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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/expr/DefaultUnionExpr.java,v 1.12 2005/04/03 01:30:10 elharo Exp $
3    * $Revision: 1.12 $
4    * $Date: 2005/04/03 01:30:10 $
5    *
6    * ====================================================================
7    *
8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9    * All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions
13   * are met:
14   * 
15   * 1. Redistributions of source code must retain the above copyright
16   *    notice, this list of conditions, and the following disclaimer.
17   *
18   * 2. Redistributions in binary form must reproduce the above copyright
19   *    notice, this list of conditions, and the disclaimer that follows 
20   *    these conditions in the documentation and/or other materials 
21   *    provided with the distribution.
22   *
23   * 3. The name "Jaxen" must not be used to endorse or promote products
24   *    derived from this software without prior written permission.  For
25   *    written permission, please contact license@jaxen.org.
26   * 
27   * 4. Products derived from this software may not be called "Jaxen", nor
28   *    may "Jaxen" appear in their name, without prior written permission
29   *    from the Jaxen Project Management (pm@jaxen.org).
30   * 
31   * In addition, we request (but do not require) that you include in the 
32   * end-user documentation provided with the redistribution and/or in the 
33   * software itself an acknowledgement equivalent to the following:
34   *     "This product includes software developed by the
35   *      Jaxen Project (http://www.jaxen.org/)."
36   * Alternatively, the acknowledgment may be graphical using the logos 
37   * available at http://www.jaxen.org/
38   *
39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50   * SUCH DAMAGE.
51   *
52   * ====================================================================
53   * This software consists of voluntary contributions made by many 
54   * individuals on behalf of the Jaxen Project and was originally 
55   * created by bob mcwhirter <bob@werken.com> and 
56   * James Strachan <jstrachan@apache.org>.  For more information on the 
57   * Jaxen Project, please see <http://www.jaxen.org/>.
58   * 
59   * $Id: DefaultUnionExpr.java,v 1.12 2005/04/03 01:30:10 elharo Exp $
60   */
61  
62  
63  
64  package org.jaxen.expr;
65  
66  import java.util.ArrayList;
67  import java.util.Collections;
68  import java.util.HashSet;
69  import java.util.Iterator;
70  import java.util.List;
71  import java.util.Set;
72  import org.jaxen.Context;
73  import org.jaxen.JaxenException;
74  import org.jaxen.XPathSyntaxException;
75  
76  public class DefaultUnionExpr extends DefaultBinaryExpr implements UnionExpr
77  {
78      public DefaultUnionExpr(Expr lhs,
79                              Expr rhs)
80      {
81          super( lhs,
82                 rhs );
83      }
84  
85      public String getOperator()
86      {
87          return "|";
88      }
89  
90      public String toString()
91      {
92          return "[(DefaultUnionExpr): " + getLHS() + ", " + getRHS() + "]";
93      }
94  
95      public Object evaluate(Context context) throws JaxenException
96      {
97          List results = new ArrayList();
98  
99          try {
100             List lhsResults = (List) getLHS().evaluate( context );
101             List rhsResults = (List) getRHS().evaluate( context );
102     
103             Set unique = new HashSet();
104     
105             results.addAll( lhsResults );
106             unique.addAll( lhsResults );
107     
108             Iterator rhsIter = rhsResults.iterator();
109     
110             while ( rhsIter.hasNext() )
111             {
112                 Object each = rhsIter.next();
113     
114                 if ( ! unique.contains( each ) )
115                 {
116                     results.add( each );
117                     unique.add( each );
118                 }
119             }
120             
121             Collections.sort(results, new NodeComparator(context.getNavigator()));
122     
123             return results;
124         }
125         catch (ClassCastException e) {
126             throw new XPathSyntaxException(this.getText(), context.getPosition(), "Unions are only allowed over node-sets");
127         }
128     }
129     
130     public void accept(Visitor visitor)
131     {
132         visitor.visit(this);
133     }
134     
135 }
136