001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 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.TreeWalkerFilter;
031import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
032import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck;
033import com.puppycrawl.tools.checkstyle.api.AuditListener;
034import com.puppycrawl.tools.checkstyle.api.AutomaticBean;
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 (directly, not recursively) in the given packages.
050     * @param packages the collection of package names to use
051     * @param loader the class loader used to load Checkstyle package names
052     * @return the set of checkstyle's module classes
053     * @throws IOException if the attempt to read class path resources failed
054     * @see #isCheckstyleModule(Class)
055     */
056    public static Set<Class<?>> getCheckstyleModules(
057            Collection<String> packages, ClassLoader loader) throws IOException {
058        final ClassPath classPath = ClassPath.from(loader);
059        return packages.stream()
060                .flatMap(pkg -> classPath.getTopLevelClasses(pkg).stream())
061                .map(ClassPath.ClassInfo::load)
062                .filter(ModuleReflectionUtil::isCheckstyleModule)
063                .collect(Collectors.toSet());
064    }
065
066    /**
067     * Checks whether a class may be considered as a checkstyle module. Checkstyle's modules are
068     * non-abstract classes, which are either checkstyle's checks, file sets, filters, file filters,
069     * {@code TreeWalker} filters, audit listener, or root module.
070     * @param clazz class to check.
071     * @return true if the class may be considered as the checkstyle module.
072     */
073    public static boolean isCheckstyleModule(Class<?> clazz) {
074        return isValidCheckstyleClass(clazz)
075            && (isCheckstyleTreeWalkerCheck(clazz)
076                    || isFileSetModule(clazz)
077                    || isFilterModule(clazz)
078                    || isFileFilterModule(clazz)
079                    || isTreeWalkerFilterModule(clazz)
080                    || isAuditListener(clazz)
081                    || isRootModule(clazz));
082    }
083
084    /**
085     * Checks whether a class extends 'AutomaticBean', is non-abstract, and has a default
086     * constructor.
087     * @param clazz class to check.
088     * @return true if a class may be considered a valid production class.
089     */
090    public static boolean isValidCheckstyleClass(Class<?> clazz) {
091        return AutomaticBean.class.isAssignableFrom(clazz)
092                && !Modifier.isAbstract(clazz.getModifiers())
093                && hasDefaultConstructor(clazz)
094                && isNotXpathFileGenerator(clazz);
095    }
096
097    /**
098     * Checks if the class has a default constructor.
099     * @param clazz class to check
100     * @return true if the class has a default constructor.
101     */
102    private static boolean hasDefaultConstructor(Class<?> clazz) {
103        boolean result = false;
104        for (Constructor<?> constructor : clazz.getDeclaredConstructors()) {
105            if (constructor.getParameterCount() == 0) {
106                result = true;
107                break;
108            }
109        }
110        return result;
111    }
112
113    /**
114     * Checks whether a class may be considered as the checkstyle check
115     * which has TreeWalker as a parent.
116     * Checkstyle's checks are classes which implement 'AbstractCheck' interface.
117     * @param clazz class to check.
118     * @return true if a class may be considered as the checkstyle check.
119     */
120    public static boolean isCheckstyleTreeWalkerCheck(Class<?> clazz) {
121        return AbstractCheck.class.isAssignableFrom(clazz);
122    }
123
124    /**
125     * Checks whether a class may be considered as the checkstyle file set.
126     * Checkstyle's file sets are classes which implement 'AbstractFileSetCheck' interface.
127     * @param clazz class to check.
128     * @return true if a class may be considered as the checkstyle file set.
129     */
130    public static boolean isFileSetModule(Class<?> clazz) {
131        return AbstractFileSetCheck.class.isAssignableFrom(clazz);
132    }
133
134    /**
135     * Checks whether a class may be considered as the checkstyle filter.
136     * Checkstyle's filters are classes which implement 'Filter' interface.
137     * @param clazz class to check.
138     * @return true if a class may be considered as the checkstyle filter.
139     */
140    public static boolean isFilterModule(Class<?> clazz) {
141        return Filter.class.isAssignableFrom(clazz);
142    }
143
144    /**
145     * Checks whether a class may be considered as the checkstyle file filter.
146     * Checkstyle's file filters are classes which implement 'BeforeExecutionFileFilter' interface.
147     * @param clazz class to check.
148     * @return true if a class may be considered as the checkstyle file filter.
149     */
150    public static boolean isFileFilterModule(Class<?> clazz) {
151        return BeforeExecutionFileFilter.class.isAssignableFrom(clazz);
152    }
153
154    /**
155     * Checks whether a class may be considered as the checkstyle audit listener module.
156     * Checkstyle's audit listener modules are classes which implement 'AuditListener' interface.
157     * @param clazz class to check.
158     * @return true if a class may be considered as the checkstyle audit listener module.
159     */
160    public static boolean isAuditListener(Class<?> clazz) {
161        return AuditListener.class.isAssignableFrom(clazz);
162    }
163
164    /**
165     * Checks whether a class may be considered as the checkstyle root module.
166     * Checkstyle's root modules are classes which implement 'RootModule' interface.
167     * @param clazz class to check.
168     * @return true if a class may be considered as the checkstyle root module.
169     */
170    public static boolean isRootModule(Class<?> clazz) {
171        return RootModule.class.isAssignableFrom(clazz);
172    }
173
174    /**
175     * Checks whether a class may be considered as the checkstyle {@code TreeWalker} filter.
176     * Checkstyle's {@code TreeWalker} filters are classes which implement 'TreeWalkerFilter'
177     * interface.
178     * @param clazz class to check.
179     * @return true if a class may be considered as the checkstyle {@code TreeWalker} filter.
180     */
181    public static boolean isTreeWalkerFilterModule(Class<?> clazz) {
182        return TreeWalkerFilter.class.isAssignableFrom(clazz);
183    }
184
185    /**
186     * Checks whether a class is {@code XpathFileGeneratorAstFilter} or
187     * {@code XpathFileGeneratorAuditListener}.
188     * See issue #102 https://github.com/checkstyle/checkstyle/issues/102
189     * @param clazz class to check.
190     * @return true if a class name starts with `XpathFileGenerator`.
191     */
192    private static boolean isNotXpathFileGenerator(Class<?> clazz) {
193        return !clazz.getSimpleName().startsWith("XpathFileGenerator");
194    }
195}