View Javadoc

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  package org.springframework.batch.item.file.transform;
17  
18  import java.util.Collection;
19  import java.util.Map;
20  
21  /**
22   * {@link FieldExtractor} that just returns the original item. If the item is an
23   * array or collection it will be returned as is, otherwise it is wrapped in a
24   * single element array.
25   * 
26   * @author Dave Syer
27   * 
28   */
29  public class PassThroughFieldExtractor<T> implements FieldExtractor<T> {
30  
31  	/**
32  	 * Get an array of fields as close as possible to the input. The result
33  	 * depends on the type of the input:
34  	 * <ul>
35  	 * <li>A {@link FieldSet} or array will be returned as is</li>
36  	 * <li>For a Collection the <code>toArray()</code> method will be used</li>
37  	 * <li>For a Map the <code>values()</code> will be returned as an array</li>
38  	 * <li>Otherwise it is wrapped in a single element array.</li>
39  	 * </ul>
40  	 * Note that no attempt is made to sort the values, so passing in an
41  	 * unordered collection or map is probably a bad idea. Spring often gives
42  	 * you an ordered Map (e.g. if extracting data from a generic query using
43  	 * JDBC), so check the documentation for whatever is being used to generate
44  	 * the input.
45  	 * 
46  	 * @param item the object to convert
47  	 * @return an array of objects as close as possible to the original item
48  	 */
49      @Override
50  	public Object[] extract(T item) {
51  
52  		if (item.getClass().isArray()) {
53  			return (Object[]) item;
54  		}
55  
56  		if (item instanceof Collection<?>) {
57  			return ((Collection<?>) item).toArray();
58  		}
59  
60  		if (item instanceof Map<?, ?>) {
61  			return ((Map<?, ?>) item).values().toArray();
62  		}
63  
64  		if (item instanceof FieldSet) {
65  			return ((FieldSet) item).getValues();
66  		}
67  
68  		return new Object[] { item };
69  
70  	}
71  
72  }