AvoidStaticImportCheck.java
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2021 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks.imports;
import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.FullIdent;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
/**
* <p>
* Checks that there are no static import statements.
* </p>
* <p>
* Rationale: Importing static members can lead to naming conflicts
* between class' members. It may lead to poor code readability since it
* may no longer be clear what class a member resides in (without looking
* at the import statement).
* </p>
* <p>
* If you exclude a starred import on a class this automatically excludes
* each member individually.
* </p>
* <p>
* For example: Excluding {@code java.lang.Math.*}. will allow the import
* of each static member in the Math class individually like
* {@code java.lang.Math.PI, java.lang.Math.cos, ...}.
* </p>
* <ul>
* <li>
* Property {@code excludes} - Control whether to allow for certain classes via
* a star notation to be excluded such as {@code java.lang.Math.*} or specific
* static members to be excluded like {@code java.lang.System.out} for a variable
* or {@code java.lang.Math.random} for a method. See notes section for details.
* Type is {@code java.lang.String[]}.
* Default value is {@code ""}.
* </li>
* </ul>
* <p>
* To configure the check:
* </p>
* <pre>
* <module name="AvoidStaticImport"/>
* </pre>
* <p>Example:</p>
* <pre>
* import static java.lang.Math.pow; // violation
* import static java.lang.System.*; // violation
* import java.io.File; // OK
* import java.util.*; // OK
* </pre>
* <p>
* To configure the check so that the {@code java.lang.System.out} member and all
* members from {@code java.lang.Math} are allowed:
* </p>
* <pre>
* <module name="AvoidStaticImport">
* <property name="excludes" value="java.lang.System.out,java.lang.Math.*"/>
* </module>
* </pre>
* <p>Example:</p>
* <pre>
* import static java.lang.Math.*; // OK
* import static java.lang.System.out; // OK
* import static java.lang.Integer.parseInt; // violation
* import java.io.*; // OK
* import java.util.*; // OK
* </pre>
* <p>
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
* </p>
* <p>
* Violation Message Keys:
* </p>
* <ul>
* <li>
* {@code import.avoidStatic}
* </li>
* </ul>
*
* @since 5.0
*/
@StatelessCheck
public class AvoidStaticImportCheck
extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "import.avoidStatic";
/**
* Control whether to allow for certain classes via a star notation to be
* excluded such as {@code java.lang.Math.*} or specific static members
* to be excluded like {@code java.lang.System.out} for a variable or
* {@code java.lang.Math.random} for a method. See notes section for details.
*/
private String[] excludes = CommonUtil.EMPTY_STRING_ARRAY;
@Override
public int[] getDefaultTokens() {
return getRequiredTokens();
}
@Override
public int[] getAcceptableTokens() {
return getRequiredTokens();
}
@Override
public int[] getRequiredTokens() {
return new int[] {TokenTypes.STATIC_IMPORT};
}
/**
* Setter to control whether to allow for certain classes via a star notation
* to be excluded such as {@code java.lang.Math.*} or specific static members
* to be excluded like {@code java.lang.System.out} for a variable or
* {@code java.lang.Math.random} for a method. See notes section for details.
*
* @param excludes a list of fully-qualified class names/specific
* static members where static imports are ok
*/
public void setExcludes(String... excludes) {
this.excludes = excludes.clone();
}
@Override
public void visitToken(final DetailAST ast) {
final DetailAST startingDot =
ast.getFirstChild().getNextSibling();
final FullIdent name = FullIdent.createFullIdent(startingDot);
if (!isExempt(name.getText())) {
log(startingDot, MSG_KEY, name.getText());
}
}
/**
* Checks if a class or static member is exempt from known excludes.
*
* @param classOrStaticMember
* the class or static member
* @return true if except false if not
*/
private boolean isExempt(String classOrStaticMember) {
boolean exempt = false;
for (String exclude : excludes) {
if (classOrStaticMember.equals(exclude)
|| isStarImportOfPackage(classOrStaticMember, exclude)) {
exempt = true;
break;
}
}
return exempt;
}
/**
* Returns true if classOrStaticMember is a starred name of package,
* not just member name.
*
* @param classOrStaticMember - full name of member
* @param exclude - current exclusion
* @return true if member in exclusion list
*/
private static boolean isStarImportOfPackage(String classOrStaticMember, String exclude) {
boolean result = false;
if (exclude.endsWith(".*")) {
// this section allows explicit imports
// to be exempt when configured using
// a starred import
final String excludeMinusDotStar =
exclude.substring(0, exclude.length() - 2);
if (classOrStaticMember.startsWith(excludeMinusDotStar)
&& !classOrStaticMember.equals(excludeMinusDotStar)) {
final String member = classOrStaticMember.substring(
excludeMinusDotStar.length() + 1);
// if it contains a dot then it is not a member but a package
if (member.indexOf('.') == -1) {
result = true;
}
}
}
return result;
}
}