/*
* Copyright 2013 the original author or authors.
*
* 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 org.springframework.batch.jsr.item;
import java.io.Serializable;
import javax.batch.api.chunk.ItemReader;
import javax.batch.api.chunk.ItemWriter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.item.ExecutionContext;
import org.springframework.batch.item.ItemStreamException;
import org.springframework.batch.item.ItemStreamSupport;
import org.springframework.util.Assert;
import org.springframework.util.SerializationUtils;
/**
* Provides support for JSR-352 checkpointing. Checkpoint objects are copied prior
* to being added to the {@link ExecutionContext} for persistence by the framework.
* If the checkpoint object cannot be copied and further changes occur to the same
* instance, side effects may occur. In cases like this, it is recommended that a
* copy of the object being acted upon in the reader/writer is returned via the
* {@link ItemReader#checkpointInfo()} or {@link ItemWriter#checkpointInfo()} calls.
*
* @author Michael Minella
* @since 3.0
*/
public abstract class CheckpointSupport extends ItemStreamSupport{
private final Log logger = LogFactory.getLog(this.getClass());
private final String checkpointKey;
/**
* @param checkpointKey key to store the checkpoint object with in the {@link ExecutionContext}
*/
public CheckpointSupport(String checkpointKey) {
Assert.hasText(checkpointKey, "checkpointKey is required");
this.checkpointKey = checkpointKey;
}
/* (non-Javadoc)
* @see org.springframework.batch.item.ItemStreamSupport#open(org.springframework.batch.item.ExecutionContext)
*/
@Override
public void open(ExecutionContext executionContext)
throws ItemStreamException {
try {
String executionContextKey = getExecutionContextKey(checkpointKey);
Serializable checkpoint = (Serializable) executionContext.get(executionContextKey);
doOpen(checkpoint);
} catch (Exception e) {
throw new ItemStreamException(e);
}
}
/**
* Used to open a batch artifact with previously saved checkpoint information.
*
* @param checkpoint previously saved checkpoint object
* @throws Exception thrown by the implementation
*/
protected abstract void doOpen(Serializable checkpoint) throws Exception;
/* (non-Javadoc)
* @see org.springframework.batch.item.ItemStreamSupport#update(org.springframework.batch.item.ExecutionContext)
*/
@Override
public void update(ExecutionContext executionContext)
throws ItemStreamException {
try {
executionContext.put(getExecutionContextKey(checkpointKey), deepCopy(doCheckpoint()));
} catch (Exception e) {
throw new ItemStreamException(e);
}
}
/**
* Used to provide a {@link Serializable} representing the current state of the
* batch artifact.
*
* @return the current state of the batch artifact
* @throws Exception thrown by the implementation
*/
protected abstract Serializable doCheckpoint() throws Exception;
/* (non-Javadoc)
* @see org.springframework.batch.item.ItemStreamSupport#close()
*/
@Override
public void close() throws ItemStreamException {
try {
doClose();
} catch (Exception e) {
throw new ItemStreamException(e);
}
}
/**
* Used to close the underlying batch artifact
*
* @throws Exception thrown by the underlying implementation
*/
protected abstract void doClose() throws Exception;
private Object deepCopy(Serializable orig) {
Object obj = orig;
try {
obj = SerializationUtils.deserialize(SerializationUtils.serialize(orig));
} catch (Exception e) {
logger.warn("Unable to copy checkpoint object. Updating the instance passed may cause side effects");
}
return obj;
}
}