org.springframework.batch.item.support.IteratorItemReader.java Source code

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/*
 * Copyright 2006-2019 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.support;

import java.util.Iterator;

import org.springframework.batch.item.ItemReader;
import org.springframework.util.Assert;

/**
 * An {@link ItemReader} that pulls data from a {@link Iterator} or
 * {@link Iterable} using the constructors.
 * 
 * @author Juliusz Brzostek
 * @author Dave Syer
 * @author Mahmoud Ben Hassine
 */
public class IteratorItemReader<T> implements ItemReader<T> {

    /**
     * Internal iterator
     */
    private final Iterator<T> iterator;

    /**
     * Construct a new reader from this iterable (could be a collection), by
     * extracting an instance of {@link Iterator} from it.
     * 
     * @param iterable in instance of {@link Iterable}
     * 
     * @see Iterable#iterator()
     */
    public IteratorItemReader(Iterable<T> iterable) {
        Assert.notNull(iterable, "Iterable argument cannot be null!");
        this.iterator = iterable.iterator();
    }

    /**
     * Construct a new reader from this iterator directly.
     * @param iterator an instance of {@link Iterator}
     */
    public IteratorItemReader(Iterator<T> iterator) {
        Assert.notNull(iterator, "Iterator argument cannot be null!");
        this.iterator = iterator;
    }

    /**
     * Implementation of {@link ItemReader#read()} that just iterates over the
     * iterator provided.
     */
    @Override
    public T read() {
        if (iterator.hasNext())
            return iterator.next();
        else
            return null; // end of data
    }

}