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
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 * <ul>
62 * <li>
63 * Property {@code query} - Specify Xpath query.
64 * Type is {@code java.lang.String}.
65 * Default value is {@code ""}.
66 * </li>
67 * </ul>
68 *
69 * <p>
70 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
71 * </p>
72 *
73 * <p>
74 * Violation Message Keys:
75 * </p>
76 * <ul>
77 * <li>
78 * {@code matchxpath.match}
79 * </li>
80 * </ul>
81 *
82 * @since 8.39
83 */
84 @StatelessCheck
85 public class MatchXpathCheck extends AbstractCheck {
86
87 /**
88 * A key is pointing to the warning message text provided by user.
89 */
90 public static final String MSG_KEY = "matchxpath.match";
91
92 /** Specify Xpath query. */
93 private String query = "";
94
95 /** Xpath expression. */
96 private XPathExpression xpathExpression;
97
98 /**
99 * Setter to specify Xpath query.
100 *
101 * @param query Xpath query.
102 * @throws IllegalStateException if creation of xpath expression fails
103 * @since 8.39
104 */
105 public void setQuery(String query) {
106 this.query = query;
107 if (!query.isEmpty()) {
108 try {
109 final XPathEvaluator xpathEvaluator =
110 new XPathEvaluator(Configuration.newConfiguration());
111 xpathExpression = xpathEvaluator.createExpression(query);
112 }
113 catch (XPathException exc) {
114 throw new IllegalStateException("Creating Xpath expression failed: " + query, exc);
115 }
116 }
117 }
118
119 @Override
120 public int[] getDefaultTokens() {
121 return getRequiredTokens();
122 }
123
124 @Override
125 public int[] getAcceptableTokens() {
126 return getRequiredTokens();
127 }
128
129 @Override
130 public int[] getRequiredTokens() {
131 return CommonUtil.EMPTY_INT_ARRAY;
132 }
133
134 @Override
135 public boolean isCommentNodesRequired() {
136 return true;
137 }
138
139 @Override
140 public void beginTree(DetailAST rootAST) {
141 if (!query.isEmpty()) {
142 final List<DetailAST> matchingNodes = findMatchingNodesByXpathQuery(rootAST);
143 matchingNodes.forEach(node -> log(node, MSG_KEY));
144 }
145 }
146
147 /**
148 * Find nodes that match query.
149 *
150 * @param rootAST root node
151 * @return list of matching nodes
152 * @throws IllegalStateException if evaluation of xpath query fails
153 */
154 private List<DetailAST> findMatchingNodesByXpathQuery(DetailAST rootAST) {
155 try {
156 final RootNode rootNode = new RootNode(rootAST);
157 final XPathDynamicContext xpathDynamicContext =
158 xpathExpression.createDynamicContext(rootNode);
159 final List<Item> matchingItems = xpathExpression.evaluate(xpathDynamicContext);
160 return matchingItems.stream()
161 .map(item -> (DetailAST) ((AbstractNode) item).getUnderlyingNode())
162 .toList();
163 }
164 catch (XPathException exc) {
165 throw new IllegalStateException("Evaluation of Xpath query failed: " + query, exc);
166 }
167 }
168 }