1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2025 the original author or authors.
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ///////////////////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle.checks.coding;
21
22 import java.util.List;
23 import java.util.stream.Collectors;
24
25 import com.puppycrawl.tools.checkstyle.StatelessCheck;
26 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
27 import com.puppycrawl.tools.checkstyle.api.DetailAST;
28 import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
29 import com.puppycrawl.tools.checkstyle.xpath.AbstractNode;
30 import com.puppycrawl.tools.checkstyle.xpath.RootNode;
31 import net.sf.saxon.Configuration;
32 import net.sf.saxon.om.Item;
33 import net.sf.saxon.sxpath.XPathDynamicContext;
34 import net.sf.saxon.sxpath.XPathEvaluator;
35 import net.sf.saxon.sxpath.XPathExpression;
36 import net.sf.saxon.trans.XPathException;
37
38 /**
39 * <div>
40 * Evaluates Xpath query and report violation on all matching AST nodes. This check allows
41 * user to implement custom checks using Xpath. If Xpath query is not specified explicitly,
42 * then the check does nothing.
43 * </div>
44 *
45 * <p>
46 * It is recommended to define custom message for violation to explain what is not allowed and what
47 * to use instead, default message might be too abstract. To customize a message you need to
48 * add {@code message} element with <b>matchxpath.match</b> as {@code key} attribute and
49 * desired message as {@code value} attribute.
50 * </p>
51 *
52 * <p>
53 * Please read more about Xpath syntax at
54 * <a href="https://www.saxonica.com/html/documentation10/expressions/index.html">Xpath Syntax</a>.
55 * Information regarding Xpath functions can be found at
56 * <a href="https://www.saxonica.com/html/documentation10/functions/fn/index.html">
57 * XSLT/XPath Reference</a>.
58 * Note, that <b>@text</b> attribute can be used only with token types that are listed in
59 * <a href="https://github.com/checkstyle/checkstyle/search?q=%22TOKEN_TYPES_WITH_TEXT_ATTRIBUTE+%3D+Arrays.asList%22">
60 * XpathUtil</a>.
61 * </p>
62 * <ul>
63 * <li>
64 * Property {@code query} - Specify Xpath query.
65 * Type is {@code java.lang.String}.
66 * Default value is {@code ""}.
67 * </li>
68 * </ul>
69 *
70 * <p>
71 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
72 * </p>
73 *
74 * <p>
75 * Violation Message Keys:
76 * </p>
77 * <ul>
78 * <li>
79 * {@code matchxpath.match}
80 * </li>
81 * </ul>
82 *
83 * @since 8.39
84 */
85 @StatelessCheck
86 public class MatchXpathCheck extends AbstractCheck {
87
88 /**
89 * A key is pointing to the warning message text provided by user.
90 */
91 public static final String MSG_KEY = "matchxpath.match";
92
93 /** Specify Xpath query. */
94 private String query = "";
95
96 /** Xpath expression. */
97 private XPathExpression xpathExpression;
98
99 /**
100 * Setter to specify Xpath query.
101 *
102 * @param query Xpath query.
103 * @throws IllegalStateException if creation of xpath expression fails
104 * @since 8.39
105 */
106 public void setQuery(String query) {
107 this.query = query;
108 if (!query.isEmpty()) {
109 try {
110 final XPathEvaluator xpathEvaluator =
111 new XPathEvaluator(Configuration.newConfiguration());
112 xpathExpression = xpathEvaluator.createExpression(query);
113 }
114 catch (XPathException ex) {
115 throw new IllegalStateException("Creating Xpath expression failed: " + query, ex);
116 }
117 }
118 }
119
120 @Override
121 public int[] getDefaultTokens() {
122 return getRequiredTokens();
123 }
124
125 @Override
126 public int[] getAcceptableTokens() {
127 return getRequiredTokens();
128 }
129
130 @Override
131 public int[] getRequiredTokens() {
132 return CommonUtil.EMPTY_INT_ARRAY;
133 }
134
135 @Override
136 public boolean isCommentNodesRequired() {
137 return true;
138 }
139
140 @Override
141 public void beginTree(DetailAST rootAST) {
142 if (!query.isEmpty()) {
143 final List<DetailAST> matchingNodes = findMatchingNodesByXpathQuery(rootAST);
144 matchingNodes.forEach(node -> log(node, MSG_KEY));
145 }
146 }
147
148 /**
149 * Find nodes that match query.
150 *
151 * @param rootAST root node
152 * @return list of matching nodes
153 * @throws IllegalStateException if evaluation of xpath query fails
154 */
155 private List<DetailAST> findMatchingNodesByXpathQuery(DetailAST rootAST) {
156 try {
157 final RootNode rootNode = new RootNode(rootAST);
158 final XPathDynamicContext xpathDynamicContext =
159 xpathExpression.createDynamicContext(rootNode);
160 final List<Item> matchingItems = xpathExpression.evaluate(xpathDynamicContext);
161 return matchingItems.stream()
162 .map(item -> (DetailAST) ((AbstractNode) item).getUnderlyingNode())
163 .collect(Collectors.toUnmodifiableList());
164 }
165 catch (XPathException ex) {
166 throw new IllegalStateException("Evaluation of Xpath query failed: " + query, ex);
167 }
168 }
169 }