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 *
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 * Setter to specify Xpath query.
80 *
81 * @param query Xpath query.
82 * @throws IllegalStateException if creation of xpath expression fails
83 * @since 8.39
84 */
85 public void setQuery(String query) {
86 this.query = query;
87 if (!query.isEmpty()) {
88 try {
89 final XPathEvaluator xpathEvaluator =
90 new XPathEvaluator(Configuration.newConfiguration());
91 xpathExpression = xpathEvaluator.createExpression(query);
92 }
93 catch (XPathException exc) {
94 throw new IllegalStateException("Creating Xpath expression failed: " + query, exc);
95 }
96 }
97 }
98
99 @Override
100 public int[] getDefaultTokens() {
101 return getRequiredTokens();
102 }
103
104 @Override
105 public int[] getAcceptableTokens() {
106 return getRequiredTokens();
107 }
108
109 @Override
110 public int[] getRequiredTokens() {
111 return CommonUtil.EMPTY_INT_ARRAY;
112 }
113
114 @Override
115 public boolean isCommentNodesRequired() {
116 return true;
117 }
118
119 @Override
120 public void beginTree(DetailAST rootAST) {
121 if (!query.isEmpty()) {
122 final List<DetailAST> matchingNodes = findMatchingNodesByXpathQuery(rootAST);
123 matchingNodes.forEach(node -> log(node, MSG_KEY));
124 }
125 }
126
127 /**
128 * Find nodes that match query.
129 *
130 * @param rootAST root node
131 * @return list of matching nodes
132 * @throws IllegalStateException if evaluation of xpath query fails
133 */
134 private List<DetailAST> findMatchingNodesByXpathQuery(DetailAST rootAST) {
135 try {
136 final RootNode rootNode = new RootNode(rootAST);
137 final XPathDynamicContext xpathDynamicContext =
138 xpathExpression.createDynamicContext(rootNode);
139 final List<Item> matchingItems = xpathExpression.evaluate(xpathDynamicContext);
140 return matchingItems.stream()
141 .map(item -> (DetailAST) ((AbstractNode) item).getUnderlyingNode())
142 .toList();
143 }
144 catch (XPathException exc) {
145 throw new IllegalStateException("Evaluation of Xpath query failed: " + query, exc);
146 }
147 }
148 }