1 /*
2 * $Id: MergeIteratorFilter.java 651946 2008-04-27 13:41:38Z apetrelli $
3 *
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 package org.apache.struts2.util;
23
24 import java.util.ArrayList;
25 import java.util.Iterator;
26 import java.util.List;
27
28 import com.opensymphony.xwork2.Action;
29
30
31 /***
32 * A bean that takes several iterators and outputs the merge of them. Used by
33 * MergeIteratorTag.
34 *
35 * @see org.apache.struts2.views.jsp.iterator.MergeIteratorTag
36 * @see org.apache.struts2.components.MergeIterator
37 */
38 public class MergeIteratorFilter extends IteratorFilterSupport implements Iterator, Action {
39
40 List iterators = new ArrayList();
41
42 // Attributes ----------------------------------------------------
43 List sources = new ArrayList();
44 int idx = 0;
45
46
47 // Public --------------------------------------------------------
48 public void setSource(Object anIterator) {
49 sources.add(anIterator);
50 }
51
52 // Action implementation -----------------------------------------
53 public String execute() {
54 // Make source transformations
55 for (int i = 0; i < sources.size(); i++) {
56 Object source = sources.get(i);
57 iterators.add(getIterator(source));
58 }
59
60 return SUCCESS;
61 }
62
63 // Iterator implementation ---------------------------------------
64 public boolean hasNext() {
65 while (iterators.size() > 0) {
66 if (((Iterator) iterators.get(idx)).hasNext()) {
67 return true;
68 } else {
69 iterators.remove(idx);
70
71 if (iterators.size() > 0) {
72 idx = idx % iterators.size();
73 }
74 }
75 }
76
77 return false;
78 }
79
80 public Object next() {
81 try {
82 return ((Iterator) iterators.get(idx)).next();
83 } finally {
84 idx = (idx + 1) % iterators.size();
85 }
86 }
87
88 public void remove() {
89 throw new UnsupportedOperationException("Remove is not supported in MergeIteratorFilter.");
90 }
91 }