From 6819ba3726c37dd497520013f718da68eca86c6b Mon Sep 17 00:00:00 2001
From: Anton Pinsky <anton.pinsky@ionos.com>
Date: Tue, 14 Nov 2023 21:48:20 +0100
Subject: [PATCH] [#112]Introduce Checkstyle plugin; immediately got 468 errors

Signed-off-by: Anton Pinsky <anton.pinsky@ionos.com>
---
 etc/config/checkstyle-suppressions.xml |  28 +++
 etc/config/checkstyle.xml              | 248 +++++++++++++++++++++++++
 pom.xml                                |  38 ++++
 3 files changed, 314 insertions(+)
 create mode 100644 etc/config/checkstyle-suppressions.xml
 create mode 100644 etc/config/checkstyle.xml

diff --git a/etc/config/checkstyle-suppressions.xml b/etc/config/checkstyle-suppressions.xml
new file mode 100644
index 00000000..aa3e1883
--- /dev/null
+++ b/etc/config/checkstyle-suppressions.xml
@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+<!--
+
+Copyright (c) 2023 Oracle and/or its affiliates. All rights reserved.
+
+This program and the accompanying materials are made available under the
+terms of the Eclipse Public License v. 2.0, which is available at
+http://www.eclipse.org/legal/epl-2.0.
+
+This Source Code may also be made available under the following Secondary
+Licenses when the conditions for such availability set forth in the
+Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+version 2 with the GNU Classpath Exception, which is available at
+https://www.gnu.org/software/classpath/license.html.
+
+SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+
+-->
+
+<!DOCTYPE suppressions PUBLIC
+        "-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
+        "https://checkstyle.org/dtds/suppressions_1_2.dtd">
+
+<suppressions>
+    <!-- I was not able to properly set import ordering for static imports -->
+    <suppress checks="ImportOrder" message="Extra separation in import group before" />
+</suppressions>
+
diff --git a/etc/config/checkstyle.xml b/etc/config/checkstyle.xml
new file mode 100644
index 00000000..56c34127
--- /dev/null
+++ b/etc/config/checkstyle.xml
@@ -0,0 +1,248 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+Copyright (c) 2023 Oracle and/or its affiliates. All rights reserved.
+
+This program and the accompanying materials are made available under the
+terms of the Eclipse Public License v. 2.0, which is available at
+http://www.eclipse.org/legal/epl-2.0.
+
+This Source Code may also be made available under the following Secondary
+Licenses when the conditions for such availability set forth in the
+Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+version 2 with the GNU Classpath Exception, which is available at
+https://www.gnu.org/software/classpath/license.html.
+
+SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+
+-->
+
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+<!--
+    This file is based on maven-checkstyle-plugin config/sun_checks.xml file.
+    Checkstyle configuration that checks the coding conventions based on:
+      - the Java Language Specification at
+        http://java.sun.com/docs/books/jls/second_edition/html/index.html
+      - the Sun Code Conventions at http://java.sun.com/docs/codeconv/
+      - the Javadoc guidelines at
+        http://java.sun.com/j2se/javadoc/writingdoccomments/index.html
+      - the JDK Api documentation http://java.sun.com/j2se/docs/api/index.html
+      - some custom relaxations of the rules above & best practices
+    Checkstyle is very configurable. Be sure to read the documentation at
+    http://checkstyle.sf.net (or in your downloaded distribution).
+    Most Checks are configurable, be sure to consult the documentation.
+    To completely disable a check, just comment it out or delete it from the file.
+    Finally, it is worth reading the documentation.
+-->
+
+<module name="Checker">
+
+    <!-- exclude module-info.java check - checkstyle can't process it -->
+    <module name="BeforeExecutionExclusionFileFilter">
+        <property name="fileNamePattern" value="module\-info\.java$"/>
+    </module>
+
+    <!--
+        If you set the basedir property below, then all reported file
+        names will be relative to the specified directory. See
+        http://checkstyle.sourceforge.net/5.x/config.html#Checker
+        <property name="basedir" value="${basedir}"/>
+    -->
+    <property name="charset" value="UTF-8"/>
+
+    <!-- Checks that each Java package has a Javadoc file used for commenting. -->
+    <!-- See http://checkstyle.sf.net/config_javadoc.html#JavadocPackage       -->
+<!--    <module name="JavadocPackage" />-->
+
+    <!-- Checks to see if a file contains a tab character. -->
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <!--
+     Making sure we do not have @author tags in javadocs
+     There is a list of developers in pom.xml that is sufficient for our needs.
+     See https://github.com/checkstyle/checkstyle/issues/5339
+    -->
+    <module name="RegexpSingleline">
+        <!-- The '.' in id is needed, otherwise ArrayIndexOutOfBounds happens -->
+        <property name="id" value="Javadoc.javadocNoAuthor"/>
+        <property name="format" value="^\s*\*\s*@author"/>
+        <property name="minimum" value="0"/>
+        <property name="maximum" value="0"/>
+        <property name="message" value="Javadoc has illegal ''author'' tag."/>
+        <property name="fileExtensions" value="java"/>
+    </module>
+
+    <!-- Checks that property files contain the same keys.         -->
+    <!-- See http://checkstyle.sf.net/config_misc.html#Translation -->
+    <module name="Translation"/>
+
+    <module name="FileLength"/>
+
+    <module name="SuppressWarningsFilter"/>
+    <module name="TreeWalker">
+        <module name="SuppressionCommentFilter">
+            <property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\|]+)"/>
+            <property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\|]+)"/>
+            <property name="checkFormat" value="$1"/>
+        </module>
+        <module name="SuppressWarningsHolder"/>
+
+        <!-- Checks for Javadoc comments.                     -->
+        <!-- See http://checkstyle.sf.net/config_javadoc.html -->
+        <module name="JavadocMethod">
+            <property name="accessModifiers" value="protected"/>
+            <property name="allowMissingReturnTag" value="true"/>
+            <property name="allowMissingParamTags" value="true"/>
+        </module>
+        <module name="JavadocType">
+            <property name="scope" value="protected"/>
+        </module>
+        <module name="JavadocVariable">
+            <property name="scope" value="protected"/>
+        </module>
+        <module name="JavadocStyle"/>
+
+        <!-- Checks for Naming Conventions.                  -->
+        <!-- See http://checkstyle.sf.net/config_naming.html -->
+        <module name="ConstantName"/>
+        <module name="LocalFinalVariableName"/>
+        <module name="LocalVariableName"/>
+        <module name="MemberName"/>
+        <module name="MethodName"/>
+        <module name="PackageName"/>
+        <module name="ParameterName"/>
+        <module name="StaticVariableName"/>
+        <module name="TypeName"/>
+
+        <!-- Checks for imports                              -->
+        <!-- See http://checkstyle.sf.net/config_import.html -->
+        <module name="AvoidStarImport"/>
+        <module name="UnusedImports"/>
+        <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
+        <module name="RedundantImport"/>
+        <module name="ImportOrder">
+            <property name="groups" value="java, javax, jakarta, org.eclipse.parsson"/>
+            <property name="ordered" value="true"/>
+            <property name="separated" value="true"/>
+            <property name="option" value="bottom"/>
+        </module>
+
+        <!-- Checks for blocks. You know, those {}'s         -->
+        <!-- See http://checkstyle.sf.net/config_blocks.html -->
+        <module name="AvoidNestedBlocks"/>
+        <module name="EmptyBlock">
+            <property name="option" value="TEXT"/>
+            <property name="tokens" value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
+        </module>
+        <module name="NeedBraces">
+            <property name="allowSingleLineStatement" value="true"/>
+        </module>
+        <module name="LeftCurly"/>
+        <module name="RightCurly"/>
+        <module name="RightCurly">
+            <property name="option" value="alone"/>
+            <property name="tokens"
+                    value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT, INSTANCE_INIT"/>
+        </module>
+
+        <!-- Indentation -->
+        <property name="tabWidth" value="4"/>
+
+        <!-- Wrapping Lines -->
+        <module name="NoLineWrap"/>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="DOT"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="COMMA"/>
+            <property name="option" value="EOL"/>
+        </module>
+
+        <!-- Several variable declaration on one line: int i, p; -->
+        <module name="MultipleVariableDeclarations"/>
+
+        <module name="OuterTypeFilename"/>
+        <module name="OneTopLevelClass"/>
+
+        <!-- Checks for whitespace                               -->
+        <!-- See http://checkstyle.sf.net/config_whitespace.html -->
+        <module name="OperatorWrap"/>
+        <module name="WhitespaceAfter"/>
+        <module name="MethodParamPad"/>
+        <module name="NoWhitespaceAfter"/>
+        <module name="NoWhitespaceBefore"/>
+        <module name="ParenPad"/>
+        <module name="TypecastParenPad"/>
+        <module name="WhitespaceAfter"/>
+        <module name="WhitespaceAround">
+            <!-- Removed static initializer issues: RCURLY, SLIST -->
+            <property name="tokens"
+                    value="ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV,
+                            DIV_ASSIGN, DO_WHILE, EQUAL, GE, GT, LAND, LCURLY, LE, LITERAL_ASSERT, LITERAL_CATCH, LITERAL_DO,
+                            LITERAL_ELSE, LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN, LITERAL_SWITCH,
+                            LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS, MINUS_ASSIGN, MOD, MOD_ASSIGN,
+                            NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION, SL, SL_ASSIGN, SR, SR_ASSIGN, STAR, STAR_ASSIGN,
+                            TYPE_EXTENSION_AND"/>
+            <property name="allowEmptyConstructors" value="true"/>
+            <property name="allowEmptyMethods" value="true"/>
+            <property name="allowEmptyTypes" value="true"/>
+            <property name="allowEmptyLoops" value="true"/>
+            <message key="ws.notFollowed"
+                    value="WhitespaceAround: ''{0}'' is not followed by whitespace. Empty blocks may only be represented as '{}' when not part of a multi-block statement (4.1.3)"/>
+            <message key="ws.notPreceded"
+                    value="WhitespaceAround: ''{0}'' is not preceded with whitespace."/>
+        </module>
+
+        <module name="GenericWhitespace">
+            <message key="ws.followed"
+                    value="GenericWhitespace ''{0}'' is followed by whitespace."/>
+            <message key="ws.preceded"
+                    value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
+            <message key="ws.illegalFollow"
+                    value="GenericWhitespace ''{0}'' should followed by whitespace."/>
+            <message key="ws.notPreceded"
+                    value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
+        </module>
+
+        <!-- Modifier Checks                                    -->
+        <!-- See http://checkstyle.sf.net/config_modifiers.html -->
+        <module name="ModifierOrder"/>
+        <module name="RedundantModifier"/>
+
+        <!-- Checks for common coding problems               -->
+        <!-- See http://checkstyle.sf.net/config_coding.html -->
+        <module name="EmptyStatement"/>
+        <module name="EqualsHashCode"/>
+        <module name="IllegalInstantiation"/>
+        <module name="InnerAssignment"/>
+        <module name="MissingSwitchDefault"/>
+
+        <module name="SimplifyBooleanExpression"/>
+        <module name="SimplifyBooleanReturn"/>
+
+        <!-- Checks for class design                         -->
+        <!-- See http://checkstyle.sf.net/config_design.html -->
+        <module name="HideUtilityClassConstructor"/>
+        <module name="InterfaceIsType"/>
+        <module name="VisibilityModifier">
+            <property name="packageAllowed" value="true"/>
+        </module>
+        <module name="ThrowsCount">
+            <property name="max" value="3"/>
+        </module>
+
+        <!-- Miscellaneous other checks.                   -->
+        <!-- See http://checkstyle.sf.net/config_misc.html -->
+        <module name="ArrayTypeStyle"/>
+        <module name="TodoComment"/>
+        <module name="UpperEll"/>
+
+        <module name="OneStatementPerLine"/>
+<!--        <module name="FallThrough"/>-->
+
+        <module name="NoFinalizer"/>
+    </module>
+</module>
diff --git a/pom.xml b/pom.xml
index cac37a4e..ff2d697c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -275,6 +275,19 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>run-checkstyle</id>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                        <phase>validate</phase>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
 
         <pluginManagement>
@@ -380,6 +393,31 @@
                     <artifactId>maven-gpg-plugin</artifactId>
                     <version>3.1.0</version>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-checkstyle-plugin</artifactId>
+                    <version>3.3.1</version>
+                    <configuration>
+                        <configLocation>etc/config/checkstyle.xml</configLocation>
+                        <suppressionsLocation>etc/config/checkstyle-suppressions.xml</suppressionsLocation>
+                        <consoleOutput>true</consoleOutput>
+                        <failsOnError>true</failsOnError>
+                        <linkXRef>false</linkXRef>
+                    </configuration>
+                    <dependencies>
+                        <dependency>
+                            <groupId>com.puppycrawl.tools</groupId>
+                            <artifactId>checkstyle</artifactId>
+                            <version>10.12.4</version>
+                            <exclusions>
+                                <exclusion>
+                                    <groupId>com.sun</groupId>
+                                    <artifactId>tools</artifactId>
+                                </exclusion>
+                            </exclusions>
+                        </dependency>
+                    </dependencies>
+                </plugin>
             </plugins>
         </pluginManagement>
     </build>