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  
17  package org.springframework.batch.item.file.transform;
18  
19  import java.util.Collection;
20  
21  
22  /**
23   * An implementation of {@link LineAggregator} that concatenates a collection of
24   * items of a common type with the system line separator.
25   * 
26   * @author Dave Syer
27   * 
28   */
29  public class RecursiveCollectionLineAggregator<T> implements LineAggregator<Collection<T>> {
30  
31  	private static final String LINE_SEPARATOR = System.getProperty("line.separator");
32  
33  	private LineAggregator<T> delegate = new PassThroughLineAggregator<T>();
34  
35  	/**
36  	 * Public setter for the {@link LineAggregator} to use on single items, that
37  	 * are not Strings. This can be used to strategise the conversion of
38  	 * collection and array elements to a String.<br/>
39  	 * 
40  	 * @param delegate the line aggregator to set. Defaults to a pass through.
41  	 */
42  	public void setDelegate(LineAggregator<T> delegate) {
43  		this.delegate = delegate;
44  	}
45  
46  	/*
47  	 * (non-Javadoc)
48  	 * @see org.springframework.batch.item.file.transform.LineAggregator#aggregate(java.lang.Object)
49  	 */
50      @Override
51  	public String aggregate(Collection<T> items) {
52  		StringBuilder builder = new StringBuilder();
53  		for (T value : items) {
54  			builder.append(delegate.aggregate(value) + LINE_SEPARATOR);
55  		}
56  		return builder.delete(builder.length()-LINE_SEPARATOR.length(),builder.length()).toString();
57  	}
58  
59  }