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1   ///////////////////////////////////////////////////////////////////////////////////////////////
2   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3   // Copyright (C) 2001-2026 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.imports;
21  
22  import java.util.HashSet;
23  import java.util.Set;
24  
25  import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
26  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
27  import com.puppycrawl.tools.checkstyle.api.DetailAST;
28  import com.puppycrawl.tools.checkstyle.api.FullIdent;
29  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
30  
31  /**
32   * <div>
33   * Checks that there are no import statements that use the {@code *} notation.
34   * </div>
35   *
36   * <p>
37   * Rationale: Importing all classes from a package or static
38   * members from a class leads to tight coupling between packages
39   * or classes and might lead to problems when a new version of a
40   * library introduces name clashes.
41   * </p>
42   *
43   * <p>
44   * Notes:
45   * Note that property {@code excludes} is not recursive, subpackages of excluded
46   * packages are not automatically excluded.
47   * </p>
48   *
49   * @since 3.0
50   */
51  @FileStatefulCheck
52  public class AvoidStarImportCheck
53      extends AbstractCheck {
54  
55      /**
56       * A key is pointing to the warning message text in "messages.properties"
57       * file.
58       */
59      public static final String MSG_KEY = "import.avoidStar";
60  
61      /**
62       * A key is pointing to the warning message text in "messages.properties"
63       * file.
64       */
65      public static final String MSG_COUNT = "import.avoidStarCount";
66  
67      /** Suffix for the star import. */
68      private static final String STAR_IMPORT_SUFFIX = ".*";
69  
70      /**
71       * Specify packages where starred class imports are
72       * allowed and classes where starred static member imports are allowed.
73       */
74      private final Set<String> excludes = new HashSet<>();
75  
76      /**
77       * Control whether to allow starred class imports like
78       * {@code import java.util.*;}.
79       */
80      private boolean allowClassImports;
81  
82      /**
83       * Control whether to allow starred static member imports like
84       * {@code import static org.junit.Assert.*;}.
85       */
86      private boolean allowStaticMemberImports;
87  
88      /**
89       * Maximum number of allowed star imports.
90       */
91      private int maxAllowedStarImports;
92  
93      /**
94       * Counter for used star imports.
95       */
96      private int currentStarImportsCount;
97  
98      @Override
99      public int[] getDefaultTokens() {
100         return getRequiredTokens();
101     }
102 
103     @Override
104     public int[] getAcceptableTokens() {
105         return getRequiredTokens();
106     }
107 
108     @Override
109     public int[] getRequiredTokens() {
110         // original implementation checks both IMPORT and STATIC_IMPORT tokens to avoid ".*" imports
111         // however user can allow using "import" or "import static"
112         // by configuring allowClassImports and allowStaticMemberImports
113         // To avoid potential confusion when user specifies conflicting options on configuration
114         // (see example below) we are adding both tokens to Required list
115         //   <module name="AvoidStarImport">
116         //      <property name="tokens" value="IMPORT"/>
117         //      <property name="allowStaticMemberImports" value="false"/>
118         //   </module>
119         return new int[] {TokenTypes.IMPORT, TokenTypes.STATIC_IMPORT};
120     }
121 
122     /**
123      * Setter to specify packages where starred class imports are
124      * allowed and classes where starred static member imports are allowed.
125      *
126      * @param excludesParam package names/fully-qualifies class names
127      *     where star imports are ok
128      * @since 3.2
129      */
130     public void setExcludes(String... excludesParam) {
131         for (final String exclude : excludesParam) {
132             if (exclude.endsWith(STAR_IMPORT_SUFFIX)) {
133                 excludes.add(exclude);
134             }
135             else {
136                 excludes.add(exclude + STAR_IMPORT_SUFFIX);
137             }
138         }
139     }
140 
141     /**
142      * Setter to control whether to allow starred class imports like
143      * {@code import java.util.*;}.
144      *
145      * @param allow true to allow false to disallow
146      * @since 5.3
147      */
148     public void setAllowClassImports(boolean allow) {
149         allowClassImports = allow;
150     }
151 
152     /**
153      * Setter to control whether to allow starred static member imports like
154      * {@code import static org.junit.Assert.*;}.
155      *
156      * @param allow true to allow false to disallow
157      * @since 5.3
158      */
159     public void setAllowStaticMemberImports(boolean allow) {
160         allowStaticMemberImports = allow;
161     }
162 
163     /**
164      * Setter to control how many star imports are allowed.
165      *
166      * @param count the number of star imports allowed
167      * @since 13.5.0
168      */
169     public void setMaxAllowedStarImports(int count) {
170         maxAllowedStarImports = count;
171     }
172 
173     @Override
174     public void beginTree(DetailAST rootAST) {
175         currentStarImportsCount = 0;
176     }
177 
178     @Override
179     public void visitToken(final DetailAST ast) {
180         if (ast.getType() == TokenTypes.IMPORT) {
181             if (!allowClassImports) {
182                 final DetailAST startingDot = ast.getFirstChild();
183                 logsStarredImportViolation(startingDot);
184             }
185         }
186         else if (!allowStaticMemberImports) {
187             // must navigate past the static keyword
188             final DetailAST startingDot = ast.getFirstChild().getNextSibling();
189             logsStarredImportViolation(startingDot);
190         }
191     }
192 
193     /**
194      * Gets the full import identifier.  If the import is a starred import and
195      * it's not excluded then a violation is logged.
196      *
197      * @param startingDot the starting dot for the import statement
198      */
199     private void logsStarredImportViolation(DetailAST startingDot) {
200         final FullIdent name = FullIdent.createFullIdent(startingDot);
201         final String importText = name.getText();
202         final boolean isStarImport = importText.endsWith(STAR_IMPORT_SUFFIX);
203         if (isStarImport) {
204             currentStarImportsCount++;
205             if (currentStarImportsCount > maxAllowedStarImports
206                     && !excludes.contains(importText)) {
207                 if (maxAllowedStarImports > 0) {
208                     log(startingDot, MSG_COUNT, maxAllowedStarImports);
209                 }
210                 else {
211                     log(startingDot, MSG_KEY, importText);
212                 }
213             }
214         }
215     }
216 }