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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.eclipse.aether.transfer;
20  
21  /**
22   * A listener being notified of artifact/metadata transfers from/to remote repositories. The listener may be called from
23   * an arbitrary thread. Reusing common regular expression syntax, the sequence of events is roughly as follows:
24   *
25   * <pre>
26   * INITIATED ( STARTED PROGRESSED* CORRUPTED? )* ( SUCCEEDED | FAILED )
27   * </pre>
28   *
29   * <em>Note:</em> Implementors are strongly advised to inherit from {@link AbstractTransferListener} instead of directly
30   * implementing this interface.
31   *
32   * @see org.eclipse.aether.RepositorySystemSession#getTransferListener()
33   * @see org.eclipse.aether.RepositoryListener
34   * @noimplement This interface is not intended to be implemented by clients.
35   * @noextend This interface is not intended to be extended by clients.
36   */
37  public interface TransferListener {
38  
39      /**
40       * Notifies the listener about the initiation of a transfer. This event gets fired before any actual network access
41       * to the remote repository and usually indicates some thread is now about to perform the transfer. For a given
42       * transfer request, this event is the first one being fired and it must be emitted exactly once.
43       *
44       * @param event The event details, must not be {@code null}.
45       * @throws TransferCancelledException If the transfer should be aborted.
46       */
47      void transferInitiated(TransferEvent event) throws TransferCancelledException;
48  
49      /**
50       * Notifies the listener about the start of a data transfer. This event indicates a successful connection to the
51       * remote repository. In case of a download, the requested remote resource exists and its size is given by
52       * {@link TransferResource#getContentLength()} if possible. This event may be fired multiple times for given
53       * transfer request if said transfer needs to be repeated (e.g. in response to an authentication challenge).
54       *
55       * @param event The event details, must not be {@code null}.
56       * @throws TransferCancelledException If the transfer should be aborted.
57       */
58      void transferStarted(TransferEvent event) throws TransferCancelledException;
59  
60      /**
61       * Notifies the listener about some progress in the data transfer. This event may even be fired if actually zero
62       * bytes have been transferred since the last event, for instance to enable cancellation.
63       *
64       * @param event The event details, must not be {@code null}.
65       * @throws TransferCancelledException If the transfer should be aborted.
66       */
67      void transferProgressed(TransferEvent event) throws TransferCancelledException;
68  
69      /**
70       * Notifies the listener that a checksum validation failed. {@link TransferEvent#getException()} will be of type
71       * {@link ChecksumFailureException} and can be used to query further details about the expected/actual checksums.
72       *
73       * @param event The event details, must not be {@code null}.
74       * @throws TransferCancelledException If the transfer should be aborted.
75       */
76      void transferCorrupted(TransferEvent event) throws TransferCancelledException;
77  
78      /**
79       * Notifies the listener about the successful completion of a transfer. This event must be fired exactly once for a
80       * given transfer request unless said request failed.
81       *
82       * @param event The event details, must not be {@code null}.
83       */
84      void transferSucceeded(TransferEvent event);
85  
86      /**
87       * Notifies the listener about the unsuccessful termination of a transfer. {@link TransferEvent#getException()} will
88       * provide further information about the failure.
89       *
90       * @param event The event details, must not be {@code null}.
91       */
92      void transferFailed(TransferEvent event);
93  }