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 * <div> 031 * Checks that there are no static import statements. 032 * </div> 033 * 034 * <p> 035 * Rationale: Importing static members can lead to naming conflicts 036 * between class' members. It may lead to poor code readability since it 037 * may no longer be clear what class a member resides in (without looking 038 * at the import statement). 039 * </p> 040 * 041 * <p> 042 * If you exclude a starred import on a class this automatically excludes 043 * each member individually. 044 * </p> 045 * 046 * <p> 047 * For example: Excluding {@code java.lang.Math.*}. will allow the import 048 * of each static member in the Math class individually like 049 * {@code java.lang.Math.PI, java.lang.Math.cos, ...}. 050 * </p> 051 * <ul> 052 * <li> 053 * Property {@code excludes} - Control whether to allow for certain classes via 054 * a star notation to be excluded such as {@code java.lang.Math.*} or specific 055 * static members to be excluded like {@code java.lang.System.out} for a variable 056 * or {@code java.lang.Math.random} for a method. See notes section for details. 057 * Type is {@code java.lang.String[]}. 058 * Default value is {@code ""}. 059 * </li> 060 * </ul> 061 * 062 * <p> 063 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker} 064 * </p> 065 * 066 * <p> 067 * Violation Message Keys: 068 * </p> 069 * <ul> 070 * <li> 071 * {@code import.avoidStatic} 072 * </li> 073 * </ul> 074 * 075 * @since 5.0 076 */ 077@StatelessCheck 078public class AvoidStaticImportCheck 079 extends AbstractCheck { 080 081 /** 082 * A key is pointing to the warning message text in "messages.properties" 083 * file. 084 */ 085 public static final String MSG_KEY = "import.avoidStatic"; 086 087 /** 088 * Control whether to allow for certain classes via a star notation to be 089 * excluded such as {@code java.lang.Math.*} or specific static members 090 * to be excluded like {@code java.lang.System.out} for a variable or 091 * {@code java.lang.Math.random} for a method. See notes section for details. 092 */ 093 private String[] excludes = CommonUtil.EMPTY_STRING_ARRAY; 094 095 @Override 096 public int[] getDefaultTokens() { 097 return getRequiredTokens(); 098 } 099 100 @Override 101 public int[] getAcceptableTokens() { 102 return getRequiredTokens(); 103 } 104 105 @Override 106 public int[] getRequiredTokens() { 107 return new int[] {TokenTypes.STATIC_IMPORT}; 108 } 109 110 /** 111 * Setter to control whether to allow for certain classes via a star notation 112 * to be excluded such as {@code java.lang.Math.*} or specific static members 113 * to be excluded like {@code java.lang.System.out} for a variable or 114 * {@code java.lang.Math.random} for a method. See notes section for details. 115 * 116 * @param excludes fully-qualified class names/specific 117 * static members where static imports are ok 118 * @since 5.0 119 */ 120 public void setExcludes(String... excludes) { 121 this.excludes = excludes.clone(); 122 } 123 124 @Override 125 public void visitToken(final DetailAST ast) { 126 final DetailAST startingDot = 127 ast.getFirstChild().getNextSibling(); 128 final FullIdent name = FullIdent.createFullIdent(startingDot); 129 130 final String nameText = name.getText(); 131 if (!isExempt(nameText)) { 132 log(startingDot, MSG_KEY, nameText); 133 } 134 } 135 136 /** 137 * Checks if a class or static member is exempt from known excludes. 138 * 139 * @param classOrStaticMember 140 * the class or static member 141 * @return true if except false if not 142 */ 143 private boolean isExempt(String classOrStaticMember) { 144 boolean exempt = false; 145 146 for (String exclude : excludes) { 147 if (classOrStaticMember.equals(exclude) 148 || isStarImportOfPackage(classOrStaticMember, exclude)) { 149 exempt = true; 150 break; 151 } 152 } 153 return exempt; 154 } 155 156 /** 157 * Returns true if classOrStaticMember is a starred name of package, 158 * not just member name. 159 * 160 * @param classOrStaticMember - full name of member 161 * @param exclude - current exclusion 162 * @return true if member in exclusion list 163 */ 164 private static boolean isStarImportOfPackage(String classOrStaticMember, String exclude) { 165 boolean result = false; 166 if (exclude.endsWith(".*")) { 167 // this section allows explicit imports 168 // to be exempt when configured using 169 // a starred import 170 final String excludeMinusDotStar = 171 exclude.substring(0, exclude.length() - 2); 172 if (classOrStaticMember.startsWith(excludeMinusDotStar) 173 && !classOrStaticMember.equals(excludeMinusDotStar)) { 174 final String member = classOrStaticMember.substring( 175 excludeMinusDotStar.length() + 1); 176 // if it contains a dot then it is not a member but a package 177 if (member.indexOf('.') == -1) { 178 result = true; 179 } 180 } 181 } 182 return result; 183 } 184 185}