CheckStyle插件

如今代码静态检查越来越重要，已经成为构建高质量软件的不可或缺的一个验证步骤。如果你使用的是java语言，那么CheckStyle则是一个利器。 CheckStyle能够帮助程序员检查代码是否符合制定的规范。通过将CheckStyle的检查引入到项目构建中，可以强制让项目中的所有的开发者遵循制定规范，而不是仅仅停留在纸面上。如果发现代码违反了标准，比如类名未以大写开头、单个方法超过了指定行数、甚至单个方法抛出了3个以上的异常等。这些检查由于是基于源码的，所以不需要编译，执行速度快。

CheckStyle有针对不同IDE和构建工具的各种插件，方便开发者随时随地对代码进行静态检查。下面就讲解下如何将CheckStyle引入到maven构建中。

配置CheckStyle插件

在maven中一个名为maven-checkstyle-plugin的插件，用于执行CheckStyle task。下面是一个简单的配置。

<plugin>

    <groupId>org.apache.maven.plugins</groupId>

    <artifactId>maven-checkstyle-plugin</artifactId>

    <version>2.10</version>

    <executions>

        <execution>

            <id>checkstyle</id>

            <phase>validate</phase>

            <goals>

                <goal>check</goal>

            </goals>

            <configuration>

                <failOnViolation>true</failOnViolation>

            </configuration>

        </execution>

    </executions>

</plugin>

我们定义了在maven lifecycle的validate阶段执行check task，并且如果发现有违反标准的情况就会fail当前的build。

maven-checkstyle-plugin内置了4种规范.

config/sun_checks.xml
config/maven_checks.xml
config/turbine_checks.xml
config/avalon_checks.xml

其中sun_checks.xml为默认值。如果想要使用其他三种规范，则只需配置configuration。下面是使用maven_checks.xml的示例。

<plugin>

    <groupId>org.apache.maven.plugins</groupId>

    <artifactId>maven-checkstyle-plugin</artifactId>

    <version>2.10</version>

    <configuration>

        <configLocation>config/maven_checks.xml</configLocation>

    </configuration>

    <executions>

        <execution>

            <id>checkstyle</id>

            <phase>validate</phase>

            <goals>

                <goal>check</goal>

            </goals>

            <configuration>

                <failOnViolation>true</failOnViolation>

            </configuration>

        </execution>

    </executions>

</plugin>

自定义规范文件

我们可以使用默认的规范未见，当然也支持自定义。下面是google的一个checkstyle规范文件。

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE module PUBLIC

        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"

        "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

<!-- This is a checkstyle configuration file. For descriptions of

what the following rules do, please see the checkstyle configuration

page at http://checkstyle.sourceforge.net/config.html -->

<module name="Checker">

    <module name="RegexpSingleline">

        <!-- Requires a Google copyright notice in each file.

          Code intended to be open-sourced may have a multi-line copyright

          notice, so that this required text appears on the second line:

          <pre>

            /*

             * Copyright 2008 Google Inc.

             *

             * (details of open-source license...)

          </pre>

        -->

        <property name="format"

                  value="^(//| \*) Copyright (\([cC]\) )?[\d]{4}(\-[\d]{4})? (Google Inc\.).*$" />

        <property name="minimum" value="1" />

        <property name="maximum" value="10" />

        <property name="message" value="Google copyright is missing or malformed." />

        <property name="severity" value="error" />

    </module>

    <module name="FileTabCharacter">

        <!-- Checks that there are no tab characters in the file.

        -->

    </module>

    <module name="NewlineAtEndOfFile"/>

    <module name="RegexpSingleline">

        <!-- Checks that FIXME is not used in comments.  TODO is preferred.

        -->

        <property name="format" value="((//.*)|(\*.*))FIXME" />

        <property name="message" value='TODO is preferred to FIXME.  e.g. "TODO(johndoe): Refactor when v2 is released."' />

    </module>

    <module name="RegexpSingleline">

        <!-- Checks that TODOs are named.  (Actually, just that they are followed

             by an open paren.)

        -->

        <property name="format" value="((//.*)|(\*.*))TODO[^(]" />

        <property name="message" value='All TODOs should be named.  e.g. "TODO(johndoe): Refactor when v2 is released."' />

    </module>

    <!-- All Java AST specific tests live under TreeWalker module. -->

    <module name="TreeWalker">

        <!--

        IMPORT CHECKS

        -->

        <module name="RedundantImport">

            <!-- Checks for redundant import statements. -->

            <property name="severity" value="error"/>

        </module>

        <module name="ImportOrder">

            <!-- Checks for out of order import statements. -->

            <property name="severity" value="warning"/>

            <property name="groups" value="com.google,android,junit,net,org,java,javax"/>

            <!-- This ensures that static imports go first. -->

            <property name="option" value="top"/>

            <property name="tokens" value="STATIC_IMPORT, IMPORT"/>

        </module>

        <!--

        JAVADOC CHECKS

        -->

        <!-- Checks for Javadoc comments.                     -->

        <!-- See http://checkstyle.sf.net/config_javadoc.html -->

        <module name="JavadocMethod">

            <property name="scope" value="protected"/>

            <property name="severity" value="warning"/>

            <property name="allowMissingJavadoc" value="true"/>

            <property name="allowMissingParamTags" value="true"/>

            <property name="allowMissingReturnTag" value="true"/>

            <property name="allowMissingThrowsTags" value="true"/>

            <property name="allowThrowsTagsForSubclasses" value="true"/>

            <property name="allowUndeclaredRTE" value="true"/>

        </module>

        <module name="JavadocType">

            <property name="scope" value="protected"/>

            <property name="severity" value="error"/>

        </module>

        <module name="JavadocStyle">

            <property name="severity" value="warning"/>

        </module>

        <!--

        NAMING CHECKS

        -->

        <!-- Item 38 - Adhere to generally accepted naming conventions -->

        <module name="PackageName">

            <!-- Validates identifiers for package names against the

              supplied expression. -->

            <!-- Here the default checkstyle rule restricts package name parts to

              seven characters, this is not in line with common practice at Google.

            -->

            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>

            <property name="severity" value="warning"/>

        </module>

        <module name="TypeNameCheck">

            <!-- Validates static, final fields against the

            expression "^[A-Z][a-zA-Z0-9]*$". -->

            <metadata name="altname" value="TypeName"/>

            <property name="severity" value="warning"/>

        </module>

        <module name="ConstantNameCheck">

            <!-- Validates non-private, static, final fields against the supplied

            public/package final fields "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$". -->

            <metadata name="altname" value="ConstantName"/>

            <property name="applyToPublic" value="true"/>

            <property name="applyToProtected" value="true"/>

            <property name="applyToPackage" value="true"/>

            <property name="applyToPrivate" value="false"/>

            <property name="format" value="^([A-Z][A-Z0-9]*(_[A-Z0-9]+)*|FLAG_.*)$"/>

            <message key="name.invalidPattern"

                     value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)."/>

            <property name="severity" value="warning"/>

        </module>

        <module name="StaticVariableNameCheck">

            <!-- Validates static, non-final fields against the supplied

            expression "^[a-z][a-zA-Z0-9]*_?$". -->

            <metadata name="altname" value="StaticVariableName"/>

            <property name="applyToPublic" value="true"/>

            <property name="applyToProtected" value="true"/>

            <property name="applyToPackage" value="true"/>

            <property name="applyToPrivate" value="true"/>

            <property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>

            <property name="severity" value="warning"/>

        </module>

        <module name="MemberNameCheck">

            <!-- Validates non-static members against the supplied expression. -->

            <metadata name="altname" value="MemberName"/>

            <property name="applyToPublic" value="true"/>

            <property name="applyToProtected" value="true"/>

            <property name="applyToPackage" value="true"/>

            <property name="applyToPrivate" value="true"/>

            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>

            <property name="severity" value="warning"/>

        </module>

        <module name="MethodNameCheck">

            <!-- Validates identifiers for method names. -->

            <metadata name="altname" value="MethodName"/>

            <property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*$"/>

            <property name="severity" value="warning"/>

        </module>

        <module name="ParameterName">

            <!-- Validates identifiers for method parameters against the

              expression "^[a-z][a-zA-Z0-9]*$". -->

            <property name="severity" value="warning"/>

        </module>

        <module name="LocalFinalVariableName">

            <!-- Validates identifiers for local final variables against the

              expression "^[a-z][a-zA-Z0-9]*$". -->

            <property name="severity" value="warning"/>

        </module>

        <module name="LocalVariableName">

            <!-- Validates identifiers for local variables against the

              expression "^[a-z][a-zA-Z0-9]*$". -->

            <property name="severity" value="warning"/>

        </module>

        <!--

        LENGTH and CODING CHECKS

        -->

        <module name="LineLength">

            <!-- Checks if a line is too long. -->

            <property name="max" value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.max}" default="100"/>

            <property name="severity" value="error"/>

            <!--

              The default ignore pattern exempts the following elements:

                - import statements

                - long URLs inside comments

            -->

            <property name="ignorePattern"

                      value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.ignorePattern}"

                      default="^(package .*;\s*)|(import .*;\s*)|( *\* *https?://.*)$"/>

        </module>

        <module name="LeftCurly">

            <!-- Checks for placement of the left curly brace ('{'). -->

            <property name="severity" value="warning"/>

        </module>

        <module name="RightCurly">

            <!-- Checks right curlies on CATCH, ELSE, and TRY blocks are on

            the same line. e.g., the following example is fine:

            <pre>

              if {

                ...

              } else

            </pre>

            -->

            <!-- This next example is not fine:

            <pre>

              if {

                ...

              }

              else

            </pre>

            -->

            <property name="option" value="same"/>

            <property name="severity" value="warning"/>

        </module>

        <!-- Checks for braces around if and else blocks -->

        <module name="NeedBraces">

            <property name="severity" value="warning"/>

            <property name="tokens" value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>

        </module>

        <module name="UpperEll">

            <!-- Checks that long constants are defined with an upper ell.-->

            <property name="severity" value="error"/>

        </module>

        <module name="FallThrough">

            <!-- Warn about falling through to the next case statement.  Similar to

            javac -Xlint:fallthrough, but the check is suppressed if a single-line comment

            on the last non-blank line preceding the fallen-into case contains 'fall through' (or

            some other variants which we don't publicized to promote consistency).

            -->

            <property name="reliefPattern"

                      value="fall through|Fall through|fallthru|Fallthru|falls through|Falls through|fallthrough|Fallthrough|No break|NO break|no break|continue on"/>

            <property name="severity" value="error"/>

        </module>

        <!--

        MODIFIERS CHECKS

        -->

        <module name="ModifierOrder">

            <!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and

                 8.4.3.  The prescribed order is:

                 public, protected, private, abstract, static, final, transient, volatile,

                 synchronized, native, strictfp

              -->

        </module>

        <!--

        WHITESPACE CHECKS

        -->

        <module name="WhitespaceAround">

            <!-- Checks that various tokens are surrounded by whitespace.

                 This includes most binary operators and keywords followed

                 by regular or curly braces.

            -->

            <property name="tokens" value="ASSIGN, BAND, BAND_ASSIGN, BOR,

        BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN,

        EQUAL, GE, GT, LAND, LE, 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,

        SL, SL_ASSIGN, SR_ASSIGN, STAR, STAR_ASSIGN"/>

            <property name="severity" value="error"/>

        </module>

        <module name="WhitespaceAfter">

            <!-- Checks that commas, semicolons and typecasts are followed by

                 whitespace.

            -->

            <property name="tokens" value="COMMA, SEMI, TYPECAST"/>

        </module>

        <module name="NoWhitespaceAfter">

            <!-- Checks that there is no whitespace after various unary operators.

                 Linebreaks are allowed.

            -->

            <property name="tokens" value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS,

        UNARY_PLUS"/>

            <property name="allowLineBreaks" value="true"/>

            <property name="severity" value="error"/>

        </module>

        <module name="NoWhitespaceBefore">

            <!-- Checks that there is no whitespace before various unary operators.

                 Linebreaks are allowed.

            -->

            <property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC"/>

            <property name="allowLineBreaks" value="true"/>

            <property name="severity" value="error"/>

        </module>

        <module name="ParenPad">

            <!-- Checks that there is no whitespace before close parens or after

                 open parens.

            -->

            <property name="severity" value="warning"/>

        </module>

    </module>

</module>

如果想启用自定义的规范文件，则依旧是修改configuration，指向你的文件地址。

        <plugin>

            <groupId>org.apache.maven.plugins</groupId>

            <artifactId>maven-checkstyle-plugin</artifactId>

            <version>2.10</version>

            <configuration>

                <configLocation>${basedir}/src/config/custom_checkstyle.xml</configLocation>

            </configuration>

            <executions>

                <execution>

                    <id>checkstyle</id>

                    <phase>validate</phase>

                    <goals>

                        <goal>check</goal>

                    </goals>

                    <configuration>

                        <failOnViolation>true</failOnViolation>

                    </configuration>

                </execution>

            </executions>

        </plugin>

运行checkstyle检查

1	`mvn checkstyle:checkstyle`

查看checkstyle结果

运行maven命令后可以在console里查看checkstyle运行结果。

[INFO]

[INFO] There are 11 checkstyle errors.

[INFO] ------------------------------------------------------------------------

[INFO] BUILD FAILURE

[INFO] ------------------------------------------------------------------------

[INFO] Total time: 2.135s

[INFO] Finished at: Fri Jun 21 13:39:24 CST 2013

[INFO] Final Memory: 6M/81M

[INFO] ------------------------------------------------------------------------

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:2.10:check (checkstyle) on project SpringMessageSpike: You have 11 Checkstyle violations. -> [Help 1]

checkstye的详细结果信息被存放在target/checkstyle-result.xml中。下面是一个示例。

<?xml version="1.0" encoding="UTF-8"?>

<checkstyle version="5.6">

<file name="/Users/twer/sourcecode/SpringMessageSpike/src/main/java/com/thoughtworks/config/SessionMessageSource.java">

<error line="0" severity="error" message="Google copyright is missing or malformed." source="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineCheck"/>

<error line="21" severity="warning" message="Wrong order for &apos;org.slf4j.LoggerFactory.getLogger&apos; import." source="com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck"/>

<error line="27" severity="error" message="Missing a Javadoc comment." source="com.puppycrawl.tools.checkstyle.checks.javadoc.JavadocTypeCheck"/>

<error line="35" severity="error" message="Line is longer than 100 characters (found 115)." source="com.puppycrawl.tools.checkstyle.checks.sizes.LineLengthCheck"/>

</file>

</checkstyle>

跳过对指定文件的某些检查

如果对于指定文件检查出了一些问题，但是你想忽略它，则可以使用suppression。

例如在上述例子中有一个checkstyle error是说某行超过了100字符。如果我们不想修复这个错误怎么办那？可以将其suppress掉。

方法是建立一个checkstyle-suppressions.xml文件。其中加入下述内容

checkstyle-suppressions.xml

<?xml version="1.0"?>

<!DOCTYPE suppressions PUBLIC

        "-//Puppy Crawl//DTD Suppressions 1.0//EN"

        "http://www.puppycrawl.com/dtds/suppressions_1_0.dtd">

<suppressions>

    <suppress checks="LineLengthCheck"

              files="SessionMessageSource.java"

              />

</suppressions>

然后配置maven-checkstyel-plugin设置suppressionsLocation。

<plugin>

    <groupId>org.apache.maven.plugins</groupId>

    <artifactId>maven-checkstyle-plugin</artifactId>

    <version>2.10</version>

    <configuration>

        <configLocation>${basedir}/src/config/custom_checkstyle.xml</configLocation>

        <suppressionsLocation>${basedir}/src/config/checkstyle-suppressions.xml</suppressionsLocation>

    </configuration>

    <executions>

        <execution>

            <id>checkstyle</id>

            <phase>validate</phase>

            <goals>

                <goal>check</goal>

            </goals>

            <configuration>

                <failOnViolation>true</failOnViolation>

            </configuration>

        </execution>

    </executions>

</plugin>