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1   /*
2    * Copyright 2006-2007 the original author or authors.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.batch.item.support;
18  
19  import java.util.Iterator;
20  
21  import org.springframework.batch.item.ItemReader;
22  import org.springframework.batch.item.ParseException;
23  import org.springframework.batch.item.UnexpectedInputException;
24  import org.springframework.util.Assert;
25  
26  /**
27   * An {@link ItemReader} that pulls data from a {@link Iterator} or
28   * {@link Iterable} using the constructors.
29   * 
30   * @author Juliusz Brzostek
31   * @author Dave Syer
32   */
33  public class IteratorItemReader<T> implements ItemReader<T> {
34  
35  	/**
36  	 * Internal iterator
37  	 */
38  	private final Iterator<T> iterator;
39  
40  	/**
41  	 * Construct a new reader from this iterable (could be a collection), by
42  	 * extracting an instance of {@link Iterator} from it.
43  	 * 
44  	 * @param iterable in instance of {@link Iterable}
45  	 * 
46  	 * @see Iterable#iterator()
47  	 */
48  	public IteratorItemReader(Iterable<T> iterable) {
49  		Assert.notNull(iterable, "Iterable argument cannot be null!");
50  		this.iterator = iterable.iterator();
51  	}
52  
53  	/**
54  	 * Construct a new reader from this iterator directly.
55  	 * @param iterator an instance of {@link Iterator}
56  	 */
57  	public IteratorItemReader(Iterator<T> iterator) {
58  		Assert.notNull(iterator, "Iterator argument cannot be null!");
59  		this.iterator = iterator;
60  	}
61  
62  	/**
63  	 * Implementation of {@link ItemReader#read()} that just iterates over the
64  	 * iterator provided.
65  	 */
66      @Override
67  	public T read() throws Exception, UnexpectedInputException, ParseException {
68  		if (iterator.hasNext())
69  			return iterator.next();
70  		else
71  			return null; // end of data
72  	}
73  
74  }