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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.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;
}