001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2014  Oliver Burn
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////////////////////////////////////////////////////////////////////////////////
019package com.puppycrawl.tools.checkstyle.checks.imports;
020
021import com.puppycrawl.tools.checkstyle.api.Check;
022import com.puppycrawl.tools.checkstyle.api.DetailAST;
023import com.puppycrawl.tools.checkstyle.api.FullIdent;
024import com.puppycrawl.tools.checkstyle.api.TokenTypes;
025
026/**
027 * <p>
028 * Check that finds static imports.
029 * </p>
030 * <p>
031 * Rationale: Importing static members can lead to naming conflicts
032 * between class' members. It may lead to poor code readability since it
033 * may no longer be clear what class a member resides (without looking
034 * at the import statement).
035 * </p>
036 * <p>
037 * An example of how to configure the check is:
038 * </p>
039 * <pre>
040 * &lt;module name="AvoidStaticImport"&gt;
041 *   &lt;property name="excludes"
042 *       value="java.lang.System.out,java.lang.Math.*"/&gt;
043 * &lt;/module&gt;
044 * </pre>
045 *
046 * The optional "excludes" property allows for certain classes via a star
047 * notation to be excluded such as java.lang.Math.* or specific
048 * static members to be excluded like java.lang.System.out for a variable
049 * or java.lang.Math.random for a method.
050 *
051 * <p>
052 * If you exclude a starred import on a class this automatically
053 * excludes each member individually.
054 * </p>
055 *
056 * <p>
057 * For example:
058 * Excluding java.lang.Math.* will allow the import of
059 * each static member in the Math class individually like
060 * java.lang.Math.PI
061 * </p>
062 * @author Travis Schneeberger
063 * @version 1.0
064 */
065public class AvoidStaticImportCheck
066    extends Check
067{
068    /** the classes/static members to exempt from this check. */
069    private String[] excludes = new String[0];
070
071    @Override
072    public int[] getDefaultTokens()
073    {
074        return new int[] {TokenTypes.STATIC_IMPORT};
075    }
076
077    /**
078     * Sets the list of classes or static members to be exempt from the check.
079     * @param excludes a list of fully-qualified class names/specific
080     * static members where static imports are ok
081     */
082    public void setExcludes(String[] excludes)
083    {
084        this.excludes = excludes.clone();
085    }
086
087    @Override
088    public void visitToken(final DetailAST ast)
089    {
090        final DetailAST startingDot =
091            ast.getFirstChild().getNextSibling();
092        final FullIdent name = FullIdent.createFullIdent(startingDot);
093
094        if ((null != name) && !isExempt(name.getText())) {
095            log(startingDot.getLineNo(), "import.avoidStatic", name.getText());
096        }
097    }
098
099    /**
100     * Checks if a class or static member is exempt from known excludes.
101     *
102     * @param classOrStaticMember
103     *                the class or static member
104     * @return true if except false if not
105     */
106    private boolean isExempt(String classOrStaticMember)
107    {
108        for (String exclude : excludes) {
109            if (classOrStaticMember.equals(exclude)) {
110                return true;
111            }
112            else if (exclude.endsWith(".*")) {
113                //this section allows explicit imports
114                //to be exempt when configured using
115                //a starred import
116                final String excludeMinusDotStar =
117                    exclude.substring(0, exclude.length() - 2);
118                if (classOrStaticMember.startsWith(excludeMinusDotStar)) {
119                    final String member =
120                        classOrStaticMember.substring(
121                            excludeMinusDotStar.length() + 1);
122                    //if it contains a dot then it is not a member but a package
123                    if (member.indexOf('.') == -1) {
124                        return true;
125                    }
126                }
127            }
128        }
129        return false;
130    }
131}