @return a new instance backed by the given function.
39 */
40 static <U, T> BiFunctionStringLookup<U, T> on(final BiFunction<String, U, T> biFunction) {
41 return new BiFunctionStringLookup<>(biFunction);
42 }
43
44 /**
45 * Creates a new instance backed by a Map. Used by the default lookup.
46 *
47 * @param <T> the map's value type.
48 * @param map the map of keys to values, may be null.
49 * @return a new instance backed by the given map.
50 */
51 static <U, T> BiFunctionStringLookup<U, T> on(final Map<String, T> map) {
52 return on((key, u) -> map.get(key));
53 }
54
55 /**
56 * Function.
57 */
58 private final BiFunction<String, P, R> biFunction;
59
60 /**
61 * Creates a new instance backed by a Function.
62 *
63 * @param biFunction the function, may be null.
64 */
65 private BiFunctionStringLookup(final BiFunction<String, P, R> biFunction) {
66 this.biFunction = biFunction;
67 }
68
69 @Override
70 public String lookup(final String key) {
71 return lookup(key, null);
72 }
73
74 /**
75 * Looks up a String key by applying the function.
76 * <p>
77 * If the function is null, then null is returned. The function result object is converted to a string using
78 * toString().
79 * </p>
80 *
81 * @param key the key to be looked up, may be null.
82 * @return The function result as a string, may be null.
83 */
84 @Override
85 public String lookup(final String key, final P object) {
86 if (biFunction == null) {
87 return null;
88 }
89 final R obj;
90 try {
91 obj = biFunction.apply(key, object);
92 } catch (final SecurityException | NullPointerException | IllegalArgumentException e) {
93 // Squelched. All lookup(String) will return null.
94 // Could be a ConcurrentHashMap and a null key request
95 return null;
96 }
97 return Objects.toString(obj, null);
98 }
99
100 @Override
101 public String toString() {
102 return super.toString() + " [function=" + biFunction + "]";
103 }
104
105 }