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    1   /*
    2    * $Id: MergeIteratorFilter.java 471756 2006-11-06 15:01:43Z husted $
    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  package org.apache.struts2.util;
    22
    23  import java.util.ArrayList;
    24  import java.util.Iterator;
    25  import java.util.List;
    26
    27  import com.opensymphony.xwork2.Action;
    28
    29
    30  /***
    31   * A bean that takes several iterators and outputs the merge of them. Used by
    32   * MergeIteratorTag.
    33   *
    34   * @see org.apache.struts2.views.jsp.iterator.MergeIteratorTag
    35   * @see org.apache.struts2.components.MergeIterator
    36   */
    37  public class MergeIteratorFilter extends IteratorFilterSupport implements Iterator, Action {
    38
    39      List iterators = new ArrayList();
    40
    41      // Attributes ----------------------------------------------------
    42      List sources = new ArrayList();
    43      int idx = 0;
    44
    45
    46      // Public --------------------------------------------------------
    47      public void setSource(Object anIterator) {
    48          sources.add(anIterator);
    49      }
    50
    51      // Action implementation -----------------------------------------
    52      public String execute() {
    53          // Make source transformations
    54          for (int i = 0; i < sources.size(); i++) {
    55              Object source = sources.get(i);
    56              iterators.add(getIterator(source));
    57          }
    58
    59          return SUCCESS;
    60      }
    61
    62      // Iterator implementation ---------------------------------------
    63      public boolean hasNext() {
    64          while (iterators.size() > 0) {
    65              if (((Iterator) iterators.get(idx)).hasNext()) {
    66                  return true;
    67              } else {
    68                  iterators.remove(idx);
    69
    70                  if (iterators.size() > 0) {
    71                      idx = idx % iterators.size();
    72                  }
    73              }
    74          }
    75
    76          return false;
    77      }
    78
    79      public Object next() {
    80          try {
    81              return ((Iterator) iterators.get(idx)).next();
    82          } finally {
    83              idx = (idx + 1) % iterators.size();
    84          }
    85      }
    86
    87      public void remove() {
    88          throw new UnsupportedOperationException("Remove is not supported in MergeIteratorFilter.");
    89      }
    90  }