javax.batch.api.chunk.ItemReader Maven / Gradle / Ivy
/*
* 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.chunk;
import java.io.Serializable;
/**
*
* ItemReader defines the batch artifact that reads items for chunk processing.
*
*/
public interface ItemReader {
/**
* The open method prepares the reader to read items.
*
* The input parameter represents the last checkpoint for this reader in a
* given job instance. The checkpoint data is defined by this reader and is
* provided by the checkpointInfo method. The checkpoint data provides the
* reader whatever information it needs to resume reading items upon
* restart. A checkpoint value of null is passed upon initial start.
*
* @param checkpoint
* specifies the last checkpoint
* @throws Exception
* is thrown for any errors.
*/
public void open(Serializable checkpoint) throws Exception;
/**
* The close method marks the end of use of the ItemReader. The reader is
* free to do any cleanup necessary.
*
* @throws Exception
* is thrown for any errors.
*/
public void close() throws Exception;
/**
* The readItem method returns the next item for chunk processing. It
* returns null to indicate no more items, which also means the current
* chunk will be committed and the step will end.
*
* @return next item or null
* @throws Exception
* is thrown for any errors.
*/
public Object readItem() throws Exception;
/**
* The checkpointInfo method returns the current checkpoint data for this
* reader. It is called before a chunk checkpoint is committed.
*
* @return checkpoint data
* @throws Exception
* is thrown for any errors.
*/
public Serializable checkpointInfo() throws Exception;
}