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