LoadableDetachableGenericEntityDataProvider.java

package fr.openwide.core.wicket.more.model.optimization;

import java.io.Serializable;
import java.util.Iterator;
import java.util.List;

import fr.openwide.core.jpa.business.generic.model.GenericEntity;
import fr.openwide.core.wicket.more.markup.repeater.data.LoadableDetachableDataProvider;

public abstract class LoadableDetachableGenericEntityDataProvider<K extends Serializable & Comparable<K>, E extends GenericEntity<K, ?>>
		extends LoadableDetachableDataProvider<E>
		implements IGenericEntityDataProvider<K, E>{

	private static final long serialVersionUID = 996035545779191799L;

	private Long lastIdFirst;

	private Long lastIdCount;

	private List<K> lastIdList;

	protected abstract List<K> loadIdList(long first, long count);

	@Override
	public void detach() {
		super.detach();
		lastIdFirst = null;
		lastIdCount = null;
		lastIdList = null;
	}

	@Override
	public final Iterator<? extends K> idIterator(long first, long count) {
		long realCount = Math.min(count, size() - first);
		if (lastIdList != null && Long.valueOf(first).equals(lastIdFirst) && Long.valueOf(realCount).equals(lastIdCount)) {
			return lastIdList.iterator();
		} else {
			lastIdFirst = first;
			lastIdCount = realCount;
			lastIdList = loadIdList(first, count);
			return lastIdList.iterator();
		}
	}

}