Source code

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.checks;
021
022import java.util.Optional;
023import java.util.regex.Pattern;
024
025import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
026import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
027import com.puppycrawl.tools.checkstyle.api.DetailAST;
028import com.puppycrawl.tools.checkstyle.api.FullIdent;
029import com.puppycrawl.tools.checkstyle.api.TokenTypes;
030
031/**
032 * <p>
033 * Detects uncommented {@code main} methods.
034 * </p>
035 * <p>
036 * Rationale: A {@code main} method is often used for debugging purposes.
037 * When debugging is finished, developers often forget to remove the method,
038 * which changes the API and increases the size of the resulting class or JAR file.
039 * With the exception of the real program entry points, all {@code main} methods
040 * should be removed or commented out of the sources.
041 * </p>
042 * <ul>
043 * <li>
044 * Property {@code excludedClasses} - Specify pattern for qualified names of
045 * classes which are allowed to have a {@code main} method.
046 * Type is {@code java.util.regex.Pattern}.
047 * Default value is {@code "^$" (empty)}.
048 * </li>
049 * </ul>
050 * <p>
051 * To configure the check:
052 * </p>
053 * <pre>
054 * &lt;module name=&quot;UncommentedMain&quot;/&gt;
055 * </pre>
056 * <p>Example:</p>
057 * <pre>
058 * public class Game {
059 *    public static void main(String... args){}   // violation
060 * }
061 *
062 * public class Main {
063 *    public static void main(String[] args){}   // violation
064 * }
065 *
066 * public class Launch {
067 *    //public static void main(String[] args){} // OK
068 * }
069 *
070 * public class Start {
071 *    public void main(){}                       // OK
072 * }
073 * </pre>
074 * <p>
075 * To configure the check to allow the {@code main} method for all classes with "Main" name:
076 * </p>
077 * <pre>
078 * &lt;module name=&quot;UncommentedMain&quot;&gt;
079 *   &lt;property name=&quot;excludedClasses&quot; value=&quot;\.Main$&quot;/&gt;
080 * &lt;/module&gt;
081 * </pre>
082 * <p>Example:</p>
083 * <pre>
084 * public class Game {
085 *    public static void main(String... args){}   // violation
086 * }
087 *
088 * public class Main {
089 *    public static void main(String[] args){}   // OK
090 * }
091 *
092 * public class Launch {
093 *    //public static void main(String[] args){} // OK
094 * }
095 *
096 * public class Start {
097 *    public void main(){}                       // OK
098 * }
099 * </pre>
100 * <p>
101 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
102 * </p>
103 * <p>
104 * Violation Message Keys:
105 * </p>
106 * <ul>
107 * <li>
108 * {@code uncommented.main}
109 * </li>
110 * </ul>
111 *
112 * @since 3.2
113 */
114@FileStatefulCheck
115public class UncommentedMainCheck
116    extends AbstractCheck {
117
118    /**
119     * A key is pointing to the warning message text in "messages.properties"
120     * file.
121     */
122    public static final String MSG_KEY = "uncommented.main";
123
124    /**
125     * Specify pattern for qualified names of classes which are allowed to
126     * have a {@code main} method.
127     */
128    private Pattern excludedClasses = Pattern.compile("^$");
129    /** Current class name. */
130    private String currentClass;
131    /** Current package. */
132    private FullIdent packageName;
133    /** Class definition depth. */
134    private int classDepth;
135
136    /**
137     * Setter to specify pattern for qualified names of classes which are allowed
138     * to have a {@code main} method.
139     *
140     * @param excludedClasses a pattern
141     */
142    public void setExcludedClasses(Pattern excludedClasses) {
143        this.excludedClasses = excludedClasses;
144    }
145
146    @Override
147    public int[] getAcceptableTokens() {
148        return getRequiredTokens();
149    }
150
151    @Override
152    public int[] getDefaultTokens() {
153        return getRequiredTokens();
154    }
155
156    @Override
157    public int[] getRequiredTokens() {
158        return new int[] {
159            TokenTypes.METHOD_DEF,
160            TokenTypes.CLASS_DEF,
161            TokenTypes.PACKAGE_DEF,
162        };
163    }
164
165    @Override
166    public void beginTree(DetailAST rootAST) {
167        packageName = FullIdent.createFullIdent(null);
168        currentClass = null;
169        classDepth = 0;
170    }
171
172    @Override
173    public void leaveToken(DetailAST ast) {
174        if (ast.getType() == TokenTypes.CLASS_DEF) {
175            classDepth--;
176        }
177    }
178
179    @Override
180    public void visitToken(DetailAST ast) {
181        switch (ast.getType()) {
182            case TokenTypes.PACKAGE_DEF:
183                visitPackageDef(ast);
184                break;
185            case TokenTypes.CLASS_DEF:
186                visitClassDef(ast);
187                break;
188            case TokenTypes.METHOD_DEF:
189                visitMethodDef(ast);
190                break;
191            default:
192                throw new IllegalStateException(ast.toString());
193        }
194    }
195
196    /**
197     * Sets current package.
198     *
199     * @param packageDef node for package definition
200     */
201    private void visitPackageDef(DetailAST packageDef) {
202        packageName = FullIdent.createFullIdent(packageDef.getLastChild()
203                .getPreviousSibling());
204    }
205
206    /**
207     * If not inner class then change current class name.
208     *
209     * @param classDef node for class definition
210     */
211    private void visitClassDef(DetailAST classDef) {
212        // we are not use inner classes because they can not
213        // have static methods
214        if (classDepth == 0) {
215            final DetailAST ident = classDef.findFirstToken(TokenTypes.IDENT);
216            currentClass = packageName.getText() + "." + ident.getText();
217            classDepth++;
218        }
219    }
220
221    /**
222     * Checks method definition if this is
223     * {@code public static void main(String[])}.
224     *
225     * @param method method definition node
226     */
227    private void visitMethodDef(DetailAST method) {
228        if (classDepth == 1
229                // method not in inner class or in interface definition
230                && checkClassName()
231                && checkName(method)
232                && checkModifiers(method)
233                && checkType(method)
234                && checkParams(method)) {
235            log(method, MSG_KEY);
236        }
237    }
238
239    /**
240     * Checks that current class is not excluded.
241     *
242     * @return true if check passed, false otherwise
243     */
244    private boolean checkClassName() {
245        return !excludedClasses.matcher(currentClass).find();
246    }
247
248    /**
249     * Checks that method name is @quot;main@quot;.
250     *
251     * @param method the METHOD_DEF node
252     * @return true if check passed, false otherwise
253     */
254    private static boolean checkName(DetailAST method) {
255        final DetailAST ident = method.findFirstToken(TokenTypes.IDENT);
256        return "main".equals(ident.getText());
257    }
258
259    /**
260     * Checks that method has final and static modifiers.
261     *
262     * @param method the METHOD_DEF node
263     * @return true if check passed, false otherwise
264     */
265    private static boolean checkModifiers(DetailAST method) {
266        final DetailAST modifiers =
267            method.findFirstToken(TokenTypes.MODIFIERS);
268
269        return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null
270            && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) != null;
271    }
272
273    /**
274     * Checks that return type is {@code void}.
275     *
276     * @param method the METHOD_DEF node
277     * @return true if check passed, false otherwise
278     */
279    private static boolean checkType(DetailAST method) {
280        final DetailAST type =
281            method.findFirstToken(TokenTypes.TYPE).getFirstChild();
282        return type.getType() == TokenTypes.LITERAL_VOID;
283    }
284
285    /**
286     * Checks that method has only {@code String[]} or only {@code String...} param.
287     *
288     * @param method the METHOD_DEF node
289     * @return true if check passed, false otherwise
290     */
291    private static boolean checkParams(DetailAST method) {
292        boolean checkPassed = false;
293        final DetailAST params = method.findFirstToken(TokenTypes.PARAMETERS);
294
295        if (params.getChildCount() == 1) {
296            final DetailAST parameterType = params.getFirstChild().findFirstToken(TokenTypes.TYPE);
297            final Optional<DetailAST> arrayDecl = Optional.ofNullable(
298                parameterType.findFirstToken(TokenTypes.ARRAY_DECLARATOR));
299            final Optional<DetailAST> varargs = Optional.ofNullable(
300                params.getFirstChild().findFirstToken(TokenTypes.ELLIPSIS));
301
302            if (arrayDecl.isPresent()) {
303                checkPassed = isStringType(arrayDecl.get().getFirstChild());
304            }
305            else if (varargs.isPresent()) {
306                checkPassed = isStringType(parameterType.getFirstChild());
307            }
308        }
309        return checkPassed;
310    }
311
312    /**
313     * Whether the type is java.lang.String.
314     *
315     * @param typeAst the type to check.
316     * @return true, if the type is java.lang.String.
317     */
318    private static boolean isStringType(DetailAST typeAst) {
319        final FullIdent type = FullIdent.createFullIdent(typeAst);
320        return "String".equals(type.getText())
321            || "java.lang.String".equals(type.getText());
322    }
323
324}