CheckStyle

Checkstyle is a tool for checking Code Standards Violations. It can be used different environments:

• Standalone (not covered here)
• Ant
• Maven
• IDE

Description

Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard. It automates the process of checking Java code to spare humans of this boring (but important) task. This makes it ideal for projects that want to enforce a coding standard.

Checkstyle is highly configurable and can be made to support almost any coding standard. An example configuration files are supplied supporting the Sun Code Conventions, Google Java Style.

For downloading the software see the homepage of CheckStyle on SourceForge .

Pre-requirements

• All
• Ant
  • Installed version of Apache Ant .
  • Dowloaded and installed standalone version. See the SourceForge Website of CheckStyle .
• Maven
  • Internet Connection for running Maven.
  • Installed version of Apache Maven .

Installation in Ant

To set CheckStyle in Ant add the following line of code to the build.xml. <syntaxhighlight lang="xml" line>

  <property name = "checkstyle.home.dir" location = "." />
  ...
  <taskdef resource  = "com/puppycrawl/tools/checkstyle/ant/checkstyle-ant-task.properties" classpath = "checkstyle-6.8.1-all.jar" />
  ...
  <property name="checkstyle.sourcepath"    value="src"                      />
  <property name="checkstyle.report.path"   value="."                        />
  <property name="checkstyle.report.style"  value="checkstyle-simple.xsl"    />
  <property name="checkstyle.report.xml"    value="checkstyle-report.xml"    />
  <property name="checkstyle.report.html"   value="checkstyle-report.html"   />
  ...
  <target name        = "check"
          description = "Generates a report of code convention violations.">

     <mkdir dir   = "${checkstyle.report.path}" />

     <checkstyle config          = "${checkstyle.report.config}"
                 failureProperty = "checkstyle.failure"
                 failOnViolation = "false">
        <formatter type   = "xml"
                   tofile = "${checkstyle.report.xml}"/>
        <fileset dir      = "${checkstyle.sourcepath}"
                 includes = "**/*.java, **/*.xml, **/*.properties"
                 excludes = "checkstyle/" />
     </checkstyle>
     <xslt basedir = "${checkstyle.report.path}"
           destdir = "${checkstyle.report.path}"
           style   = "${checkstyle.report.style}" />
  </target>

</syntaxhighlight>

Line	Description	Default	Global
1-2	Property for the location of all the checkstyle-jar files. It must contain checkstyle-6.8.1-all.jar (See below).	Current Directory	/usr/local/bin/checkstyle-6.8.1
4-5	Reference to the checkstyle resource	checkstyle-6.8.1-all.jar
7-12	References to the checkstyle properties.
14-36	Ant-Target definition, creating the report path, running checkstyle and formats the resulting xml-report to HTML using XSLT.

Installation in Maven

To set CheckStyle in Maven or Maven 2 add the following lines of code to the settings of the project.xml, project.properties.

Project.xml

<syntaxhighlight lang="xml">

 <reports>
    ...
    <report>maven-checkstyle-plugin</report>
    ...
 </reports>

</syntaxhighlight>

Project.properties

Add the name of the file containing the checkstyle settings: <syntaxhighlight lang="bash">

1. Checkstyle settings #

maven.checkstyle.excludes=**/*generated*/** maven.checkstyle.properties=${basedir}/AAB_checks.xml </syntaxhighlight>

Configuration

The default CheckStyle is highly configurable. The installation come with sample configuration files:

• Apache Avalon (avalon_checks.xml)
• Sun coding conventions (sun_checks.xml)
• Apache Turbine Framework (turbine_checks.xml), this is the base of Frame

The AAB uses its own CheckStyle convention (AAB_checks.xml), which is configured for each project separately. The format of the configuration file: <syntaxhighlight lang="xml"> <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.1//EN" "http://www.puppycrawl.com/dtds/configuration_1_1.dtd"> <module name="Checker">

   <module name="TreeWalker">
       <module name="com.puppycrawl.tools.checkstyle.checks.GenericIllegalRegexpCheck">
           <property name="format" value="System.err"/>
           <property name="ignoreCase" value="false"/>
           <property name="ignoreComments" value="false"/>
           <property name="message" value="Do not use System.err"/>
           <property name="severity" value="warning"/>
       </module>
       ...
       <module name="com.puppycrawl.tools.checkstyle.checks.sizes.LineLengthCheck">
           <property name="ignorePattern" value="^$"/>
           <property name="max" value="110"/>
           <property name="severity" value="warning"/>
           <property name="tabWidth" value="4"/>
       </module>
       ...
  </module>

</module> </syntaxhighlight>

Problem

The CheckStyle report becomes very long and difficult to handel. There are a few checks which delivers very much lines of report lines. A comparison of the size of checkstyle-report.html file for the different checkstyles

CheckStyle HTML-Size Kb HTML Reduction % HTML-Lines K Line Reduction % Description All 3,881  0 90,142 0,00% Default checks No LineLength 3,545  336 82,104 8.66% No com.puppycrawl.tools.checkstyle.checks.sizes.LineLengthCheck (AAB_1_checks.xml) No indentation 1,563 1,982 37,411 51.07% No com.puppycrawl.tools.checkstyle.checks.indentation.IndentationCheck (AAB_1_checks.xml) No whitespace Param Pad 1,561  2 37,378 0.05% No com.puppycrawl.tools.checkstyle.checks.whitespace.MethodParamPadCheck Tokens: CTOR_DEF, LITERAL_NEW, METHOD_CALL, METHOD_DEF, SUPER_CTOR_CALL No whitespace After 1,537  24 36,795 0.62% No com.puppycrawl.tools.checkstyle.checks.whitespace.NoWhitespaceAfterCheck Tokens: ARRAY_INIT, BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS, UNARY_PLUS No whitespace Before 1,536  1 36.773 0.03% No com.puppycrawl.tools.checkstyle.checks.whitespace.WhitespaceAfterCheck Tokens: SEMI, POST_DEC, POST_INC No whitespace After 1,058 478 25,286 12.32% No com.puppycrawl.tools.checkstyle.checks.whitespace.NoWhitespaceAfterCheck Tokens: COMMA, SEMI, TYPECAST No whitespace Around 643 415 15,276 10.69% No com.puppycrawl.tools.checkstyle.checks.whitespace.WhitespaceAroundCheck Tokens: ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN, EQUAL, GE, GT, LAND, LCURLY, LE, LITERAL_ASSERT, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN, LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS, MINUS_ASSIGN, MOD, MOD_ASSIGN, NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION, RCURLY, SL, SLIST, SL_ASSIGN, SR, SR_ASSIGN, STAR, STAR_ASSIGN

See also

• Software Static Test Software Overview contains more information on other Static Software Tools.