1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.io;
16
17 import com.google.common.annotations.Beta;
18 import com.google.common.annotations.GwtIncompatible;
19 import com.google.common.annotations.VisibleForTesting;
20 import java.io.Closeable;
21 import java.io.IOException;
22 import java.io.InputStream;
23 import java.io.Reader;
24 import java.util.logging.Level;
25 import java.util.logging.Logger;
26 import javax.annotation.CheckForNull;
27
28 /**
29 * Utility methods for working with {@link Closeable} objects.
30 *
31 * @author Michael Lancaster
32 * @since 1.0
33 */
34 @Beta
35 @GwtIncompatible
36 @ElementTypesAreNonnullByDefault
37 public final class Closeables {
38 @VisibleForTesting static final Logger logger = Logger.getLogger(Closeables.class.getName());
39
40 private Closeables() {}
41
42 /**
43 * Closes a {@link Closeable}, with control over whether an {@code IOException} may be thrown.
44 * This is primarily useful in a finally block, where a thrown exception needs to be logged but
45 * not propagated (otherwise the original exception will be lost).
46 *
47 * <p>If {@code swallowIOException} is true then we never throw {@code IOException} but merely log
48 * it.
49 *
50 * <p>Example:
51 *
52 * <pre>{@code
53 * public void useStreamNicely() throws IOException {
54 * SomeStream stream = new SomeStream("foo");
55 * boolean threw = true;
56 * try {
57 * // ... code which does something with the stream ...
58 * threw = false;
59 * } finally {
60 * // If an exception occurs, rethrow it only if threw==false:
61 * Closeables.close(stream, threw);
62 * }
63 * }
64 * }</pre>
65 *
66 * @param closeable the {@code Closeable} object to be closed, or null, in which case this method
67 * does nothing
68 * @param swallowIOException if true, don't propagate IO exceptions thrown by the {@code close}
69 * methods
70 * @throws IOException if {@code swallowIOException} is false and {@code close} throws an {@code
71 * IOException}.
72 */
73 public static void close(@CheckForNull Closeable closeable, boolean swallowIOException)
74 throws IOException {
75 if (closeable == null) {
76 return;
77 }
78 try {
79 closeable.close();
80 } catch (IOException e) {
81 if (swallowIOException) {
82 logger.log(Level.WARNING, "IOException thrown while closing Closeable.", e);
83 } else {
84 throw e;
85 }
86 }
87 }
88
89 /**
90 * Closes the given {@link InputStream}, logging any {@code IOException} that's thrown rather than
91 * propagating it.
92 *
93 * <p>While it's not safe in the general case to ignore exceptions that are thrown when closing an
94 * I/O resource, it should generally be safe in the case of a resource that's being used only for
95 * reading, such as an {@code InputStream}. Unlike with writable resources, there's no chance that
96 * a failure that occurs when closing the stream indicates a meaningful problem such as a failure
97 * to flush all bytes to the underlying resource.
98 *
99 * @param inputStream the input stream to be closed, or {@code null} in which case this method
100 * does nothing
101 * @since 17.0
102 */
103 public static void closeQuietly(@CheckForNull InputStream inputStream) {
104 try {
105 close(inputStream, true);
106 } catch (IOException impossible) {
107 throw new AssertionError(impossible);
108 }
109 }
110
111 /**
112 * Closes the given {@link Reader}, logging any {@code IOException} that's thrown rather than
113 * propagating it.
114 *
115 * <p>While it's not safe in the general case to ignore exceptions that are thrown when closing an
116 * I/O resource, it should generally be safe in the case of a resource that's being used only for
117 * reading, such as a {@code Reader}. Unlike with writable resources, there's no chance that a
118 * failure that occurs when closing the reader indicates a meaningful problem such as a failure to
119 * flush all bytes to the underlying resource.
120 *
121 * @param reader the reader to be closed, or {@code null} in which case this method does nothing
122 * @since 17.0
123 */
124 public static void closeQuietly(@CheckForNull Reader reader) {
125 try {
126 close(reader, true);
127 } catch (IOException impossible) {
128 throw new AssertionError(impossible);
129 }
130 }
131 }