MyNounLoader.java

package com.hazelcast.samples.spring.data.migration;

import com.hazelcast.core.MapLoader;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

/**
 * Connect a Hazelcast server to an RDBMS, so a Java {@code map} can be populated
 * on demand from a database table.
 *
 * <u><b>MIGRATION PATH</b></u>
 * <ol>
 * <li>Add this class.</li>
 * </ol>
 */
@Component
@Slf4j
public class MyNounLoader implements ApplicationContextAware, MapLoader<Integer, Noun> {

    private static NounJPARepository nounJPARepository;

    /**
     * Load one record using its key.
     *
     * @return Null if not found
     */
    @Override
    public Noun load(Integer key) {
        log.info("load({})", key);
        return nounJPARepository.findOne(key);
    }

    /**
     * Given this member a subset of keys to pre-load.
     *
     * @return Records for the given keys
     */
    @Override
    public Map<Integer, Noun> loadAll(Collection<Integer> keys) {
        Map<Integer, Noun> result = new HashMap<>();
        for (Integer key : keys) {
            Noun noun = this.load(key);
            if (noun != null) {
                result.put(key, noun);
            }
        }
        return result;
    }

    /**
     * Select all keys that should be pre-loaded. Run on one member in the cluster.
     *
     * @return All keys
     */
    @Override
    public Iterable<Integer> loadAllKeys() {
        return nounJPARepository.findAllId();
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        nounJPARepository = applicationContext.getBean(NounJPARepository.class);
    }
}