Demystifying Gradle Build Scripts

Kunal Dabir

@kdabir

github.com/kdabir

slido.com  #GRADLE

About me

What do we Build?

  • Libraries

  • Web Apps

  • Micro Services

  • Mobile Apps

  • Native (Desktop) Apps

  • CLI Apps

What do we Build?

Artifacts

What do we write?

  • Main Source Code

  • Resources / Assets

  • Configuration

  • Tests

What do we have?

Source sets

What do we depend on?

Other Artifacts, like libraries, often which are not built by us

What do we depend on?

Dependencies

Where do we get dependencies from?

Repositories
(Package Registries)

Repositories are typically remote servers, access controlled for publishing

How Are Libraries Stored in Repositories?

Repository Format

Different Repositories have their own formats like Ivy, Maven, NPM etc.

Which Are Well Known Repositories

  • Maven Central

  • NPM

  • RubyGems

  • Github Package Registry

  • Corporate Nexus /Artifactory

Who downloads dependencies for us?

Apps - Native/CLI : 

brew, apt-get, yum

 

Libraries:

NPM/Yarn, Bundler/Gems, PIP, Maven/Gradle

Who downloads dependencies for us?

Package Managers

What do we do with built Artifact?

  • Deploy it (to servers)

  • Publish it (as library)

  • Publish it (to app stores)

Where do we publish?

Repositories

Internal or Public

What does a Build Tool do?

  • Compiles source code

  • Runs automated tests

  • Manages dependencies

  • Runs application locally

What does a Build Tool do?

  • Runs static analysis of code

  • Checks code coverage

  • Produces reports

  • Runs database migrations

  • Web assets optimizations

What does a Build Tool do?

  • Packages distributable binaries

  • Publishes artifacts

  • Generates (API) Documentation

  • Tags releases in VCS

  • Deploys application to servers

What does a Build Tool do?

  • And many more tasks...

Everyone Reinvented the wheel...

 

 

... in their favorite language

Evolution

Bash Scripts

Make

Ant

Maven

Gradle

 

Why not write build scripts in just any scripting language?

because they don't speak the language of the domain (terms used in build) 

 

Why not use IDE as build tool?

  • How will it work of CI?

  • Honor other teammate's preferences

  • Running from CLI

 

Why not just a task runner? (ant, grunt, make, rake)

because you have to repeat yourself in every project you build

 

Why not Maven?

  • Maven did many good things in its time

    • Introduced Dependency Management

    • Brough Conventions

  • But

    • XML is verbose

    • Customization is cumbersome

  • ...

 

Why not Maven?

Gradle

What makes Gradle better

  • Rich DSL

  • Excellent dependency resolution

  • Out of the box plugins (sensible defaults)

  • Fully configurable / extensible

  • Flexible syntax

  • Performant

  • Flexible Multi Project support

What makes Gradle better

  • Vibrant community & ecosystem

  • Plethora of Plugins

  • Open source

  • backed by a company

  • Good adoption

Imperative v/s Declarative

  • Imperative Mixes 'how' with 'what'

  • provide steps for execution and ordering.

  • Looks easy at start, hard to maintain and update

What makes Gradle better

Gradle embraces domain modelling as a core tenet. Focusing on the domain model as opposed to the execution model (like prior generation build tools such as Apache Ant) has many advantages. A strong domain model communicates the intent (i.e. the what) over the mechanics (i.e. the how). This allows humans to understand builds at a level that is meaningful to them.

https://docs.gradle.org/current/userguide/software_model.html

Domain Model of a Build

Project

Task

Domain Model of a Build

Project object contains collections of Task Objects and many other methods

Domain Model of a Build

Each Task is an Object on which we can call methods to configure it's behaviour

Project API

  • Central API to the Gradle build script

  • Available as ‘project’ reference in the  build script

    • BuildScript is evaluated against the instance of this project object.

  • Available implicitly in the script

    • methods/properties are looked up on this object by default.

  • One project object per build.gradle

Script blocks

Create a task

task hello 

hello.doLast {
    println "I am a task"
}
task hello {
    doLast {
        println "I am a task"
    }
}

Or

Task ordering

task bye {
  doLast {
    println "I am another task"
  }
}

bye.dependsOn(hello)

Plugins

plugins {
    id 'java'
}
plugins {
    id "org.jetbrains.kotlin.jvm" version "1.6.21"
}

Repositories

repositories {
    mavenCentral()
}

Dependencies

dependencies {
    compile 'org.springframework:spring-core:4.0.6.RELEASE'
    testCompile 'junit:junit:4.12'
}

Running

gradle help

Gradle wrapper

gradle wrapper


./gradlew myTask

Hands On Time

Questions?

slido.com  #GRADLE

twitter.com/kdabir

github.com/kdabir

medly.tech

Demystifying Gradle Build Scripts

By Kunal Dabir

Made with Slides.com

Demystifying Gradle Build Scripts

Gradle is an incredibly flexible build tool but a lot of times developers are taken aback by syntax of Gradle Build Scripts. Lot of Kotlin and Java Developers use Gradle without understanding the underpinning basics of gradle builds. This talk will focus on how to understand Gradle Build files and adhere to its best practises. This talk will provide the lenses to identify the syntactic elements of the Gradle DSL.

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