Add Spring Checkstyle with all checks disabled

Introduce checkstyle rules from spring-javaformat, but keep them
disabled so that fixes can be introduced one commit at a time.

Issue gh-8945

build.gradle

@@ -42,9 +42,22 @@ subprojects {
 
 allprojects {
 	apply plugin: 'io.spring.javaformat'
+	apply plugin: 'checkstyle'
+
+	pluginManager.withPlugin("io.spring.convention.checkstyle", { plugin ->
+		configure(plugin) {
+			dependencies {
+				checkstyle "io.spring.javaformat:spring-javaformat-checkstyle:$springJavaformatVersion"
+			}
+			checkstyle {
+				toolVersion = '8.34'
+			}
+		}
+	})
+
 	if (project.name.contains('sample')) {
 		tasks.whenTaskAdded { task ->
-			if (task.name.contains('format') || task.name.contains('checkFormat')) {
+			if (task.name.contains('format') || task.name.contains('checkFormat') || task.name.contains("checkstyle")) {
 				task.enabled = false
 			}
 		}

etc/checkstyle/checkstyle-suppressions.xml

@@ -0,0 +1,47 @@
+<?xml version="1.0"?>
+<!DOCTYPE suppressions PUBLIC
+		"-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
+		"https://checkstyle.org/dtds/suppressions_1_2.dtd">
+<suppressions>
+	<suppress files=".*" checks="AnnotationUseStyle" />
+	<suppress files=".*" checks="ArrayTypeStyle" />
+	<suppress files=".*" checks="AtclauseOrder" />
+	<suppress files=".*" checks="AvoidStarImport" />
+	<suppress files=".*" checks="EmptyBlock" />
+	<suppress files=".*" checks="FinalClass" />
+	<suppress files=".*" checks="InnerAssignment" />
+	<suppress files=".*" checks="InnerTypeLast" />
+	<suppress files=".*" checks="InterfaceIsType" />
+	<suppress files=".*" checks="JavadocMethod" />
+	<suppress files=".*" checks="JavadocStyle" />
+	<suppress files=".*" checks="JavadocTagContinuationIndentation" />
+	<suppress files=".*" checks="JavadocType" />
+	<suppress files=".*" checks="JavadocVariable" />
+	<suppress files=".*" checks="ModifierOrder" />
+	<suppress files=".*" checks="MultipleVariableDeclarations" />
+	<suppress files=".*" checks="MutableException" />
+	<suppress files=".*" checks="NeedBraces" />
+	<suppress files=".*" checks="NestedIfDepth" />
+	<suppress files=".*" checks="NewlineAtEndOfFile" />
+	<suppress files=".*" checks="NonEmptyAtclauseDescription" />
+	<suppress files=".*" checks="NoWhitespaceBefore" />
+	<suppress files=".*" checks="OneTopLevelClass" />
+	<suppress files=".*" checks="ParenPad" />
+	<suppress files=".*" checks="RedundantImport" />
+	<suppress files=".*" checks="RegexpSinglelineJava" />
+	<suppress files=".*" checks="RequireThis" />
+	<suppress files=".*" checks="SimplifyBooleanExpression" />
+	<suppress files=".*" checks="SimplifyBooleanReturn" />
+	<suppress files=".*" checks="SpringAvoidStaticImport" />
+	<suppress files=".*" checks="SpringCatch" />
+	<suppress files=".*" checks="SpringHeader" />
+	<suppress files=".*" checks="SpringHideUtilityClassConstructor" />
+	<suppress files=".*" checks="SpringImportOrder" />
+	<suppress files=".*" checks="SpringJavadoc" />
+	<suppress files=".*" checks="SpringLambda" />
+	<suppress files=".*" checks="SpringMethodOrder" />
+	<suppress files=".*" checks="SpringMethodVisibility" />
+	<suppress files=".*" checks="SpringTernary" />
+	<suppress files=".*" checks="WhitespaceAfter" />
+	<suppress files=".*" checks="WhitespaceAround" />
+</suppressions>

etc/checkstyle/checkstyle.xml

@@ -1,51 +1,11 @@
 <?xml version="1.0"?>
-<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
-		"https://www.puppycrawl.com/dtds/configuration_1_3.dtd">
-<module name="Checker">
-	<!-- Suppressions -->
+<!DOCTYPE module PUBLIC
+		"-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+		"https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="com.puppycrawl.tools.checkstyle.Checker">
 	<module name="SuppressionFilter">
-		<property name="file" value="${config_loc}/suppressions.xml"/>
+		<property name="file"
+			value="${config_loc}/checkstyle-suppressions.xml" />
 	</module>
-
-	<!-- Root Checks -->
-	<module name="RegexpHeader">
-		<property name="headerFile" value="${config_loc}/header.txt"/>
-		<property name="fileExtensions" value="java"/>
-	</module>
-
-	<!-- Root Checks -->
-	<module name="TreeWalker">
-		<!-- Annotations -->
-		<module name="MissingOverrideCheck" />
-
-		<!-- Coding -->
-		<module name="EmptyStatementCheck" />
-		<module name="RedundantModifier" />
-
-		<!-- Imports -->
-		<module name="UnusedImportsCheck">
-			<property name="processJavadoc" value="true" />
-		</module>
-
-		<!-- Regexp -->
-		<module name="RegexpSinglelineJava">
-			<property name="format" value="^\t* +\t*\S"/>
-			<property name="message" value="Line has leading space characters; indentation should be performed with tabs only."/>
-			<property name="ignoreComments" value="true"/>
-		</module>
-		<module name="RegexpSinglelineJava">
-			<property name="maximum" value="0"/>
-			<property name="format" value="org\.junit\.Assert\.assert"/>
-			<property name="message" value="Please use AssertJ imports."/>
-			<property name="ignoreComments" value="true"/>
-		</module>
-		<module name="Regexp">
-			<property name="format" value="[ \t]+$"/>
-			<property name="illegalPattern" value="true"/>
-			<property name="message" value="Trailing whitespace"/>
-		</module>
-
-		<!-- Whitespace -->
-		<module name="WhitespaceAfterCheck" />
-	</module>
-</module>
+	<module name="io.spring.javaformat.checkstyle.SpringChecks" />
+</module>

etc/checkstyle/header.txt

@@ -1,16 +0,0 @@
-^\Q/*\E$
-^\Q * Copyright\E (\d{4}(\-\d{4})? the original author or authors\.|(\d{4}, )*(\d{4}) Acegi Technology Pty Limited)$
-^\Q *\E$
-^\Q * Licensed under the Apache License, Version 2.0 (the "License");\E$
-^\Q * you may not use this file except in compliance with the License.\E$
-^\Q * You may obtain a copy of the License at\E$
-^\Q *\E$
-^\Q *      https://www.apache.org/licenses/LICENSE-2.0\E$
-^\Q *\E$
-^\Q * Unless required by applicable law or agreed to in writing, software\E$
-^\Q * distributed under the License is distributed on an "AS IS" BASIS,\E$
-^\Q * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\E$
-^\Q * See the License for the specific language governing permissions and\E$
-^\Q * limitations under the License.\E$
-^\Q */\E$
-^.*$

etc/checkstyle/suppressions.xml

@@ -1,19 +0,0 @@
-<?xml version="1.0"?>
-<!DOCTYPE suppressions PUBLIC "-//Puppy Crawl//DTD Suppressions 1.1//EN"
-		"https://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
-<suppressions>
-	<suppress files=".+Application\.java" checks="HideUtilityClassConstructor"/>
-	<suppress files=".+Configuration\.java" checks="HideUtilityClassConstructor"/>
-	<suppress files="[\\/]BCrypt(Tests)?\.java" checks="RegexpHeader"/>
-
-	<suppress files="[\\/]src[\\/]test[\\/]java[\\/]" checks="Javadoc"/>
-	<suppress files="[\\/]src[\\/]integration-test[\\/]java[\\/]" checks="Javadoc"/>
-
-	<suppress files="[\\/]docs[\\/]" checks="Javadoc"/>
-	<suppress files="[\\/]docs[\\/]" checks="CommentsIndentation"/>
-	<suppress files="[\\/]docs[\\/]" checks="InnerTypeLast"/>
-
-	<suppress files="[\\/]samples[\\/]" checks="Javadoc"/>
-	<suppress files="[\\/]samples[\\/]" checks="CommentsIndentation"/>
-	<suppress files="[\\/]samples[\\/]" checks="InnerTypeLast"/>
-</suppressions>