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 * https://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 @Override
48 public Object visit( ExprNode node )
49 {
50 if ( !( node instanceof BranchNode ) )
51 {
52 return null;
53 }
54
55 BranchNode branch = ( BranchNode ) node;
56
57 Comparator<ExprNode> nodeComparator = new NodeComparator();
58
59 Set<ExprNode> set = new TreeSet<>( nodeComparator );
60
61 List<ExprNode> children = branch.getChildren();
62
63 for ( ExprNode child : branch.getChildren() )
64 {
65 if ( !child.isLeaf() )
66 {
67 ExprNode newChild = ( ExprNode ) visit( child );
68
69 if ( newChild != null )
70 {
71 set.add( newChild );
72 }
73 }
74 else
75 {
76 set.add( child );
77 }
78 }
79
80 children.clear();
81
82 children.addAll( set );
83
84 return branch;
85 }
86
87
88 /**
89 * {@inheritDoc}
90 */
91 @Override
92 public boolean canVisit( ExprNode node )
93 {
94 return node instanceof BranchNode;
95 }
96
97
98 /**
99 * {@inheritDoc}
100 */
101 @Override
102 public boolean isPrefix()
103 {
104 return false;
105 }
106
107
108 /**
109 * {@inheritDoc}
110 */
111 @Override
112 public List<ExprNode> getOrder( BranchNode node, List<ExprNode> children )
113 {
114 return children;
115 }
116
117
118 /**
119 * Normalizes a filter expression to a canonical representation while
120 * retaining logical meaning of the expression.
121 *
122 * @param schemaManager The SchemaManager
123 * @param filter the filter to normalize
124 * @return the normalized version of the filter
125 * @throws java.text.ParseException if the filter is malformed
126 */
127 public static String getNormalizedFilter( SchemaManager schemaManager, String filter ) throws ParseException
128 {
129 ExprNode originalNode = FilterParser.parse( schemaManager, filter );
130
131 return getNormalizedFilter( originalNode );
132 }
133
134
135 /**
136 * Normalizes a filter expression to a canonical representation while
137 * retaining logical meaning of the expression.
138 *
139 * @param filter
140 * the filter to normalize
141 * @return the normalized String version of the filter
142 */
143 public static String getNormalizedFilter( ExprNode filter )
144 {
145 BranchNormalizedVisitor visitor = new BranchNormalizedVisitor();
146
147 ExprNode result = ( ExprNode ) visitor.visit( filter );
148
149 return result.toString().trim();
150 }
151
152
153 static class NodeComparator implements Comparator<ExprNode>
154 {
155 @Override
156 public int compare( ExprNode o1, ExprNode o2 )
157 {
158 String s1 = o1.toString();
159 String s2 = o2.toString();
160
161 return s1.compareTo( s2 );
162 }
163 }
164 }