1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2026 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
24 import com.puppycrawl.tools.checkstyle.StatelessCheck;
25 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
26 import com.puppycrawl.tools.checkstyle.api.DetailAST;
27 import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
28 import com.puppycrawl.tools.checkstyle.xpath.AbstractNode;
29 import com.puppycrawl.tools.checkstyle.xpath.RootNode;
30 import net.sf.saxon.Configuration;
31 import net.sf.saxon.om.Item;
32 import net.sf.saxon.sxpath.XPathDynamicContext;
33 import net.sf.saxon.sxpath.XPathEvaluator;
34 import net.sf.saxon.sxpath.XPathExpression;
35 import net.sf.saxon.trans.XPathException;
36
37 /**
38 * <div>
39 * Evaluates Xpath query and report violation on all matching AST nodes. This check allows
40 * user to implement custom checks using Xpath. If Xpath query is not specified explicitly,
41 * then the check does nothing.
42 * </div>
43 *
44 * <p>
45 * It is recommended to define custom message for violation to explain what is not allowed and what
46 * to use instead, default message might be too abstract. To customize a message you need to
47 * add {@code message} element with <b>matchxpath.match</b> as {@code key} attribute and
48 * desired message as {@code value} attribute.
49 * </p>
50 *
51 * <p>
52 * Please read more about Xpath syntax at
53 * <a href="https://www.saxonica.com/html/documentation10/expressions/index.html">Xpath Syntax</a>.
54 * Information regarding Xpath functions can be found at
55 * <a href="https://www.saxonica.com/html/documentation10/functions/fn/index.html">
56 * XSLT/XPath Reference</a>.
57 * Note, that <b>@text</b> attribute can be used only with token types that are listed in
58 * <a href="https://github.com/checkstyle/checkstyle/search?q=%22TOKEN_TYPES_WITH_TEXT_ATTRIBUTE+%3D+Arrays.asList%22">
59 * XpathUtil</a>.
60 * </p>
61 *
62 * @since 8.39
63 */
64 @StatelessCheck
65 public class MatchXpathCheck extends AbstractCheck {
66
67 /**
68 * A key is pointing to the warning message text provided by user.
69 */
70 public static final String MSG_KEY = "matchxpath.match";
71
72 /** Specify Xpath query. */
73 private String query = "";
74
75 /** Xpath expression. */
76 private XPathExpression xpathExpression;
77
78 /**
79 * Creates a new {@code MatchXpathCheck} instance.
80 */
81 public MatchXpathCheck() {
82 // no code by default
83 }
84
85 /**
86 * Setter to specify Xpath query.
87 *
88 * @param query Xpath query.
89 * @throws IllegalStateException if creation of xpath expression fails
90 * @since 8.39
91 */
92 public void setQuery(String query) {
93 this.query = query;
94 if (!query.isEmpty()) {
95 try {
96 final XPathEvaluator xpathEvaluator =
97 new XPathEvaluator(Configuration.newConfiguration());
98 xpathExpression = xpathEvaluator.createExpression(query);
99 }
100 catch (XPathException exc) {
101 throw new IllegalStateException("Creating Xpath expression failed: " + query, exc);
102 }
103 }
104 }
105
106 @Override
107 public int[] getDefaultTokens() {
108 return getRequiredTokens();
109 }
110
111 @Override
112 public int[] getAcceptableTokens() {
113 return getRequiredTokens();
114 }
115
116 @Override
117 public int[] getRequiredTokens() {
118 return CommonUtil.EMPTY_INT_ARRAY;
119 }
120
121 @Override
122 public boolean isCommentNodesRequired() {
123 return true;
124 }
125
126 @Override
127 public void beginTree(DetailAST rootAST) {
128 if (!query.isEmpty()) {
129 final List<DetailAST> matchingNodes = findMatchingNodesByXpathQuery(rootAST);
130 matchingNodes.forEach(node -> log(node, MSG_KEY));
131 }
132 }
133
134 /**
135 * Find nodes that match query.
136 *
137 * @param rootAST root node
138 * @return list of matching nodes
139 * @throws IllegalStateException if evaluation of xpath query fails
140 */
141 private List<DetailAST> findMatchingNodesByXpathQuery(DetailAST rootAST) {
142 try {
143 final RootNode rootNode = new RootNode(rootAST);
144 final XPathDynamicContext xpathDynamicContext =
145 xpathExpression.createDynamicContext(rootNode);
146 final List<Item> matchingItems = xpathExpression.evaluate(xpathDynamicContext);
147 return matchingItems.stream()
148 .map(item -> (DetailAST) ((AbstractNode) item).getUnderlyingNode())
149 .toList();
150 }
151 catch (XPathException exc) {
152 throw new IllegalStateException("Evaluation of Xpath query failed: " + query, exc);
153 }
154 }
155
156 }