001/*
002 * Licensed to DuraSpace under one or more contributor license agreements.
003 * See the NOTICE file distributed with this work for additional information
004 * regarding copyright ownership.
005 *
006 * DuraSpace licenses this file to you under the Apache License,
007 * Version 2.0 (the "License"); you may not use this file except in
008 * compliance 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, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.fcrepo.kernel.api.observer;
020
021import org.fcrepo.kernel.api.Transaction;
022import org.fcrepo.kernel.api.identifiers.FedoraId;
023import org.fcrepo.kernel.api.operations.ResourceOperation;
024
025/**
026 * Accumulates events for changes made to resources, grouped by transaction. The events are not emitted until after the
027 * transaction has been committed. If a transaction is rolled back, {@link #clearEvents} MUST be called to release the
028 * stored events.
029 *
030 * @author pwinckles
031 */
032public interface EventAccumulator {
033
034    /**
035     * Registers a new event to a transaction.
036     *
037     * @param transaction the transaction
038     * @param fedoraId the id of the affected resource
039     * @param operation the operation affecting the resource
040     */
041    void recordEventForOperation(Transaction transaction, FedoraId fedoraId, ResourceOperation operation);
042
043    /**
044     * Emits all of the events that were accumulated within the transaction. Multiple events affecting the same resource
045     * are combined into a single event.
046     *
047     * <p>This method SHOULD NOT throw an exception if an event fails to be emitted. It should always attempt to emit
048     * all events accumulated within a transaction.
049     *
050     * @param transaction the transaction
051     * @param baseUrl the baseUrl of the requests
052     * @param userAgent the user-agent of the user making the requests
053     */
054    void emitEvents(Transaction transaction, String baseUrl, String userAgent);
055
056    /**
057     * Removes all of a transaction's accumulated events without emitting them. This must be called when a transaction
058     * is rolled back.
059     *
060     * @param transaction the id of the transaction
061     */
062    void clearEvents(Transaction transaction);
063
064}