View Javadoc

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  }