[JAVA] I want to write a nice build.gradle

What I got stuck or couldn't find when I looked up build.gradle

environment

--Gradle6.4 (released 5/6/2020)

At the beginning

For the time being, Gradle documentation may be a good idea to take a look.

Convenient plugin

Name link to documentation

-java Plugin. Java source cannot be compiled without it -checkstyle Plugin. Useful when aligning styles ([To the description section](introduce #checkstyle)) -shadow Plugin. Required to generate Fat-Jar (Uber-Jar) plugin ([Go to description section](Generate fat-jaruber-jar using #shadow plugin)) -ErrorProne Plugin. Static analysis tool. The one who looks for anti-patterns ([To the description section](introduces #errorprone))

Use Wrapper

Something like ./gradlew or ./gradlew.bat. Can be initialized and updated by running the wrapper task With this, it's okay if the version of gradle installed in the developer's environment is different!

Official documentation: The Gradle Wrapper

Specify the encoding

If not specified, the build result may change between Linux and Windows.

For example, when specifying UTF-8, it looks like this

build.gradle

//compile Java task encoding
compileJava.options.encoding = 'UTF-8'
//compileTest Java task encoding
compileTestJava.options.encoding = 'UTF-8'
//javadoc task encoding
javadoc.options.encoding = 'UTF-8'

Dependency declaration

** Do not use compile or testCompile because they are deprecated ** There are various things such as ʻimplementation and testImplementation, but since it is troublesome, the official document [The Java Plugin](https://docs.gradle.org/6.4/userguide/java_plugin.html#sec:java_plugin_and_dependency_management) What is ʻapi? It is written in The Java Library Plugin

A brief explanation compileOnly is a dependency required at compile time. Not included in FatJar etc. (provided scope in Maven) runtimeOnly is a dependency required at runtime. It can be entered in FatJar etc., but it cannot be referenced from within the source code (I think it is, but I do not know because I have never used it) ʻImplementationis a required dependency at compile time and run time. It can be referenced from within the source code as well as in FatJar, but it cannot be referenced from projects that have this as a dependency (recognized asprovided in Maven). Use Java Library Plugin ʻapi to make it visible

Also, those with test at the beginning (for example, testImplementation) are valid only during testing.

Specify the version range

The official documentation is here: Declaring Versions and Ranges

build.gradle

testImplementation 'org.junit.jupiter:junit-jupiter:5.6.+'

If you do, 5.6. Below will use the latest version at that time. The build result may change depending on the build environment due to this effect, so if you want to prevent it, [Fix Dependencies](#Fix Dependencies))

Fix dependencies

The official documentation is here: Locking dependency versions

Introduce ErrorProne

Add to plugins

build.gradle

    id 'net.ltgt.errorprone' version '1.1.1'

Add to dependency

build.gradle

dependencies {
    // ErrorProne
    errorprone 'com.google.errorprone:error_prone_core:2.+'
}

For Java8, insert the Java9 compiler

build.gradle

dependencies {
    errorproneJavac 'com.google.errorprone:javac:9+181-r4173-1'
}

If you want to be able to run in Java 8 environment or Java 9 or higher, this may be good

build.gradle

if (!JavaVersion.current().isJava9Compatible()) {
    dependencies {
        errorproneJavac 'com.google.errorprone:javac:9+181-r4173-1'
    }
}

It seems that javac will be replaced, so it applies to all compile tasks

Introduce CheckStyle

Add to plugins

build.gradle

plugins {
    id 'checkstyle'
}

Tweak config / checkstyle / checkstyle.xml. For example

checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
    <module name="FileTabCharacter"/>
    <module name="TreeWalker">
        <module name="Indentation">
            <property name="lineWrappingIndentation" value="8"/>
        </module>
        <!-- Imports -->
        <module name="UnusedImports"/>
        <module name="RedundantImport"/>
        <module name="ImportOrder">
            <property name="separated" value="true"/>
            <property name="sortStaticImportsAlphabetically" value="true"/>
        </module>
        <!-- Brackets -->
        <module name="LeftCurly"/>
        <module name="RightCurly"/>
        <module name="NeedBraces"/>
    </module>
</module>

Official documentation looks good

If you execute the build task, it will be executed without permission

Unit test with JUnit

Add to dependency

build.gradle

testImplementation 'org.junit.jupiter:junit-jupiter:5.6.+'

It will be nice to set it like this

build.gradle

tasks.test {
    testLogging.showStandardStreams = true // System.Display out or err in the log
    useJUnitPlatform()
    testLogging {
        events('passed', 'skipped', 'failed')
    }
}

JUnit 5 User Guide

Generate Fat Jar (Uber Jar) using shadow plugin

Add as a plugin

build.gradle

plugins {
    id 'com.github.johnrengelman.shadow' version '5.2.0'
}

Execute the shadowjar task and it will be completed under build / libs

You can relocate, minimize, and rename the jar, but it's a hassle, so the official docs https://imperceptiblethoughts.com/shadow/introduction/

Generate a searchable Javadoc

build.gradle

javadoc {
    if(JavaVersion.current().isJava9Compatible()) {
        options.addBooleanOption('html5', true)
    }
}

This makes the javadoc task look good (requires Java 9 or above)