PruningElementStack xref

View Javadoc

    1   /*
    2    * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
    3    *
    4    * This software is open source.
    5    * See the bottom of this file for the licence.
    6    */
    7
    8   package org.dom4j.io;
    9
    10  import org.dom4j.Element;
    11  import org.dom4j.ElementHandler;
    12
    13  /***
    14   * <p>
    15   * <code>PruningElementStack</code> is a stack of {@link Element}instances
    16   * which will prune the tree when a path expression is reached. This is useful
    17   * for parsing very large documents where children of the root element can be
    18   * processed individually rather than keeping them all in memory at the same
    19   * time.
    20   * </p>
    21   *
    22   * @author <a href="mailto:james.strachan@metastuff.com">James Strachan </a>
    23   * @version $Revision: 1.11 $
    24   */
    25  class PruningElementStack extends ElementStack {
    26      /*** ElementHandler to call when pruning occurs */
    27      private ElementHandler elementHandler;
    28
    29      /***
    30       * the element name path which denotes the node to remove from its parent
    31       * when it is complete (i.e. when it is popped from the stack). The first
    32       * entry in the path will be a child of the root node
    33       */
    34      private String[] path;
    35
    36      /***
    37       * The level at which a path match can occur. We match when we have popped
    38       * the selected node so the and the lastElementIndex points to its parent so
    39       * this value should be path.length - 2
    40       */
    41      private int matchingElementIndex;
    42
    43      public PruningElementStack(String[] path, ElementHandler elementHandler) {
    44          this.path = path;
    45          this.elementHandler = elementHandler;
    46          checkPath();
    47      }
    48
    49      public PruningElementStack(String[] path, ElementHandler elementHandler,
    50              int defaultCapacity) {
    51          super(defaultCapacity);
    52          this.path = path;
    53          this.elementHandler = elementHandler;
    54          checkPath();
    55      }
    56
    57      public Element popElement() {
    58          Element answer = super.popElement();
    59
    60          if ((lastElementIndex == matchingElementIndex)
    61                  && (lastElementIndex >= 0)) {
    62              // we are popping the correct level in the tree
    63              // lets check if the path fits
    64              //
    65              // NOTE: this is an inefficient way of doing it - we could
    66              // maintain a history of which parts matched?
    67              if (validElement(answer, lastElementIndex + 1)) {
    68                  Element parent = null;
    69
    70                  for (int i = 0; i <= lastElementIndex; i++) {
    71                      parent = stack[i];
    72
    73                      if (!validElement(parent, i)) {
    74                          parent = null;
    75
    76                          break;
    77                      }
    78                  }
    79
    80                  if (parent != null) {
    81                      pathMatches(parent, answer);
    82                  }
    83              }
    84          }
    85
    86          return answer;
    87      }
    88
    89      protected void pathMatches(Element parent, Element selectedNode) {
    90          elementHandler.onEnd(this);
    91          parent.remove(selectedNode);
    92      }
    93
    94      protected boolean validElement(Element element, int index) {
    95          String requiredName = path[index];
    96          String name = element.getName();
    97
    98          if (requiredName == name) {
    99              return true;
    100         }
    101
    102         if ((requiredName != null) && (name != null)) {
    103             return requiredName.equals(name);
    104         }
    105
    106         return false;
    107     }
    108
    109     private void checkPath() {
    110         if (path.length < 2) {
    111             throw new RuntimeException("Invalid path of length: " + path.length
    112                     + " it must be greater than 2");
    113         }
    114
    115         matchingElementIndex = path.length - 2;
    116     }
    117 }
    118
    119 /*
    120  * Redistribution and use of this software and associated documentation
    121  * ("Software"), with or without modification, are permitted provided that the
    122  * following conditions are met:
    123  *
    124  * 1. Redistributions of source code must retain copyright statements and
    125  * notices. Redistributions must also contain a copy of this document.
    126  *
    127  * 2. Redistributions in binary form must reproduce the above copyright notice,
    128  * this list of conditions and the following disclaimer in the documentation
    129  * and/or other materials provided with the distribution.
    130  *
    131  * 3. The name "DOM4J" must not be used to endorse or promote products derived
    132  * from this Software without prior written permission of MetaStuff, Ltd. For
    133  * written permission, please contact dom4j-info@metastuff.com.
    134  *
    135  * 4. Products derived from this Software may not be called "DOM4J" nor may
    136  * "DOM4J" appear in their names without prior written permission of MetaStuff,
    137  * Ltd. DOM4J is a registered trademark of MetaStuff, Ltd.
    138  *
    139  * 5. Due credit should be given to the DOM4J Project - http://www.dom4j.org
    140  *
    141  * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS ``AS IS'' AND
    142  * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    143  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    144  * ARE DISCLAIMED. IN NO EVENT SHALL METASTUFF, LTD. OR ITS CONTRIBUTORS BE
    145  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    146  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    147  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    148  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    149  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    150  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    151  * POSSIBILITY OF SUCH DAMAGE.
    152  *
    153  * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
    154  */