griffin-doc/dev/code-style.md - griffin - Git at Google

 <!--
 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.
 -->

 # Apache Griffin Development Code Style Config Guide
 Apache Griffin consists of three main modules - Measure, Services and UI. These are developed using Scala, Java and Angular 2 respectively.

 Quoting the Databricks-Apache Spark Code Style Guide at [link](https://github.com/databricks/scala-style-guide) :
 > Code is written once by its author, but read and modified multiple times by lots of other engineers. As most bugs actually come from future modification of the code, we need to optimize our codebase for long-term, global readability and maintainability. The best way to achieve this is to write simple code.

 So it's necessary to define a bunch of code style rules, which are to be followed by all contributors and committers so as ot keep the code base consistent.


 ## Config Java Code Style
 We suggest developers use automatic tools to check code violation like [CheckStyle](https://github.com/checkstyle/checkstyle).<br>
 + Firstly, you need to apply Apache Griffin's Java Code Style Rules. Copy configuration and save as griffin_check.xml
 ```xml
 <?xml version="1.0"?>
 <!DOCTYPE module PUBLIC
         "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
         "https://checkstyle.org/dtds/configuration_1_3.dtd">

 <!--
     Checkstyle configuration that checks the Griffin coding conventions extending Google Java Style
     that can be found at https://google.github.io/styleguide/javaguide.html.

     Checkstyle is very configurable. Be sure to read the documentation at
     http://checkstyle.sf.net (or in your downloaded distribution).

     To completely disable a check, just comment it out or delete it from the file.

     Authors: Max Vetrenko, Ruslan Diachenko, Roman Ivanov.
  -->

 <module name = "Checker">
     <property name="charset" value="UTF-8"/>

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

     <property name="fileExtensions" value="java, properties, xml"/>
     <!-- Checks for whitespace                               -->
     <!-- See http://checkstyle.sf.net/config_whitespace.html -->
     <module name="FileTabCharacter">
         <property name="eachLine" value="true"/>
     </module>

     <module name="TreeWalker">
         <module name="OuterTypeFilename"/>
         <module name="IllegalTokenText">
             <property name="tokens" value="STRING_LITERAL, CHAR_LITERAL"/>
             <property name="format"
                       value="\\u00(09|0(a|A)|0(c|C)|0(d|D)|22|27|5(C|c))|\\(0(10|11|12|14|15|42|47)|134)"/>
             <property name="message"
                       value="Consider using special escape sequence instead of octal value or Unicode escaped value."/>
         </module>
         <module name="AvoidEscapedUnicodeCharacters">
             <property name="allowEscapesForControlCharacters" value="true"/>
             <property name="allowByTailComment" value="true"/>
             <property name="allowNonPrintableEscapes" value="true"/>
         </module>
         <module name="LineLength">
             <property name="max" value="100"/>
             <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
         </module>
         <module name="AvoidStarImport"/>
         <module name="OneTopLevelClass"/>
         <module name="NoLineWrap"/>
         <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"/>
         <module name="LeftCurly"/>
         <module name="RightCurly">
             <property name="id" value="RightCurlySame"/>
             <property name="tokens"
                       value="LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE,
                     LITERAL_DO"/>
         </module>
         <module name="RightCurly">
             <property name="id" value="RightCurlyAlone"/>
             <property name="option" value="alone"/>
             <property name="tokens"
                       value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT,
                     INSTANCE_INIT"/>
         </module>
         <module name="WhitespaceAround">
             <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="OneStatementPerLine"/>
         <module name="MultipleVariableDeclarations"/>
         <module name="ArrayTypeStyle"/>
         <module name="MissingSwitchDefault"/>
         <module name="FallThrough"/>
         <module name="UpperEll"/>
         <module name="ModifierOrder"/>
         <module name="EmptyLineSeparator">
             <property name="allowNoEmptyLineBetweenFields" value="true"/>
         </module>
         <module name="SeparatorWrap">
             <property name="id" value="SeparatorWrapDot"/>
             <property name="tokens" value="DOT"/>
             <property name="option" value="nl"/>
         </module>
         <module name="SeparatorWrap">
             <property name="id" value="SeparatorWrapComma"/>
             <property name="tokens" value="COMMA"/>
             <property name="option" value="EOL"/>
         </module>
         <module name="SeparatorWrap">
             <!-- ELLIPSIS is EOL until https://github.com/google/styleguide/issues/258 -->
             <property name="id" value="SeparatorWrapEllipsis"/>
             <property name="tokens" value="ELLIPSIS"/>
             <property name="option" value="EOL"/>
         </module>
         <module name="SeparatorWrap">
             <!-- ARRAY_DECLARATOR is EOL until https://github.com/google/styleguide/issues/259 -->
             <property name="id" value="SeparatorWrapArrayDeclarator"/>
             <property name="tokens" value="ARRAY_DECLARATOR"/>
             <property name="option" value="EOL"/>
         </module>
         <module name="SeparatorWrap">
             <property name="id" value="SeparatorWrapMethodRef"/>
             <property name="tokens" value="METHOD_REF"/>
             <property name="option" value="nl"/>
         </module>
         <module name="PackageName">
             <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
             <message key="name.invalidPattern"
                      value="Package name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="TypeName">
             <message key="name.invalidPattern"
                      value="Type name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="LambdaParameterName">
             <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
             <message key="name.invalidPattern"
                      value="Lambda parameter name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="CatchParameterName">
             <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
             <message key="name.invalidPattern"
                      value="Catch parameter name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="ClassTypeParameterName">
             <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
             <message key="name.invalidPattern"
                      value="Class type name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="MethodTypeParameterName">
             <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
             <message key="name.invalidPattern"
                      value="Method type name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="InterfaceTypeParameterName">
             <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
             <message key="name.invalidPattern"
                      value="Interface type name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="NoFinalizer"/>
         <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>
         <module name="Indentation">
             <property name="basicOffset" value="4"/>
             <property name="braceAdjustment" value="0"/>
             <property name="caseIndent" value="4"/>
             <property name="throwsIndent" value="4"/>
             <property name="lineWrappingIndentation" value="4"/>
             <property name="arrayInitIndent" value="2"/>
         </module>
         <module name="AbbreviationAsWordInName">
             <property name="ignoreFinal" value="false"/>
             <property name="allowedAbbreviationLength" value="1"/>
         </module>
         <module name="OverloadMethodsDeclarationOrder"/>
         <module name="VariableDeclarationUsageDistance"/>
         <module name="CustomImportOrder">
             <property name="sortImportsInGroupAlphabetically" value="true"/>
             <property name="separateLineBetweenGroups" value="true"/>
             <property name="customImportOrderRules" value="STATIC###THIRD_PARTY_PACKAGE"/>
         </module>
         <module name="MethodParamPad"/>
         <module name="NoWhitespaceBefore">
             <property name="tokens"
                       value="COMMA, SEMI, POST_INC, POST_DEC, DOT, ELLIPSIS, METHOD_REF"/>
             <property name="allowLineBreaks" value="true"/>
         </module>
         <module name="ParenPad"/>
         <module name="OperatorWrap">
             <property name="option" value="NL"/>
             <property name="tokens"
                       value="BAND, BOR, BSR, BXOR, DIV, EQUAL, GE, GT, LAND, LE, LITERAL_INSTANCEOF, LOR,
                     LT, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR, METHOD_REF "/>
         </module>
         <module name="AnnotationLocation">
             <property name="id" value="AnnotationLocationMostCases"/>
             <property name="tokens"
                       value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF"/>
         </module>
         <module name="AnnotationLocation">
             <property name="id" value="AnnotationLocationVariables"/>
             <property name="tokens" value="VARIABLE_DEF"/>
             <property name="allowSamelineMultipleAnnotations" value="true"/>
         </module>
         <module name="NonEmptyAtclauseDescription"/>
         <module name="JavadocTagContinuationIndentation"/>
         <module name="SummaryJavadoc">
             <property name="forbiddenSummaryFragments"
                       value="^@return the *|^This method returns |^A [{]@code [a-zA-Z0-9]+[}]( is a )"/>
         </module>
         <module name="JavadocParagraph"/>
         <module name="AtclauseOrder">
             <property name="tagOrder" value="@param, @return, @throws, @deprecated"/>
             <property name="target"
                       value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
         </module>
         <module name="JavadocMethod">
             <property name="scope" value="public"/>
             <property name="allowMissingParamTags" value="true"/>
             <property name="allowMissingThrowsTags" value="true"/>
             <property name="allowMissingReturnTag" value="true"/>
             <property name="minLineCount" value="2"/>
             <property name="allowedAnnotations" value="Override, Test"/>
             <property name="allowThrowsTagsForSubclasses" value="true"/>
         </module>
         <module name="MethodName">
             <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9_]*$"/>
             <message key="name.invalidPattern"
                      value="Method name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="SingleLineJavadoc">
             <property name="ignoreInlineTags" value="false"/>
         </module>
         <module name="EmptyCatchBlock">
             <property name="exceptionVariableName" value="expected"/>
         </module>
         <module name="CommentsIndentation"/>
     </module>
 </module>
 ```
 + Secondly, you should enable rule check during code building
     + Enable In Maven
     ```xml
     <plugin>
     	<groupId>org.apache.maven.plugins</groupId>
     	<artifactId>maven-checkstyle-plugin</artifactId>
     	<version>3.0.0</version>
     	<dependencies>
     		<dependency>
     			<groupId>com.puppycrawl.tools</groupId>
     			<artifactId>checkstyle</artifactId>
     			<version>8.11</version>
     		</dependency>
     	</dependencies>
     	<executions>
     		<execution>
     			<id>verify-style</id>
     			<phase>process-classes</phase>
     			<goals>
     				<goal>check</goal>
     			</goals>
     		</execution>
     	</executions>
     	<configuration>
     		<configLocation>griffin_check.xml</configLocation>
     		<enableFilesSummary>false</enableFilesSummary>
     	</configuration>
     </plugin>
     ```
     + Enable In IntelliJ IDE
         + Download CheckStyle-IDEA Plugin

         ![idea plugin](../img/devguide/style-check-plugin-idea.png)

         + Add Apache Griffin Checks In IDEA Setting

         ![idea setting](../img/devguide/config-addition-idea.png)

         + Check Codes Convention

         ![idea check-run](../img/devguide/check-run-idea.png)


 ## Scala Code Style Guide

 Since only Measure module is written in Scala, this guide applies to only the measure module.
 For Scala code, Apache Griffin follows the official [Scala style guide](https://docs.scala-lang.org/style/)
 and [Apache Spark Scala guide](https://github.com/databricks/scala-style-guide).

 #### Guide Update History
 | Version | Date       | Changes |
 |:-------:|:-----------|:--------|
 | 1       | 2019-12-24 | Initial version: Added Scala Code Style Guide |

 #### Configuration
 For code style checks Apache Griffin uses [Scalastyle](http://www.scalastyle.org/) and formatting is handled
 by [Scalafmt](https://scalameta.org/scalafmt/).

 Configurations for both Scalastyle and Scalafmt are present in the root of Apache Griffin repository.
  - Scalastyle Config: `scalastyle-config.xml`
  - Scalafmt Config: `.scalafmt.conf`

 ####  Formatting and Style Check

 Although automatic formatting and checks are built into the build steps of Apache Griffin,
 to manually format Scala code and check for possible style violations, run the following commands.

 ```
 ## assuming current working directory is griffin root

 cd measure
 mvn clean verify -DskipTests
 ```

 ####  IntelliJ IDEA Setup

 Navigate to _Settings > Editor > Code Style > Scala_ and follow the screenshots below to ensure coding standards
  in the IntelliJ IDEA.
 ![scala_code_style_1](../img/devguide/scala-intellij-idea/1.png)
 ![scala_code_style_2](../img/devguide/scala-intellij-idea/2.png)
 ![scala_code_style_3](../img/devguide/scala-intellij-idea/3.png)
 ![scala_code_style_4](../img/devguide/scala-intellij-idea/4.png)
 ![scala_code_style_5](../img/devguide/scala-intellij-idea/5.png)
 ![scala_code_style_6](../img/devguide/scala-intellij-idea/6.png)


 #### Important Notes
 1. [Guide Update History](#guide-update-history) section must be updated each time any section of
 Scala Code Style Guide is edited.
 2. Formatting and code style checks must be ensured each time before submitting or updating a pull request as
 violations will cause build failures.
 3. If you’re not sure about the right style for something, try to follow the style of the existing codebase.
 Look at whether there are other examples in the code that use your feature.

 In case of any queries or dilemmas feel free to reach out to the other contributors and committers
 on the [dev@griffin.apache.org](mailto:dev@griffin.apache.org) list.

 ## Config Angular 2 Code Style
 to do
	<!--
	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.
	-->

	# Apache Griffin Development Code Style Config Guide
	Apache Griffin consists of three main modules - Measure, Services and UI. These are developed using Scala, Java and Angular 2 respectively.

	Quoting the Databricks-Apache Spark Code Style Guide at [link](https://github.com/databricks/scala-style-guide) :
	> Code is written once by its author, but read and modified multiple times by lots of other engineers. As most bugs actually come from future modification of the code, we need to optimize our codebase for long-term, global readability and maintainability. The best way to achieve this is to write simple code.

	So it's necessary to define a bunch of code style rules, which are to be followed by all contributors and committers so as ot keep the code base consistent.


	## Config Java Code Style
	We suggest developers use automatic tools to check code violation like [CheckStyle](https://github.com/checkstyle/checkstyle).<br>
	+ Firstly, you need to apply Apache Griffin's Java Code Style Rules. Copy configuration and save as griffin_check.xml
	```xml
	<?xml version="1.0"?>
	<!DOCTYPE module PUBLIC
	"-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
	"https://checkstyle.org/dtds/configuration_1_3.dtd">

	<!--
	Checkstyle configuration that checks the Griffin coding conventions extending Google Java Style
	that can be found at https://google.github.io/styleguide/javaguide.html.

	Checkstyle is very configurable. Be sure to read the documentation at
	http://checkstyle.sf.net (or in your downloaded distribution).

	To completely disable a check, just comment it out or delete it from the file.

	Authors: Max Vetrenko, Ruslan Diachenko, Roman Ivanov.
	-->

	<module name = "Checker">
	<property name="charset" value="UTF-8"/>

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

	<property name="fileExtensions" value="java, properties, xml"/>
	<!-- Checks for whitespace -->
	<!-- See http://checkstyle.sf.net/config_whitespace.html -->
	<module name="FileTabCharacter">
	<property name="eachLine" value="true"/>
	</module>

	<module name="TreeWalker">
	<module name="OuterTypeFilename"/>
	<module name="IllegalTokenText">
	<property name="tokens" value="STRING_LITERAL, CHAR_LITERAL"/>
	<property name="format"
	value="\\u00(09\|0(a\|A)\|0(c\|C)\|0(d\|D)\|22\|27\|5(C\|c))\|\\(0(10\|11\|12\|14\|15\|42\|47)\|134)"/>
	<property name="message"
	value="Consider using special escape sequence instead of octal value or Unicode escaped value."/>
	</module>
	<module name="AvoidEscapedUnicodeCharacters">
	<property name="allowEscapesForControlCharacters" value="true"/>
	<property name="allowByTailComment" value="true"/>
	<property name="allowNonPrintableEscapes" value="true"/>
	</module>
	<module name="LineLength">
	<property name="max" value="100"/>
	<property name="ignorePattern" value="^package.\|^import.\|a href\|href\|http://\|https://\|ftp://"/>
	</module>
	<module name="AvoidStarImport"/>
	<module name="OneTopLevelClass"/>
	<module name="NoLineWrap"/>
	<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"/>
	<module name="LeftCurly"/>
	<module name="RightCurly">
	<property name="id" value="RightCurlySame"/>
	<property name="tokens"
	value="LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE,
	LITERAL_DO"/>
	</module>
	<module name="RightCurly">
	<property name="id" value="RightCurlyAlone"/>
	<property name="option" value="alone"/>
	<property name="tokens"
	value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT,
	INSTANCE_INIT"/>
	</module>
	<module name="WhitespaceAround">
	<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="OneStatementPerLine"/>
	<module name="MultipleVariableDeclarations"/>
	<module name="ArrayTypeStyle"/>
	<module name="MissingSwitchDefault"/>
	<module name="FallThrough"/>
	<module name="UpperEll"/>
	<module name="ModifierOrder"/>
	<module name="EmptyLineSeparator">
	<property name="allowNoEmptyLineBetweenFields" value="true"/>
	</module>
	<module name="SeparatorWrap">
	<property name="id" value="SeparatorWrapDot"/>
	<property name="tokens" value="DOT"/>
	<property name="option" value="nl"/>
	</module>
	<module name="SeparatorWrap">
	<property name="id" value="SeparatorWrapComma"/>
	<property name="tokens" value="COMMA"/>
	<property name="option" value="EOL"/>
	</module>
	<module name="SeparatorWrap">
	<!-- ELLIPSIS is EOL until https://github.com/google/styleguide/issues/258 -->
	<property name="id" value="SeparatorWrapEllipsis"/>
	<property name="tokens" value="ELLIPSIS"/>
	<property name="option" value="EOL"/>
	</module>
	<module name="SeparatorWrap">
	<!-- ARRAY_DECLARATOR is EOL until https://github.com/google/styleguide/issues/259 -->
	<property name="id" value="SeparatorWrapArrayDeclarator"/>
	<property name="tokens" value="ARRAY_DECLARATOR"/>
	<property name="option" value="EOL"/>
	</module>
	<module name="SeparatorWrap">
	<property name="id" value="SeparatorWrapMethodRef"/>
	<property name="tokens" value="METHOD_REF"/>
	<property name="option" value="nl"/>
	</module>
	<module name="PackageName">
	<property name="format" value="^[a-z]+(\.[a-z][a-z0-9])$"/>
	<message key="name.invalidPattern"
	value="Package name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="TypeName">
	<message key="name.invalidPattern"
	value="Type name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="LambdaParameterName">
	<property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
	<message key="name.invalidPattern"
	value="Lambda parameter name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="CatchParameterName">
	<property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
	<message key="name.invalidPattern"
	value="Catch parameter name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="ClassTypeParameterName">
	<property name="format" value="(^[A-Z][0-9]?)$\|([A-Z][a-zA-Z0-9]*[T]$)"/>
	<message key="name.invalidPattern"
	value="Class type name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="MethodTypeParameterName">
	<property name="format" value="(^[A-Z][0-9]?)$\|([A-Z][a-zA-Z0-9]*[T]$)"/>
	<message key="name.invalidPattern"
	value="Method type name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="InterfaceTypeParameterName">
	<property name="format" value="(^[A-Z][0-9]?)$\|([A-Z][a-zA-Z0-9]*[T]$)"/>
	<message key="name.invalidPattern"
	value="Interface type name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="NoFinalizer"/>
	<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>
	<module name="Indentation">
	<property name="basicOffset" value="4"/>
	<property name="braceAdjustment" value="0"/>
	<property name="caseIndent" value="4"/>
	<property name="throwsIndent" value="4"/>
	<property name="lineWrappingIndentation" value="4"/>
	<property name="arrayInitIndent" value="2"/>
	</module>
	<module name="AbbreviationAsWordInName">
	<property name="ignoreFinal" value="false"/>
	<property name="allowedAbbreviationLength" value="1"/>
	</module>
	<module name="OverloadMethodsDeclarationOrder"/>
	<module name="VariableDeclarationUsageDistance"/>
	<module name="CustomImportOrder">
	<property name="sortImportsInGroupAlphabetically" value="true"/>
	<property name="separateLineBetweenGroups" value="true"/>
	<property name="customImportOrderRules" value="STATIC###THIRD_PARTY_PACKAGE"/>
	</module>
	<module name="MethodParamPad"/>
	<module name="NoWhitespaceBefore">
	<property name="tokens"
	value="COMMA, SEMI, POST_INC, POST_DEC, DOT, ELLIPSIS, METHOD_REF"/>
	<property name="allowLineBreaks" value="true"/>
	</module>
	<module name="ParenPad"/>
	<module name="OperatorWrap">
	<property name="option" value="NL"/>
	<property name="tokens"
	value="BAND, BOR, BSR, BXOR, DIV, EQUAL, GE, GT, LAND, LE, LITERAL_INSTANCEOF, LOR,
	LT, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR, METHOD_REF "/>
	</module>
	<module name="AnnotationLocation">
	<property name="id" value="AnnotationLocationMostCases"/>
	<property name="tokens"
	value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF"/>
	</module>
	<module name="AnnotationLocation">
	<property name="id" value="AnnotationLocationVariables"/>
	<property name="tokens" value="VARIABLE_DEF"/>
	<property name="allowSamelineMultipleAnnotations" value="true"/>
	</module>
	<module name="NonEmptyAtclauseDescription"/>
	<module name="JavadocTagContinuationIndentation"/>
	<module name="SummaryJavadoc">
	<property name="forbiddenSummaryFragments"
	value="^@return the *\|^This method returns \|^A [{]@code [a-zA-Z0-9]+[}]( is a )"/>
	</module>
	<module name="JavadocParagraph"/>
	<module name="AtclauseOrder">
	<property name="tagOrder" value="@param, @return, @throws, @deprecated"/>
	<property name="target"
	value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
	</module>
	<module name="JavadocMethod">
	<property name="scope" value="public"/>
	<property name="allowMissingParamTags" value="true"/>
	<property name="allowMissingThrowsTags" value="true"/>
	<property name="allowMissingReturnTag" value="true"/>
	<property name="minLineCount" value="2"/>
	<property name="allowedAnnotations" value="Override, Test"/>
	<property name="allowThrowsTagsForSubclasses" value="true"/>
	</module>
	<module name="MethodName">
	<property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9_]*$"/>
	<message key="name.invalidPattern"
	value="Method name ''{0}'' must match pattern ''{1}''."/>
	</module>
	<module name="SingleLineJavadoc">
	<property name="ignoreInlineTags" value="false"/>
	</module>
	<module name="EmptyCatchBlock">
	<property name="exceptionVariableName" value="expected"/>
	</module>
	<module name="CommentsIndentation"/>
	</module>
	</module>
	```
	+ Secondly, you should enable rule check during code building
	+ Enable In Maven
	```xml
	<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-checkstyle-plugin</artifactId>
	<version>3.0.0</version>
	<dependencies>
	<dependency>
	<groupId>com.puppycrawl.tools</groupId>
	<artifactId>checkstyle</artifactId>
	<version>8.11</version>
	</dependency>
	</dependencies>
	<executions>
	<execution>
	<id>verify-style</id>
	<phase>process-classes</phase>
	<goals>
	<goal>check</goal>
	</goals>
	</execution>
	</executions>
	<configuration>
	<configLocation>griffin_check.xml</configLocation>
	<enableFilesSummary>false</enableFilesSummary>
	</configuration>
	</plugin>
	```
	+ Enable In IntelliJ IDE
	+ Download CheckStyle-IDEA Plugin

	![idea plugin](../img/devguide/style-check-plugin-idea.png)

	+ Add Apache Griffin Checks In IDEA Setting

	![idea setting](../img/devguide/config-addition-idea.png)

	+ Check Codes Convention

	![idea check-run](../img/devguide/check-run-idea.png)


	## Scala Code Style Guide

	Since only Measure module is written in Scala, this guide applies to only the measure module.
	For Scala code, Apache Griffin follows the official [Scala style guide](https://docs.scala-lang.org/style/)
	and [Apache Spark Scala guide](https://github.com/databricks/scala-style-guide).

	#### Guide Update History
	\| Version \| Date \| Changes \|
	\|:-------:\|:-----------\|:--------\|
	\| 1 \| 2019-12-24 \| Initial version: Added Scala Code Style Guide \|

	#### Configuration
	For code style checks Apache Griffin uses [Scalastyle](http://www.scalastyle.org/) and formatting is handled
	by [Scalafmt](https://scalameta.org/scalafmt/).

	Configurations for both Scalastyle and Scalafmt are present in the root of Apache Griffin repository.
	- Scalastyle Config: `scalastyle-config.xml`
	- Scalafmt Config: `.scalafmt.conf`

	#### Formatting and Style Check

	Although automatic formatting and checks are built into the build steps of Apache Griffin,
	to manually format Scala code and check for possible style violations, run the following commands.

	```
	## assuming current working directory is griffin root

	cd measure
	mvn clean verify -DskipTests
	```

	#### IntelliJ IDEA Setup

	Navigate to _Settings > Editor > Code Style > Scala_ and follow the screenshots below to ensure coding standards
	in the IntelliJ IDEA.
	![scala_code_style_1](../img/devguide/scala-intellij-idea/1.png)
	![scala_code_style_2](../img/devguide/scala-intellij-idea/2.png)
	![scala_code_style_3](../img/devguide/scala-intellij-idea/3.png)
	![scala_code_style_4](../img/devguide/scala-intellij-idea/4.png)
	![scala_code_style_5](../img/devguide/scala-intellij-idea/5.png)
	![scala_code_style_6](../img/devguide/scala-intellij-idea/6.png)


	#### Important Notes
	1. [Guide Update History](#guide-update-history) section must be updated each time any section of
	Scala Code Style Guide is edited.
	2. Formatting and code style checks must be ensured each time before submitting or updating a pull request as
	violations will cause build failures.
	3. If you’re not sure about the right style for something, try to follow the style of the existing codebase.
	Look at whether there are other examples in the code that use your feature.

	In case of any queries or dilemmas feel free to reach out to the other contributors and committers
	on the [dev@griffin.apache.org](mailto:dev@griffin.apache.org) list.

	## Config Angular 2 Code Style
	to do