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The Spring Batch Infrastructure is a set of low-level components, interfaces and tools for batch processing applications and optimisations.

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/*
 * Copyright 2002-2022 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
 *
 * https://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.item;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.convert.converter.Converter;
import org.springframework.util.Assert;

/**
 * A base class to implement any {@link ItemWriter} that writes to a key value store using
 * a {@link Converter} to derive a key from an item
 *
 * @author David Turanski
 * @author Mahmoud Ben Hassine
 * @since 2.2
 *
 */
public abstract class KeyValueItemWriter implements ItemWriter, InitializingBean {

	protected Converter itemKeyMapper;

	protected boolean delete;

	/*
	 * (non-Javadoc)
	 *
	 * @see org.springframework.batch.item.ItemWriter#write(java.util.List)
	 */
	@Override
	public void write(Chunk items) throws Exception {
		if (items == null) {
			return;
		}
		for (V item : items) {
			K key = itemKeyMapper.convert(item);
			writeKeyValue(key, item);
		}
		flush();
	}

	/**
	 * Flush items to the key/value store.
	 * @throws Exception if unable to flush items
	 */
	protected void flush() throws Exception {
	}

	/**
	 * Subclasses implement this method to write each item to key value store
	 * @param key the key
	 * @param value the item
	 */
	protected abstract void writeKeyValue(K key, V value);

	/**
	 * afterPropertiesSet() hook
	 */
	protected abstract void init();

	/**
	 * Set the {@link Converter} to use to derive the key from the item
	 * @param itemKeyMapper the {@link Converter} used to derive a key from an item.
	 */
	public void setItemKeyMapper(Converter itemKeyMapper) {
		this.itemKeyMapper = itemKeyMapper;
	}

	/**
	 * Sets the delete flag to have the item writer perform deletes
	 * @param delete if true {@link ItemWriter} will perform deletes, if false not to
	 * perform deletes.
	 */
	public void setDelete(boolean delete) {
		this.delete = delete;
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
	 */
	@Override
	public void afterPropertiesSet() throws Exception {
		Assert.state(itemKeyMapper != null, "itemKeyMapper requires a Converter type.");
		init();
	}

}