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1   /*
2    * ModeShape (http://www.modeshape.org)
3    * See the COPYRIGHT.txt file distributed with this work for information
4    * regarding copyright ownership.  Some portions may be licensed
5    * to Red Hat, Inc. under one or more contributor license agreements.
6    * See the AUTHORS.txt file in the distribution for a full listing of 
7    * individual contributors.
8    *
9    * ModeShape is free software. Unless otherwise indicated, all code in ModeShape
10   * is licensed to you under the terms of the GNU Lesser General Public License as
11   * published by the Free Software Foundation; either version 2.1 of
12   * the License, or (at your option) any later version.
13   * 
14   * ModeShape is distributed in the hope that it will be useful,
15   * but WITHOUT ANY WARRANTY; without even the implied warranty of
16   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17   * Lesser General Public License for more details.
18   *
19   * You should have received a copy of the GNU Lesser General Public
20   * License along with this software; if not, write to the Free
21   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
22   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
23   */
24  package org.modeshape.graph.query.model;
25  
26  import net.jcip.annotations.Immutable;
27  import org.modeshape.common.util.CheckArg;
28  import org.modeshape.common.util.HashCode;
29  
30  /**
31   * A constraint that evaluates to true only when a named property exists on a node.
32   */
33  @Immutable
34  public class PropertyExistence implements Constraint {
35      private static final long serialVersionUID = 1L;
36  
37      private final SelectorName selectorName;
38      private final String propertyName;
39      private final int hc;
40  
41      /**
42       * Create a constraint requiring that a property exist on a node.
43       * 
44       * @param selectorName the name of the node selector
45       * @param propertyName the name of the property that must exist
46       */
47      public PropertyExistence( SelectorName selectorName,
48                                String propertyName ) {
49          CheckArg.isNotNull(selectorName, "selectorName");
50          CheckArg.isNotNull(propertyName, "propertyName");
51          this.selectorName = selectorName;
52          this.propertyName = propertyName;
53          this.hc = HashCode.compute(this.selectorName, this.propertyName);
54      }
55  
56      /**
57       * Get the name of the selector.
58       * 
59       * @return the selector name; never null
60       */
61      public final SelectorName selectorName() {
62          return selectorName;
63      }
64  
65      /**
66       * Get the name of the property.
67       * 
68       * @return the property name; never null
69       */
70      public final String propertyName() {
71          return propertyName;
72      }
73  
74      /**
75       * {@inheritDoc}
76       * 
77       * @see java.lang.Object#toString()
78       */
79      @Override
80      public String toString() {
81          return Visitors.readable(this);
82      }
83  
84      /**
85       * {@inheritDoc}
86       * 
87       * @see java.lang.Object#hashCode()
88       */
89      @Override
90      public int hashCode() {
91          return hc;
92      }
93  
94      /**
95       * {@inheritDoc}
96       * 
97       * @see java.lang.Object#equals(java.lang.Object)
98       */
99      @Override
100     public boolean equals( Object obj ) {
101         if (obj == this) return true;
102         if (obj instanceof PropertyExistence) {
103             PropertyExistence that = (PropertyExistence)obj;
104             if (this.hc != that.hc) return false;
105             return this.selectorName.equals(that.selectorName) && this.propertyName.equals(that.propertyName);
106         }
107         return false;
108     }
109 
110     /**
111      * {@inheritDoc}
112      * 
113      * @see org.modeshape.graph.query.model.Visitable#accept(org.modeshape.graph.query.model.Visitor)
114      */
115     public void accept( Visitor visitor ) {
116         visitor.visit(this);
117     }
118 }