org.springframework.batch.jsr.item.CheckpointSupport.java Source code

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Here is the source code for org.springframework.batch.jsr.item.CheckpointSupport.java

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/*
 * 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);
        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
     */
    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
     */
    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
     */
    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;
    }

}