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