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 * https://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 * <p>
26 * Public access is through {@link StringLookupFactory}.
27 * </p>
28 *
29 * @param <R> A function's return type
30 * @param <P> A function's second input type
31 * @see StringLookupFactory
32 * @since 1.9
33 */
34 final class BiFunctionStringLookup<P, R> implements BiStringLookup<P> {
35
36 /**
37 * Creates a new instance backed by a Function.
38 *
39 * @param <T> the function's input type
40 * @param biFunction the function, may be null.
41 * @return a new instance backed by the given function.
42 */
43 static <U, T> BiFunctionStringLookup<U, T> on(final BiFunction<String, U, T> biFunction) {
44 return new BiFunctionStringLookup<>(biFunction);
45 }
46
47 /**
48 * Creates a new instance backed by a Map. Used by the default lookup.
49 *
50 * @param <T> the map's value type.
51 * @param map the map of keys to values, may be null.
52 * @return a new instance backed by the given map.
53 */
54 static <U, T> BiFunctionStringLookup<U, T> on(final Map<String, T> map) {
55 return on((key, u) -> map.get(key));
56 }
57
58 /**
59 * Function.
60 */
61 private final BiFunction<String, P, R> biFunction;
62
63 /**
64 * Creates a new instance backed by a Function.
65 *
66 * @param biFunction the function, may be null.
67 */
68 private BiFunctionStringLookup(final BiFunction<String, P, R> biFunction) {
69 this.biFunction = biFunction;
70 }
71
72 @Override
73 public String lookup(final String key) {
74 return lookup(key, null);
75 }
76
77 /**
78 * Looks up a String key by applying the function.
79 * <p>
80 * If the function is null, then null is returned. The function result object is converted to a string using
81 * toString().
82 * </p>
83 *
84 * @param key the key to be looked up, may be null.
85 * @return The function result as a string, may be null.
86 */
87 @Override
88 public String lookup(final String key, final P object) {
89 if (biFunction == null) {
90 return null;
91 }
92 final R obj;
93 try {
94 obj = biFunction.apply(key, object);
95 } catch (final SecurityException | NullPointerException | IllegalArgumentException e) {
96 // Squelched. All lookup(String) will return null.
97 // Could be a ConcurrentHashMap and a null key request
98 return null;
99 }
100 return Objects.toString(obj, null);
101 }
102
103 @Override
104 public String toString() {
105 return super.toString() + " [function=" + biFunction + "]";
106 }
107
108 }