trunk/camel-core/src/main/java/org/apache/camel/spi/SubUnitOfWorkCallback.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.camel.spi;

import org.apache.camel.Exchange;

/**
 * To allow unit of work for the {@link UnitOfWork} while processing a number of {@link Exchange}s.
 * <p/>
 * A sub unit of work is a way of implement sub-transactions in Camel routing.
 * This is needed by some EIPs where you can have sub routes such as the Splitter.
 * The Camel end user may want to indicate that the Splitter should act as a
 * <b>single combined</b> unit of work.
 * <p/>
 * To implement this, we use this {@link SubUnitOfWorkCallback}
 * which allows us to have the sub routes participate in a {@link SubUnitOfWork}
 * And then the outcome of the {@link SubUnitOfWork} will be a single atomic commit or rollback.
 * <p/>
 * When using a {@link SubUnitOfWork} we need to tap into the sub routes, and ensure they callback with the progress
 * of the sub {@link Exchange} being processed. For example the error handler, we need to tap into, and
 * ensure that any exhausted sub {@link Exchange} is propagated into the result of the {@link SubUnitOfWork}.
 * This {@link SubUnitOfWorkCallback} allows us to do that.
 *
 * @see SubUnitOfWork
 */
public interface SubUnitOfWorkCallback {

    /**
     * The exchange is exhausted, by a redeliverable error handler.
     *
     * @param exchange the exchange
     */
    void onExhausted(Exchange exchange);

    /**
     * The exchange is done.
     *
     * @param exchange the exchange.
     */
    void onDone(Exchange exchange);

}