代码规约

为了在提交代码之前做一些必要的代码检查，我们需要使用一些工具来辅助我们的工作——对于maven工程我们可以使用maven checkstyle plugin

1.插件配置

pom文件

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-checkstyle-plugin</artifactId>
  <version>3.0.0</version>
  <configuration>
    <configLocation>xinniu-java-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>

checkstyle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">
    <!--
    LENGTH and CODING CHECKS
    -->
    <module name="FileTabCharacter">
        <!-- 代码缩进用4个空格代替tab
        -->
    </module>
    <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">
        <module name="LineLength">
            <!-- 代码列宽: 统一设置列宽120，避免单行代码太长 -->
            <property name="max" value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.max}" default="120"/>
            <property name="severity" value="error"/>
            <!--
              The default ignore pattern exempts the following elements:
                - import statements
                - long URLs inside comments
            -->
            <property name="ignorePattern"
                      value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.ignorePattern}"
                      default="^(package .*;\s*)|(import .*;\s*)|( *\* *https?://.*)$"/>
        </module>
        <!--
        IMPORT CHECKS
        -->
        <module name="RedundantImport">
            <!-- Checks for redundant import statements. -->
            <property name="severity" value="error"/>
        </module>
        <module name="ImportOrder">
            <!-- Checks for out of order import statements. -->
            <property name="severity" value="warning"/>
            <property name="groups" value="com.google,android,junit,net,org,java,javax"/>
            <!-- This ensures that static imports go first. -->
            <property name="option" value="top"/>
            <property name="tokens" value="STATIC_IMPORT, IMPORT"/>
        </module>
        <!--
        NAMING CHECKS
        -->
        <!-- Item 38 - Adhere to generally accepted naming conventions -->
        <module name="PackageName">
            <!-- Validates identifiers for package names against the
              supplied expression. -->
            <!-- Here the default checkstyle rule restricts package name parts to
              seven characters, this is not in line with common practice at Google.
            -->
            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>
            <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>
        <!-- {}在使用时，左括号在代码块起始行行尾，右括号与代码块起始行上下对齐，与if, else, for, do, while等配合使用 -->
        <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">
        </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>

2.运行mvn命令检测代码

1. 首先执行mvn checkstyle:checkstyle命令检查工程是否满足checkstyle。方法右键pom.xml文件，选择run as-->选择第二个maven build，在Goals中输入checkstyle:checkstyle（最好在Name中取个名字，方便复用），点击Run即可，具体的检测结果可以在taget\checkstyle-result中查看
2. 执行mvn jxr:jxr命令可以查看有错的对应代码