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 }