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
18 package org.apache.commons.io.function;
19
20 import java.io.IOException;
21 import java.io.UncheckedIOException;
22 import java.util.Objects;
23 import java.util.function.Consumer;
24 import java.util.function.Function;
25 import java.util.function.Supplier;
26
27 /**
28 * Like {@link Function} but throws {@link IOException}.
29 *
30 * @param <T> the type of the input to the operations.
31 * @param <R> the return type of the operations.
32 * @since 2.7
33 */
34 @FunctionalInterface
35 public interface IOFunction<T, R> {
36
37 /**
38 * Returns a {@link IOFunction} that always returns its input argument.
39 *
40 * @param <T> the type of the input and output objects to the function
41 * @return a function that always returns its input argument
42 */
43 @SuppressWarnings("unchecked")
44 static <T> IOFunction<T, T> identity() {
45 return Constants.IO_FUNCTION_ID;
46 }
47
48 /**
49 * Returns a composed {@link IOFunction} that first applies this function to its input, and then applies the
50 * {@code after} consumer to the result. If evaluation of either function throws an exception, it is relayed to the
51 * caller of the composed function.
52 *
53 * @param after the consumer to apply after this function is applied
54 * @return a composed function that first applies this function and then applies the {@code after} consumer
55 * @throws NullPointerException if after is null
56 * @see #compose(IOFunction)
57 */
58 default IOConsumer<T> andThen(final Consumer<? super R> after) {
59 Objects.requireNonNull(after, "after");
60 return (final T t) -> after.accept(apply(t));
61 }
62
63 /**
64 * Returns a composed {@link IOFunction} that first applies this function to its input, and then applies the
65 * {@code after} function to the result. If evaluation of either function throws an exception, it is relayed to the
66 * caller of the composed function.
67 *
68 * @param <V> the type of output of the {@code after} function, and of the composed function
69 * @param after the function to apply after this function is applied
70 * @return a composed function that first applies this function and then applies the {@code after} function
71 * @throws NullPointerException if after is null
72 * @see #compose(IOFunction)
73 */
74 default <V> IOFunction<T, V> andThen(final Function<? super R, ? extends V> after) {
75 Objects.requireNonNull(after, "after");
76 return (final T t) -> after.apply(apply(t));
77 }
78
79 /**
80 * Returns a composed {@link IOFunction} that first applies this function to its input, and then applies the
81 * {@code after} consumer to the result. If evaluation of either function throws an exception, it is relayed to the
82 * caller of the composed function.
83 *
84 * @param after the consumer to apply after this function is applied
85 * @return a composed function that first applies this function and then applies the {@code after} consumer
86 * @throws NullPointerException if after is null
87 * @see #compose(IOFunction)
88 */
89 default IOConsumer<T> andThen(final IOConsumer<? super R> after) {
90 Objects.requireNonNull(after, "after");
91 return (final T t) -> after.accept(apply(t));
92 }
93
94 /**
95 * Returns a composed {@link IOFunction} that first applies this function to its input, and then applies the
96 * {@code after} function to the result. If evaluation of either function throws an exception, it is relayed to the
97 * caller of the composed function.
98 *
99 * @param <V> the type of output of the {@code after} function, and of the composed function
100 * @param after the function to apply after this function is applied
101 * @return a composed function that first applies this function and then applies the {@code after} function
102 * @throws NullPointerException if after is null
103 * @see #compose(IOFunction)
104 */
105 default <V> IOFunction<T, V> andThen(final IOFunction<? super R, ? extends V> after) {
106 Objects.requireNonNull(after, "after");
107 return (final T t) -> after.apply(apply(t));
108 }
109
110 /**
111 * Applies this function to the given argument.
112 *
113 * @param t the function argument
114 * @return the function result
115 * @throws IOException if an I/O error occurs.
116 */
117 R apply(T t) throws IOException;
118
119 /**
120 * Creates a {@link Function} for this instance that throws {@link UncheckedIOException} instead of {@link IOException}.
121 *
122 * @return an UncheckedIOException Function.
123 * @since 2.12.0
124 */
125 default Function<T, R> asFunction() {
126 return t -> Uncheck.apply(this, t);
127 }
128
129 /**
130 * Returns a composed {@link IOFunction} that first applies the {@code before} function to its input, and then applies
131 * this function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the
132 * composed function.
133 *
134 * @param <V> the type of input to the {@code before} function, and to the composed function
135 * @param before the function to apply before this function is applied
136 * @return a composed function that first applies the {@code before} function and then applies this function
137 * @throws NullPointerException if before is null
138 * @see #andThen(IOFunction)
139 */
140 default <V> IOFunction<V, R> compose(final Function<? super V, ? extends T> before) {
141 Objects.requireNonNull(before, "before");
142 return (final V v) -> apply(before.apply(v));
143 }
144
145 /**
146 * Returns a composed {@link IOFunction} that first applies the {@code before} function to its input, and then applies
147 * this function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the
148 * composed function.
149 *
150 * @param <V> the type of input to the {@code before} function, and to the composed function
151 * @param before the function to apply before this function is applied
152 * @return a composed function that first applies the {@code before} function and then applies this function
153 * @throws NullPointerException if before is null
154 * @see #andThen(IOFunction)
155 */
156 default <V> IOFunction<V, R> compose(final IOFunction<? super V, ? extends T> before) {
157 Objects.requireNonNull(before, "before");
158 return (final V v) -> apply(before.apply(v));
159 }
160
161 /**
162 * Returns a composed {@link IOFunction} that first applies the {@code before} function to its input, and then applies
163 * this function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the
164 * composed function.
165 *
166 * @param before the supplier which feeds the application of this function
167 * @return a composed function that first applies the {@code before} function and then applies this function
168 * @throws NullPointerException if before is null
169 * @see #andThen(IOFunction)
170 */
171 default IOSupplier<R> compose(final IOSupplier<? extends T> before) {
172 Objects.requireNonNull(before, "before");
173 return () -> apply(before.get());
174 }
175
176 /**
177 * Returns a composed {@link IOFunction} that first applies the {@code before} function to its input, and then applies
178 * this function to the result. If evaluation of either function throws an exception, it is relayed to the caller of the
179 * composed function.
180 *
181 * @param before the supplier which feeds the application of this function
182 * @return a composed function that first applies the {@code before} function and then applies this function
183 * @throws NullPointerException if before is null
184 * @see #andThen(IOFunction)
185 */
186 default IOSupplier<R> compose(final Supplier<? extends T> before) {
187 Objects.requireNonNull(before, "before");
188 return () -> apply(before.get());
189 }
190 }