001package org.eclipse.aether.transfer;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 * 
012 *  http://www.apache.org/licenses/LICENSE-2.0
013 * 
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022/**
023 * A listener being notified of artifact/metadata transfers from/to remote repositories. The listener may be called from
024 * an arbitrary thread. Reusing common regular expression syntax, the sequence of events is roughly as follows:
025 * 
026 * <pre>
027 * INITIATED ( STARTED PROGRESSED* CORRUPTED? )* ( SUCCEEDED | FAILED )
028 * </pre>
029 * 
030 * <em>Note:</em> Implementors are strongly advised to inherit from {@link AbstractTransferListener} instead of directly
031 * implementing this interface.
032 * 
033 * @see org.eclipse.aether.RepositorySystemSession#getTransferListener()
034 * @see org.eclipse.aether.RepositoryListener
035 * @noimplement This interface is not intended to be implemented by clients.
036 * @noextend This interface is not intended to be extended by clients.
037 */
038public interface TransferListener
039{
040
041    /**
042     * Notifies the listener about the initiation of a transfer. This event gets fired before any actual network access
043     * to the remote repository and usually indicates some thread is now about to perform the transfer. For a given
044     * transfer request, this event is the first one being fired and it must be emitted exactly once.
045     * 
046     * @param event The event details, must not be {@code null}.
047     * @throws TransferCancelledException If the transfer should be aborted.
048     */
049    void transferInitiated( TransferEvent event )
050        throws TransferCancelledException;
051
052    /**
053     * Notifies the listener about the start of a data transfer. This event indicates a successful connection to the
054     * remote repository. In case of a download, the requested remote resource exists and its size is given by
055     * {@link TransferResource#getContentLength()} if possible. This event may be fired multiple times for given
056     * transfer request if said transfer needs to be repeated (e.g. in response to an authentication challenge).
057     * 
058     * @param event The event details, must not be {@code null}.
059     * @throws TransferCancelledException If the transfer should be aborted.
060     */
061    void transferStarted( TransferEvent event )
062        throws TransferCancelledException;
063
064    /**
065     * Notifies the listener about some progress in the data transfer. This event may even be fired if actually zero
066     * bytes have been transferred since the last event, for instance to enable cancellation.
067     * 
068     * @param event The event details, must not be {@code null}.
069     * @throws TransferCancelledException If the transfer should be aborted.
070     */
071    void transferProgressed( TransferEvent event )
072        throws TransferCancelledException;
073
074    /**
075     * Notifies the listener that a checksum validation failed. {@link TransferEvent#getException()} will be of type
076     * {@link ChecksumFailureException} and can be used to query further details about the expected/actual checksums.
077     * 
078     * @param event The event details, must not be {@code null}.
079     * @throws TransferCancelledException If the transfer should be aborted.
080     */
081    void transferCorrupted( TransferEvent event )
082        throws TransferCancelledException;
083
084    /**
085     * Notifies the listener about the successful completion of a transfer. This event must be fired exactly once for a
086     * given transfer request unless said request failed.
087     * 
088     * @param event The event details, must not be {@code null}.
089     */
090    void transferSucceeded( TransferEvent event );
091
092    /**
093     * Notifies the listener about the unsuccessful termination of a transfer. {@link TransferEvent#getException()} will
094     * provide further information about the failure.
095     * 
096     * @param event The event details, must not be {@code null}.
097     */
098    void transferFailed( TransferEvent event );
099
100}