javax.batch.api.partition.PartitionReducer Maven / Gradle / Ivy

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/*
 * Copyright 2012 International Business Machines Corp.
 * 
 * See the NOTICE file distributed with this work for additional information
 * regarding copyright ownership. Licensed 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 javax.batch.api.partition;

/**
 * PartitionReducer provides unit of work demarcation across partitions. It is
 * not a JTA transaction; no resources are enlisted. Rather, it provides
 * transactional flow semantics to facilitate finalizing merge or compensation
 * logic.
 * 
 */
public interface PartitionReducer {
    public enum PartitionStatus {
        COMMIT, ROLLBACK
    }

    /**
     * The beginPartitionedStep method receives control at the start of
     * partition processing. It receives control before the PartitionMapper 81
     * is invoked and before any partitions are started.
     * 
     * @throws Exception
     *             is thrown if an error occurs.
     */
    public void beginPartitionedStep() throws Exception;

    /**
     * The beforePartitionedStepCompletion method receives control at the end of
     * partitioned step processing. It receives control after all partitions
     * have completed. It does not receive control if the PartitionReducer is
     * rolling back.
     * 
     * @throws Exception
     *             is thrown if an error occurs.
     */
    public void beforePartitionedStepCompletion() throws Exception;

    /**
     * The rollbackPartitionedStep method receives control if the runtime is
     * rolling back a partitioned step. Any partition threads still running are
     * allowed to complete before this method is invoked. This method receives
     * control if any of the following conditions are true:
     * 
     * 

     * One or more partitions end with a Batch Status of STOPPED or FAILED.
     * Any of the following partitioned step callbacks throw an exception:
     * 
     * PartitionMapper
     * PartitionReducer
     * PartitionCollector
     * PartitionAnalyzer
     * 
     * A job with partitioned steps is restarted.
 
     * 
     * @throws Exception
     *             is thrown if an error occurs.
     */
    public void rollbackPartitionedStep() throws Exception;

    /**
     * The afterPartitionedStepCompletion method receives control at the end of
     * a partition processing. It receives a status value that identifies the
     * outcome of the partition processing. The status string value is either
     * "COMMIT" or "ROLLBACK".
     * 
     * @param status
     *            specifies the outcome of the partitioned step. Values are
     *            "COMMIT" or "ROLLBACK".
     * @throws Exception
     *             is thrown if an error occurs.
     */
    public void afterPartitionedStepCompletion(PartitionStatus status) throws Exception;
}