org.opensourcebank.batch.reader.HazelcastMapItemReader.java Source code

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Here is the source code for org.opensourcebank.batch.reader.HazelcastMapItemReader.java

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/*
 * Copyright 2011 Anatoly Polinsky
 *
 *    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.opensourcebank.batch.reader;

import com.hazelcast.core.Hazelcast;
import org.apache.log4j.Logger;
import org.springframework.batch.item.*;
import org.springframework.beans.factory.InitializingBean;

import java.util.List;
import java.util.Map;

/**
 * <p>An {@link ItemReader} that given a map name, pulls data item by item from a Hazelcast (distributed) Map.</p>
 *
 * <p>This reader makes two assumptions:
 *
 *                1. Keys are {@link Long},
 *                2. Keys are sequential ( 4,5,6,7,8,9,10,11, etc.. )</p>
 *
 * @author anatoly.polinsky
 */
public class HazelcastMapItemReader<T> implements ItemReader<T>, ItemStream, InitializingBean {

    private static final String CURRENT_ITEM_ID = "current.item.id";
    private static final Logger logger = Logger.getLogger(HazelcastMapItemReader.class);

    Map<Long, T> itemMap;
    String mapName;

    long fromId;
    long toId;

    long currentItemId;

    public T read() throws Exception {

        if (currentItemId <= toId) {
            return itemMap.get(currentItemId++);
        }

        return null;
    }

    public void open(ExecutionContext executionContext) throws ItemStreamException {

        // staring Hazelcast to have this node join the cluster
        // and getting a reference to an items map
        itemMap = Hazelcast.getMap(mapName);

        // possibly restarted, but all items were completed / evicted by another node
        // or just a wrong map name
        if (itemMap.size() == 0) {
            logger.warn("Map [ " + mapName + " ] is empty, no items to read");
        }

        // is this step restarted?
        if (executionContext.containsKey(CURRENT_ITEM_ID)) {
            currentItemId = new Long(executionContext.getLong(CURRENT_ITEM_ID)).intValue();
        } else {
            currentItemId = fromId;
        }
    }

    public void update(ExecutionContext executionContext) throws ItemStreamException {

        // save the current item ID to make this step restartable
        executionContext.putLong(CURRENT_ITEM_ID, new Long(currentItemId).longValue());
    }

    public void close() throws ItemStreamException {
    }

    public void afterPropertiesSet() throws Exception {
        if (("".equals(mapName)) || (mapName == null)) {
            throw new IllegalArgumentException(this.getClass().getSimpleName() + ": 'mapName' must be set");
        }
        if ((fromId >= 0) && (toId > 0)) {
            if (fromId >= toId) {
                throw new IllegalArgumentException(
                        this.getClass().getSimpleName() + ": 'fromId' must be less than 'toId'");
            }
        } else {
            throw new IllegalArgumentException(this.getClass().getSimpleName()
                    + ": 'fromId' and 'toId' must be set, and 'fromId' should be less than 'toId'");
        }
    }

    // public accessors

    public String getMapName() {
        return mapName;
    }

    public void setMapName(String mapName) {
        this.mapName = mapName;
    }

    public long getFromId() {
        return fromId;
    }

    public void setFromId(long fromId) {
        this.fromId = fromId;
    }

    public long getToId() {
        return toId;
    }

    public void setToId(long toId) {
        this.toId = toId;
    }
}