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.io.input;
18
19 import java.io.IOException;
20 import java.io.InputStream;
21 import java.io.Serializable;
22 import java.util.UUID;
23
24 import org.apache.commons.io.TaggedIOException;
25
26 /**
27 * An input stream decorator that tags potential exceptions so that the
28 * stream that caused the exception can easily be identified. This is
29 * done by using the {@link TaggedIOException} class to wrap all thrown
30 * {@link IOException}s. See below for an example of using this class.
31 * <pre>
32 * TaggedInputStream stream = new TaggedInputStream(...);
33 * try {
34 * // Processing that may throw an IOException either from this stream
35 * // or from some other IO activity like temporary files, etc.
36 * processStream(stream);
37 * } catch (IOException e) {
38 * if (stream.isCauseOf(e)) {
39 * // The exception was caused by this stream.
40 * // Use e.getCause() to get the original exception.
41 * } else {
42 * // The exception was caused by something else.
43 * }
44 * }
45 * </pre>
46 * <p>
47 * Alternatively, the {@link #throwIfCauseOf(Throwable)} method can be
48 * used to let higher levels of code handle the exception caused by this
49 * stream while other processing errors are being taken care of at this
50 * lower level.
51 * </p>
52 * <pre>
53 * TaggedInputStream stream = new TaggedInputStream(...);
54 * try {
55 * processStream(stream);
56 * } catch (IOException e) {
57 * stream.throwIfCauseOf(e);
58 * // ... or process the exception that was caused by something else
59 * }
60 * </pre>
61 * <h2>Deprecating Serialization</h2>
62 * <p>
63 * <em>Serialization is deprecated and will be removed in 3.0.</em>
64 * </p>
65 *
66 * @see TaggedIOException
67 * @since 2.0
68 */
69 public class TaggedInputStream extends ProxyInputStream {
70
71 /**
72 * The unique tag associated with exceptions from stream.
73 */
74 private final Serializable tag = UUID.randomUUID();
75
76 /**
77 * Constructs a tagging decorator for the given input stream.
78 *
79 * @param proxy input stream to be decorated
80 */
81 public TaggedInputStream(final InputStream proxy) {
82 super(proxy);
83 }
84
85 /**
86 * Tags any IOExceptions thrown, wrapping and re-throwing.
87 *
88 * @param e The IOException thrown
89 * @throws IOException if an I/O error occurs.
90 */
91 @Override
92 protected void handleIOException(final IOException e) throws IOException {
93 throw new TaggedIOException(e, tag);
94 }
95
96 /**
97 * Tests if the given exception was caused by this stream.
98 *
99 * @param exception an exception
100 * @return {@code true} if the exception was thrown by this stream,
101 * {@code false} otherwise
102 */
103 public boolean isCauseOf(final Throwable exception) {
104 return TaggedIOException.isTaggedWith(exception, tag);
105 }
106
107 /**
108 * Re-throws the original exception thrown by this stream. This method
109 * first checks whether the given exception is a {@link TaggedIOException}
110 * wrapper created by this decorator, and then unwraps and throws the
111 * original wrapped exception. Returns normally if the exception was
112 * not thrown by this stream.
113 *
114 * @param throwable an exception
115 * @throws IOException original exception, if any, thrown by this stream
116 */
117 public void throwIfCauseOf(final Throwable throwable) throws IOException {
118 TaggedIOException.throwCauseIfTaggedWith(throwable, tag);
119 }
120
121 }