Source code

001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
018///////////////////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.utils;
021
022import java.io.IOException;
023import java.lang.reflect.Constructor;
024import java.lang.reflect.Modifier;
025import java.util.Collection;
026import java.util.Set;
027import java.util.stream.Collectors;
028
029import com.google.common.reflect.ClassPath;
030import com.puppycrawl.tools.checkstyle.AbstractAutomaticBean;
031import com.puppycrawl.tools.checkstyle.TreeWalkerFilter;
032import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
033import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck;
034import com.puppycrawl.tools.checkstyle.api.AuditListener;
035import com.puppycrawl.tools.checkstyle.api.BeforeExecutionFileFilter;
036import com.puppycrawl.tools.checkstyle.api.Filter;
037import com.puppycrawl.tools.checkstyle.api.RootModule;
038
039/**
040 * Contains utility methods for module reflection.
041 */
042public final class ModuleReflectionUtil {
043
044 /** Prevent instantiation. */
045 private ModuleReflectionUtil() {
046 }
047
048 /**
049 * Gets checkstyle's modules classes (directly, not recursively) in the given packages.
050 *
051 * @param packages the collection of package names to use
052 * @param loader the class loader used to load Checkstyle package names
053 * @return the set of checkstyle's module classes
054 * @throws IOException if the attempt to read class path resources failed
055 * @see #isCheckstyleModule(Class)
056 */
057 public static Set<Class<?>> getCheckstyleModules(
058 Collection<String> packages, ClassLoader loader) throws IOException {
059 final ClassPath classPath = ClassPath.from(loader);
060 return packages.stream()
061 .flatMap(pkg -> classPath.getTopLevelClasses(pkg).stream())
062 .map(ClassPath.ClassInfo::load)
063 .filter(ModuleReflectionUtil::isCheckstyleModule)
064 .collect(Collectors.toUnmodifiableSet());
065 }
066
067 /**
068 * Checks whether a class may be considered as a checkstyle module.
069 * Checkstyle's modules are classes which extend 'AutomaticBean', is
070 * non-abstract, and has a default constructor.
071 *
072 * @param clazz class to check.
073 * @return true if a class may be considered a valid production class.
074 */
075 public static boolean isCheckstyleModule(Class<?> clazz) {
076 return AbstractAutomaticBean.class.isAssignableFrom(clazz)
077 && !Modifier.isAbstract(clazz.getModifiers())
078 && hasDefaultConstructor(clazz)
079 && isNotXpathFileGenerator(clazz);
080 }
081
082 /**
083 * Checks if the class has a default constructor.
084 *
085 * @param clazz class to check
086 * @return true if the class has a default constructor.
087 */
088 private static boolean hasDefaultConstructor(Class<?> clazz) {
089 boolean result = false;
090 for (Constructor<?> constructor : clazz.getDeclaredConstructors()) {
091 if (constructor.getParameterCount() == 0) {
092 result = true;
093 break;
094 }
095 }
096 return result;
097 }
098
099 /**
100 * Checks whether a class may be considered as the checkstyle check
101 * which has TreeWalker as a parent.
102 * Checkstyle's checks are classes which implement 'AbstractCheck' interface.
103 *
104 * @param clazz class to check.
105 * @return true if a class may be considered as the checkstyle check.
106 */
107 public static boolean isCheckstyleTreeWalkerCheck(Class<?> clazz) {
108 return AbstractCheck.class.isAssignableFrom(clazz);
109 }
110
111 /**
112 * Checks whether a class may be considered as the checkstyle file set.
113 * Checkstyle's file sets are classes which implement 'AbstractFileSetCheck' interface.
114 *
115 * @param clazz class to check.
116 * @return true if a class may be considered as the checkstyle file set.
117 */
118 public static boolean isFileSetModule(Class<?> clazz) {
119 return AbstractFileSetCheck.class.isAssignableFrom(clazz);
120 }
121
122 /**
123 * Checks whether a class may be considered as the checkstyle filter.
124 * Checkstyle's filters are classes which implement 'Filter' interface.
125 *
126 * @param clazz class to check.
127 * @return true if a class may be considered as the checkstyle filter.
128 */
129 public static boolean isFilterModule(Class<?> clazz) {
130 return Filter.class.isAssignableFrom(clazz);
131 }
132
133 /**
134 * Checks whether a class may be considered as the checkstyle file filter.
135 * Checkstyle's file filters are classes which implement 'BeforeExecutionFileFilter' interface.
136 *
137 * @param clazz class to check.
138 * @return true if a class may be considered as the checkstyle file filter.
139 */
140 public static boolean isFileFilterModule(Class<?> clazz) {
141 return BeforeExecutionFileFilter.class.isAssignableFrom(clazz);
142 }
143
144 /**
145 * Checks whether a class may be considered as the checkstyle audit listener module.
146 * Checkstyle's audit listener modules are classes which implement 'AuditListener' interface.
147 *
148 * @param clazz class to check.
149 * @return true if a class may be considered as the checkstyle audit listener module.
150 */
151 public static boolean isAuditListener(Class<?> clazz) {
152 return AuditListener.class.isAssignableFrom(clazz);
153 }
154
155 /**
156 * Checks whether a class may be considered as the checkstyle root module.
157 * Checkstyle's root modules are classes which implement 'RootModule' interface.
158 *
159 * @param clazz class to check.
160 * @return true if a class may be considered as the checkstyle root module.
161 */
162 public static boolean isRootModule(Class<?> clazz) {
163 return RootModule.class.isAssignableFrom(clazz);
164 }
165
166 /**
167 * Checks whether a class may be considered as the checkstyle {@code TreeWalker} filter.
168 * Checkstyle's {@code TreeWalker} filters are classes which implement 'TreeWalkerFilter'
169 * interface.
170 *
171 * @param clazz class to check.
172 * @return true if a class may be considered as the checkstyle {@code TreeWalker} filter.
173 */
174 public static boolean isTreeWalkerFilterModule(Class<?> clazz) {
175 return TreeWalkerFilter.class.isAssignableFrom(clazz);
176 }
177
178 /**
179 * Checks whether a class is {@code XpathFileGeneratorAstFilter} or
180 * {@code XpathFileGeneratorAuditListener}.
181 * See issue <a href="https://github.com/checkstyle/checkstyle/issues/102">#102</a>
182 *
183 * @param clazz class to check.
184 * @return true if a class name starts with `XpathFileGenerator`.
185 */
186 private static boolean isNotXpathFileGenerator(Class<?> clazz) {
187 return !clazz.getSimpleName().startsWith("XpathFileGenerator");
188 }
189}