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1   /*
2    * Copyright 2012-2013 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.amqp;
18  
19  import org.springframework.amqp.core.AmqpTemplate;
20  import org.springframework.amqp.core.Message;
21  import org.springframework.batch.item.ItemReader;
22  import org.springframework.util.Assert;
23  
24  /**
25   * <p>
26   * AMQP {@link ItemReader} implementation using an {@link AmqpTemplate} to
27   * receive and/or convert messages.
28   * </p>
29   *
30   * @author Chris Schaefer
31   */
32  public class AmqpItemReader<T> implements ItemReader<T> {
33  	private final AmqpTemplate amqpTemplate;
34  	private Class<? extends T> itemType;
35  
36  	public AmqpItemReader(final AmqpTemplate amqpTemplate) {
37  		Assert.notNull(amqpTemplate, "AmpqTemplate must not be null");
38  
39  		this.amqpTemplate = amqpTemplate;
40  	}
41  
42  	@Override
43  	@SuppressWarnings("unchecked")
44  	public T read() {
45  		if (itemType != null && itemType.isAssignableFrom(Message.class)) {
46  			return (T) amqpTemplate.receive();
47  		}
48  
49  		Object result = amqpTemplate.receiveAndConvert();
50  
51  		if (itemType != null && result != null) {
52  			Assert.state(itemType.isAssignableFrom(result.getClass()),
53  					"Received message payload of wrong type: expected [" + itemType + "]");
54  		}
55  
56  		return (T) result;
57  	}
58  
59  	public void setItemType(Class<? extends T> itemType) {
60  		Assert.notNull(itemType, "Item type cannot be null");
61  		this.itemType = itemType;
62  	}
63  }