001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.spi;
018
019import org.apache.camel.Exchange;
020
021/**
022 * To allow unit of work for the {@link UnitOfWork} while processing a number of {@link Exchange}s.
023 * <p/>
024 * A sub unit of work is a way of implement sub-transactions in Camel routing.
025 * This is needed by some EIPs where you can have sub routes such as the Splitter.
026 * The Camel end user may want to indicate that the Splitter should act as a
027 * <b>single combined</b> unit of work.
028 * <p/>
029 * To implement this, we use this {@link SubUnitOfWorkCallback}
030 * which allows us to have the sub routes participate in a {@link SubUnitOfWork}
031 * And then the outcome of the {@link SubUnitOfWork} will be a single atomic commit or rollback.
032 * <p/>
033 * When using a {@link SubUnitOfWork} we need to tap into the sub routes, and ensure they callback with the progress
034 * of the sub {@link Exchange} being processed. For example the error handler, we need to tap into, and
035 * ensure that any exhausted sub {@link Exchange} is propagated into the result of the {@link SubUnitOfWork}.
036 * This {@link SubUnitOfWorkCallback} allows us to do that.
037 *
038 * @see SubUnitOfWork
039 */
040public interface SubUnitOfWorkCallback {
041
042    /**
043     * The exchange is exhausted, by a redeliverable error handler.
044     *
045     * @param exchange the exchange
046     */
047    void onExhausted(Exchange exchange);
048
049    /**
050     * The exchange is done.
051     *
052     * @param exchange the exchange.
053     */
054    void onDone(Exchange exchange);
055
056}