001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2024 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.imports;
021
022import com.puppycrawl.tools.checkstyle.StatelessCheck;
023import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.api.FullIdent;
026import com.puppycrawl.tools.checkstyle.api.TokenTypes;
027import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
028
029/**
030 * <p>
031 * Checks that there are no static import statements.
032 * </p>
033 * <p>
034 * Rationale: Importing static members can lead to naming conflicts
035 * between class' members. It may lead to poor code readability since it
036 * may no longer be clear what class a member resides in (without looking
037 * at the import statement).
038 * </p>
039 * <p>
040 * If you exclude a starred import on a class this automatically excludes
041 * each member individually.
042 * </p>
043 * <p>
044 * For example: Excluding {@code java.lang.Math.*}. will allow the import
045 * of each static member in the Math class individually like
046 * {@code java.lang.Math.PI, java.lang.Math.cos, ...}.
047 * </p>
048 * <ul>
049 * <li>
050 * Property {@code excludes} - Control whether to allow for certain classes via
051 * a star notation to be excluded such as {@code java.lang.Math.*} or specific
052 * static members to be excluded like {@code java.lang.System.out} for a variable
053 * or {@code java.lang.Math.random} for a method. See notes section for details.
054 * Type is {@code java.lang.String[]}.
055 * Default value is {@code ""}.
056 * </li>
057 * </ul>
058 * <p>
059 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
060 * </p>
061 * <p>
062 * Violation Message Keys:
063 * </p>
064 * <ul>
065 * <li>
066 * {@code import.avoidStatic}
067 * </li>
068 * </ul>
069 *
070 * @since 5.0
071 */
072@StatelessCheck
073public class AvoidStaticImportCheck
074    extends AbstractCheck {
075
076    /**
077     * A key is pointing to the warning message text in "messages.properties"
078     * file.
079     */
080    public static final String MSG_KEY = "import.avoidStatic";
081
082    /**
083     * Control whether to allow for certain classes via a star notation to be
084     * excluded such as {@code java.lang.Math.*} or specific static members
085     * to be excluded like {@code java.lang.System.out} for a variable or
086     * {@code java.lang.Math.random} for a method. See notes section for details.
087     */
088    private String[] excludes = CommonUtil.EMPTY_STRING_ARRAY;
089
090    @Override
091    public int[] getDefaultTokens() {
092        return getRequiredTokens();
093    }
094
095    @Override
096    public int[] getAcceptableTokens() {
097        return getRequiredTokens();
098    }
099
100    @Override
101    public int[] getRequiredTokens() {
102        return new int[] {TokenTypes.STATIC_IMPORT};
103    }
104
105    /**
106     * Setter to control whether to allow for certain classes via a star notation
107     * to be excluded such as {@code java.lang.Math.*} or specific static members
108     * to be excluded like {@code java.lang.System.out} for a variable or
109     * {@code java.lang.Math.random} for a method. See notes section for details.
110     *
111     * @param excludes fully-qualified class names/specific
112     *     static members where static imports are ok
113     * @since 5.0
114     */
115    public void setExcludes(String... excludes) {
116        this.excludes = excludes.clone();
117    }
118
119    @Override
120    public void visitToken(final DetailAST ast) {
121        final DetailAST startingDot =
122            ast.getFirstChild().getNextSibling();
123        final FullIdent name = FullIdent.createFullIdent(startingDot);
124
125        final String nameText = name.getText();
126        if (!isExempt(nameText)) {
127            log(startingDot, MSG_KEY, nameText);
128        }
129    }
130
131    /**
132     * Checks if a class or static member is exempt from known excludes.
133     *
134     * @param classOrStaticMember
135     *                the class or static member
136     * @return true if except false if not
137     */
138    private boolean isExempt(String classOrStaticMember) {
139        boolean exempt = false;
140
141        for (String exclude : excludes) {
142            if (classOrStaticMember.equals(exclude)
143                    || isStarImportOfPackage(classOrStaticMember, exclude)) {
144                exempt = true;
145                break;
146            }
147        }
148        return exempt;
149    }
150
151    /**
152     * Returns true if classOrStaticMember is a starred name of package,
153     *  not just member name.
154     *
155     * @param classOrStaticMember - full name of member
156     * @param exclude - current exclusion
157     * @return true if member in exclusion list
158     */
159    private static boolean isStarImportOfPackage(String classOrStaticMember, String exclude) {
160        boolean result = false;
161        if (exclude.endsWith(".*")) {
162            // this section allows explicit imports
163            // to be exempt when configured using
164            // a starred import
165            final String excludeMinusDotStar =
166                exclude.substring(0, exclude.length() - 2);
167            if (classOrStaticMember.startsWith(excludeMinusDotStar)
168                    && !classOrStaticMember.equals(excludeMinusDotStar)) {
169                final String member = classOrStaticMember.substring(
170                        excludeMinusDotStar.length() + 1);
171                // if it contains a dot then it is not a member but a package
172                if (member.indexOf('.') == -1) {
173                    result = true;
174                }
175            }
176        }
177        return result;
178    }
179
180}