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.io.input;
18
19 import java.io.IOException;
20 import java.io.InputStream;
21
22 import org.apache.commons.io.function.IOUnaryOperator;
23
24 /**
25 * Proxy stream that prevents the underlying input stream from being closed.
26 * <p>
27 * This class is typically used in cases where an input stream needs to be
28 * passed to a component that wants to explicitly close the stream even if more
29 * input would still be available to other components.
30 * </p>
31 *
32 * @since 1.4
33 */
34 public class CloseShieldInputStream extends ProxyInputStream {
35
36 /**
37 * Constructs a new builder for {@link CloseShieldInputStream}.
38 *
39 * @since 2.22.0
40 */
41 public static class Builder extends AbstractBuilder<CloseShieldInputStream, Builder> {
42
43 private IOUnaryOperator<InputStream> onClose = is -> ClosedInputStream.INSTANCE;
44
45 /**
46 * Constructs a new instance.
47 */
48 public Builder() {
49 // empty
50 }
51
52 @Override
53 public CloseShieldInputStream get() throws IOException {
54 return new CloseShieldInputStream(this);
55 }
56
57 /**
58 * Sets the {@code onClose} function. By default, replaces the underlying input stream when {@link #close()} is called.
59 *
60 * @param onClose the onClose function.
61 * @return {@code this} instance.
62 */
63 public Builder setOnClose(final IOUnaryOperator<InputStream> onClose) {
64 this.onClose = onClose;
65 return asThis();
66 }
67
68 }
69
70 /**
71 * Constructs a new builder for {@link CloseShieldInputStream}.
72 *
73 * @return the new builder.
74 * @since 2.22.0
75 */
76 public static Builder builder() {
77 return new Builder();
78 }
79
80 /**
81 * Constructs a proxy that only shields {@link System#in} from closing.
82 *
83 * @param inputStream the candidate input stream.
84 * @return the given stream or a proxy on {@link System#in}.
85 * @since 2.17.0
86 */
87 public static InputStream systemIn(final InputStream inputStream) {
88 return inputStream == System.in ? wrap(inputStream) : inputStream;
89 }
90
91 /**
92 * Constructs a proxy that shields the given input stream from being closed.
93 *
94 * @param inputStream the input stream to wrap.
95 * @return the created proxy.
96 * @since 2.9.0
97 */
98 public static CloseShieldInputStream wrap(final InputStream inputStream) {
99 return new CloseShieldInputStream(inputStream);
100 }
101
102 private final IOUnaryOperator<InputStream> onClose;
103
104 private CloseShieldInputStream(final Builder builder) throws IOException {
105 super(builder.getInputStream());
106 this.onClose = builder.onClose;
107 }
108
109 /**
110 * Constructs a proxy that shields the given input stream from being closed.
111 *
112 * @param inputStream underlying input stream.
113 * @deprecated Using this constructor prevents IDEs from warning if the
114 * underlying input stream is never closed. Use
115 * {@link #wrap(InputStream)} instead.
116 */
117 @Deprecated
118 public CloseShieldInputStream(final InputStream inputStream) {
119 super(inputStream);
120 this.onClose = builder().onClose;
121 }
122
123 /**
124 * Applies the {@code onClose} function to the underlying input stream, replacing it with the result.
125 * <p>
126 * By default, replaces the underlying input stream with a {@link ClosedInputStream} sentinel. The original input stream will remain open, but this proxy
127 * will appear closed.
128 * </p>
129 *
130 * @throws IOException Thrown by the {@code onClose} function.
131 */
132 @Override
133 public void close() throws IOException {
134 in = onClose.apply(in);
135 }
136
137 }