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 /**
99 * Creates a new {@code AvoidStarImportCheck} instance.
100 */
101 public AvoidStarImportCheck() {
102 // no code by default
103 }
104
105 @Override
106 public int[] getDefaultTokens() {
107 return getRequiredTokens();
108 }
109
110 @Override
111 public int[] getAcceptableTokens() {
112 return getRequiredTokens();
113 }
114
115 @Override
116 public int[] getRequiredTokens() {
117 // original implementation checks both IMPORT and STATIC_IMPORT tokens to avoid ".*" imports
118 // however user can allow using "import" or "import static"
119 // by configuring allowClassImports and allowStaticMemberImports
120 // To avoid potential confusion when user specifies conflicting options on configuration
121 // (see example below) we are adding both tokens to Required list
122 // <module name="AvoidStarImport">
123 // <property name="tokens" value="IMPORT"/>
124 // <property name="allowStaticMemberImports" value="false"/>
125 // </module>
126 return new int[] {TokenTypes.IMPORT, TokenTypes.STATIC_IMPORT};
127 }
128
129 /**
130 * Setter to specify packages where starred class imports are
131 * allowed and classes where starred static member imports are allowed.
132 *
133 * @param excludesParam package names/fully-qualifies class names
134 * where star imports are ok
135 * @since 3.2
136 */
137 public void setExcludes(String... excludesParam) {
138 for (final String exclude : excludesParam) {
139 if (exclude.endsWith(STAR_IMPORT_SUFFIX)) {
140 excludes.add(exclude);
141 }
142 else {
143 excludes.add(exclude + STAR_IMPORT_SUFFIX);
144 }
145 }
146 }
147
148 /**
149 * Setter to control whether to allow starred class imports like
150 * {@code import java.util.*;}.
151 *
152 * @param allow true to allow false to disallow
153 * @since 5.3
154 */
155 public void setAllowClassImports(boolean allow) {
156 allowClassImports = allow;
157 }
158
159 /**
160 * Setter to control whether to allow starred static member imports like
161 * {@code import static org.junit.Assert.*;}.
162 *
163 * @param allow true to allow false to disallow
164 * @since 5.3
165 */
166 public void setAllowStaticMemberImports(boolean allow) {
167 allowStaticMemberImports = allow;
168 }
169
170 /**
171 * Setter to control how many star imports are allowed.
172 *
173 * @param count the number of star imports allowed
174 * @since 13.5.0
175 */
176 public void setMaxAllowedStarImports(int count) {
177 maxAllowedStarImports = count;
178 }
179
180 @Override
181 public void beginTree(DetailAST rootAST) {
182 currentStarImportsCount = 0;
183 }
184
185 @Override
186 public void visitToken(final DetailAST ast) {
187 if (ast.getType() == TokenTypes.IMPORT) {
188 if (!allowClassImports) {
189 final DetailAST startingDot = ast.getFirstChild();
190 logsStarredImportViolation(startingDot);
191 }
192 }
193 else if (!allowStaticMemberImports) {
194 // must navigate past the static keyword
195 final DetailAST startingDot = ast.getFirstChild().getNextSibling();
196 logsStarredImportViolation(startingDot);
197 }
198 }
199
200 /**
201 * Gets the full import identifier. If the import is a starred import and
202 * it's not excluded then a violation is logged.
203 *
204 * @param startingDot the starting dot for the import statement
205 */
206 private void logsStarredImportViolation(DetailAST startingDot) {
207 final FullIdent name = FullIdent.createFullIdent(startingDot);
208 final String importText = name.getText();
209 final boolean isStarImport = importText.endsWith(STAR_IMPORT_SUFFIX);
210 if (isStarImport) {
211 currentStarImportsCount++;
212 if (currentStarImportsCount > maxAllowedStarImports
213 && !excludes.contains(importText)) {
214 if (maxAllowedStarImports > 0) {
215 log(startingDot, MSG_COUNT, maxAllowedStarImports);
216 }
217 else {
218 log(startingDot, MSG_KEY, importText);
219 }
220 }
221 }
222 }
223
224 }