1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.directory.api.ldap.model.filter;
21
22
23 import java.text.ParseException;
24 import java.util.Comparator;
25 import java.util.List;
26 import java.util.Set;
27 import java.util.TreeSet;
28
29 import org.apache.directory.api.ldap.model.schema.SchemaManager;
30
31
32 /**
33 * Visitor which traverses a filter tree while normalizing the branch node
34 * order. Filter expressions can change the order of expressions in branch nodes
35 * without effecting the logical meaning of the expression. This visitor orders
36 * the children of expression tree branch nodes consistantly. It is really
37 * useful for comparing expression trees which may be altered for performance or
38 * altered because of codec idiosyncracies: for example the SNACC4J codec uses a
39 * hashmap to store expressions in a sequence which rearranges the order of
40 * children based on object hashcodes. We need this visitor to remove such
41 * inconsitancies in order hence normalizing the branch node's child order.
42 *
43 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
44 */
45 public class BranchNormalizedVisitor implements FilterVisitor
46 {
47 /**
48 * {@inheritDoc}
49 */
50 @Override
51 public Object visit( ExprNode node )
52 {
53 if ( !( node instanceof BranchNode ) )
54 {
55 return null;
56 }
57
58 BranchNode branch = ( BranchNode ) node;
59
60 Comparator<ExprNode> nodeComparator = new NodeComparator();
61
62 Set<ExprNode> set = new TreeSet<>( nodeComparator );
63
64 List<ExprNode> children = branch.getChildren();
65
66 for ( ExprNode child : branch.getChildren() )
67 {
68 if ( !child.isLeaf() )
69 {
70 ExprNode newChild = ( ExprNode ) visit( child );
71
72 if ( newChild != null )
73 {
74 set.add( newChild );
75 }
76 }
77 else
78 {
79 set.add( child );
80 }
81 }
82
83 children.clear();
84
85 children.addAll( set );
86
87 return branch;
88 }
89
90
91 /**
92 * {@inheritDoc}
93 */
94 @Override
95 public boolean canVisit( ExprNode node )
96 {
97 return node instanceof BranchNode;
98 }
99
100
101 /**
102 * {@inheritDoc}
103 */
104 @Override
105 public boolean isPrefix()
106 {
107 return false;
108 }
109
110
111 /**
112 * {@inheritDoc}
113 */
114 @Override
115 public List<ExprNode> getOrder( BranchNode node, List<ExprNode> children )
116 {
117 return children;
118 }
119
120
121 /**
122 * Normalizes a filter expression to a canonical representation while
123 * retaining logical meaning of the expression.
124 *
125 * @param schemaManager The SchemaManager
126 * @param filter the filter to normalize
127 * @return the normalized version of the filter
128 * @throws java.text.ParseException if the filter is malformed
129 */
130 public static String getNormalizedFilter( SchemaManager schemaManager, String filter ) throws ParseException
131 {
132 ExprNode originalNode = FilterParser.parse( schemaManager, filter );
133
134 return getNormalizedFilter( originalNode );
135 }
136
137
138 /**
139 * Normalizes a filter expression to a canonical representation while
140 * retaining logical meaning of the expression.
141 *
142 * @param filter the filter to normalize
143 * @return the normalized String version of the filter
144 */
145 public static String getNormalizedFilter( ExprNode filter )
146 {
147 BranchNormalizedVisitor visitor = new BranchNormalizedVisitor();
148
149 ExprNode result = ( ExprNode ) visitor.visit( filter );
150
151 return result.toString().trim();
152 }
153
154 static class NodeComparator implements Comparator<ExprNode>
155 {
156 @Override
157 public int compare( ExprNode o1, ExprNode o2 )
158 {
159 StringBuilder buf = new StringBuilder();
160
161 buf.setLength( 0 );
162
163 String s1;
164
165 buf.append( o1.toString() );
166
167 s1 = buf.toString();
168
169 buf.setLength( 0 );
170
171 String s2;
172
173 buf.append( o2.toString() );
174
175 s2 = buf.toString();
176
177 return s1.compareTo( s2 );
178 }
179 }
180 }