res/checkstyle/checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
    "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
  <!-- When adding checks, keep to the order checks are listed under         -->
  <!-- 'Standard Checks' in the Checkstyle documentation:                    -->
  <!-- http://checkstyle.sourceforge.net/config_coding.html                  -->

  <!-- Cache what has passed checkstyle -->
  <property name="cacheFile"
            value="${tomcat.output}/res/checkstyle/cachefile-checkstyle.xml"/>

  <!-- Headers -->
  <module name="RegexpHeader">
    <property name="headerFile" value="${basedir}/res/checkstyle/header-al2.txt"/>
    <property name="multiLines" value="1, 2, 3, 4"/>
    <property name="fileExtensions" value="java,xml,jsp,txt,sh,bat,properties,yaml"/>
  </module>

  <!-- Whitespace -->
  <module name="FileTabCharacter"/>
  <module name="RegexpSingleline">
    <!-- No trailing whitespace -->
    <property name="format" value="\s+$"/>
  </module>

  <module name="TreeWalker">

    <!-- Annotations -->
    <module name="AnnotationLocation"/>
    <module name="AnnotationUseStyle"/>
    <module name="MissingOverride"/>
    <module name="PackageAnnotation"/>

    <!-- Block Checks -->
    <module name="AvoidNestedBlocks">
      <property name="allowInSwitchCase" value="true"/>
    </module>
    <module name="NeedBraces"/>

    <!-- Coding -->
    <module name="IllegalInstantiation"/>

    <!-- Imports -->
    <module name="AvoidStarImport"/>
    <module name="AvoidStaticImport">
        <property name="excludes" value="org.apache.catalina.startup.SimpleHttpClient.CRLF"/>
        <property name="excludes" value="org.hamcrest.MatcherAssert.*"/>
        <property name="excludes" value="org.hamcrest.core.IsInstanceOf.*"/>
    </module>
    <module name="IllegalImport">
        <property name="illegalPkgs" value="sun,junit.framework"/>
    </module>
    <module name="ImportOrder">
        <property name="groups" value="java,javax,jakarta,org.hamcrest,org.junit,org,async,jsp2,util"/>
        <property name="ordered" value="true"/>
        <property name="separated" value="true"/>
        <property name="option" value="above"/>
    </module>
    <module name="RedundantImport"/>
    <module name="UnusedImports"/>

    <!-- Javadoc Comments -->
    <module name="InvalidJavadocPosition"/>
    <module name="JavadocBlockTagLocation"/>
    <module name="JavadocContentLocationCheck"/>
    <module name="JavadocMethod">
        <property name="accessModifiers" value="public,protected"/>
    </module>
    <module name="JavadocMissingLeadingAsterisk"/>
    <module name="JavadocMissingWhitespaceAfterAsterisk"/>
    <module name="JavadocStyle">
        <!-- Disabled. Large number of errors with minimal benefit to be gained by fixing at this time. ~1500 errors -->
        <property name="checkFirstSentence" value="false"/>
        <!-- Disabled. Large number of errors with minimal benefit to be gained by fixing at this time. ~1400 errors -->
        <property name="checkEmptyJavadoc" value="false"/>
        <!-- Does not handle HTML tags in {@code ...} correctly -->
        <property name="checkHtml" value="false"/>
    </module>
    <!-- ~9000 errors
    <module name="MissingJavadocMethod"/>
    -->
    <!-- ~1500 errors
    <module name="MissingJavadocType"/>
    -->
    <module name="NonEmptyAtclauseDescription"/>
    <!-- ~1400 errors
    <module name="RequireEmptyLineBeforeBlockTagGroup"/>
    -->
    <module name="SingleLineJavadoc"/>

    <!-- Miscellaneous -->
    <!-- ~3300 errors
    <module name="Indentation">
        <property name="lineWrappingIndentation" value="8"/>
    </module>
    -->

    <!-- Modifiers -->
    <module name="ModifierOrder"/>
    <module name="RedundantModifier"/>

    <!-- Whitespace -->
    <module name="GenericWhitespace"/>
    <module name="EmptyForInitializerPad"/>
    <module name="EmptyForIteratorPad"/>
    <!--  ~ 1000 errors
    <module name="OperatorWrap">
      <property name="option" value="eol"/>
    </module>
    -->
  </module>
</module>