1 package org.eclipse.aether.spi.connector.checksum;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import org.eclipse.aether.transfer.ChecksumFailureException;
23
24 /**
25 * A checksum policy gets employed by repository connectors to validate the integrity of a downloaded file. For each
26 * downloaded file, a checksum policy instance is obtained and presented with the available checksums to conclude
27 * whether the download is valid or not. The following pseudo-code illustrates the usage of a checksum policy by a
28 * repository connector in some more detail (the retry logic has been omitted for the sake of brevity):
29 *
30 * <pre>
31 * void validateChecksums() throws ChecksumFailureException {
32 * for (checksum : checksums) {
33 * switch (checksum.state) {
34 * case MATCH:
35 * if (policy.onChecksumMatch(...)) {
36 * return;
37 * }
38 * break;
39 * case MISMATCH:
40 * policy.onChecksumMismatch(...);
41 * break;
42 * case ERROR:
43 * policy.onChecksumError(...);
44 * break;
45 * }
46 * }
47 * policy.onNoMoreChecksums();
48 * }
49 *
50 * void downloadFile() throws Exception {
51 * ...
52 * policy = newChecksumPolicy();
53 * try {
54 * validateChecksums();
55 * } catch (ChecksumFailureException e) {
56 * if (!policy.onTransferChecksumFailure(...)) {
57 * throw e;
58 * }
59 * }
60 * }
61 * </pre>
62 *
63 * Checksum policies might be stateful and are generally not thread-safe.
64 */
65 public interface ChecksumPolicy
66 {
67
68 /**
69 * Bit flag indicating a checksum which is not part of the official repository layout/structure.
70 */
71 int KIND_UNOFFICIAL = 0x01;
72
73 /**
74 * Signals a match between the locally computed checksum value and the checksum value declared by the remote
75 * repository.
76 *
77 * @param algorithm The name of the checksum algorithm being used, must not be {@code null}.
78 * @param kind A bit field providing further details about the checksum. See the {@code KIND_*} constants in this
79 * interface for possible bit flags.
80 * @return {@code true} to accept the download as valid and stop further validation, {@code false} to continue
81 * validation with the next checksum.
82 */
83 boolean onChecksumMatch( String algorithm, int kind );
84
85 /**
86 * Signals a mismatch between the locally computed checksum value and the checksum value declared by the remote
87 * repository. A simple policy would just rethrow the provided exception. More sophisticated policies could update
88 * their internal state and defer a conclusion until all available checksums have been processed.
89 *
90 * @param algorithm The name of the checksum algorithm being used, must not be {@code null}.
91 * @param kind A bit field providing further details about the checksum. See the {@code KIND_*} constants in this
92 * interface for possible bit flags.
93 * @param exception The exception describing the checksum mismatch, must not be {@code null}.
94 * @throws ChecksumFailureException If the checksum validation is to be failed. If the method returns normally,
95 * validation continues with the next checksum.
96 */
97 void onChecksumMismatch( String algorithm, int kind, ChecksumFailureException exception )
98 throws ChecksumFailureException;
99
100 /**
101 * Signals an error while computing the local checksum value or retrieving the checksum value from the remote
102 * repository.
103 *
104 * @param algorithm The name of the checksum algorithm being used, must not be {@code null}.
105 * @param kind A bit field providing further details about the checksum. See the {@code KIND_*} constants in this
106 * interface for possible bit flags.
107 * @param exception The exception describing the checksum error, must not be {@code null}.
108 * @throws ChecksumFailureException If the checksum validation is to be failed. If the method returns normally,
109 * validation continues with the next checksum.
110 */
111 void onChecksumError( String algorithm, int kind, ChecksumFailureException exception )
112 throws ChecksumFailureException;
113
114 /**
115 * Signals that all available checksums have been processed.
116 *
117 * @throws ChecksumFailureException If the checksum validation is to be failed. If the method returns normally, the
118 * download is assumed to be valid.
119 */
120 void onNoMoreChecksums()
121 throws ChecksumFailureException;
122
123 /**
124 * Signals that the download is being retried after a previously thrown {@link ChecksumFailureException} that is
125 * {@link ChecksumFailureException#isRetryWorthy() retry-worthy}. Policies that maintain internal state will usually
126 * have to reset some of this state at this point to prepare for a new round of validation.
127 */
128 void onTransferRetry();
129
130 /**
131 * Signals that (even after a potential retry) checksum validation has failed. A policy could opt to merely log this
132 * issue or insist on rejecting the downloaded file as unusable.
133 *
134 * @param exception The exception that was thrown from a prior call to
135 * {@link #onChecksumMismatch(String, int, ChecksumFailureException)},
136 * {@link #onChecksumError(String, int, ChecksumFailureException)} or {@link #onNoMoreChecksums()}.
137 * @return {@code true} to accept the download nevertheless and let artifact resolution succeed, {@code false} to
138 * reject the transferred file as unusable.
139 */
140 boolean onTransferChecksumFailure( ChecksumFailureException exception );
141
142 }