Gradle

Build automation tool for multi-language software development. It controls the development process in the tasks of compilation and packaging to testing, deployment and publishing. Supports Java, C/C++ and JavaScript.

Grade has a declarative language, which express intent, being a very maintanable approach.

Comparing Gradle to Ant and Maven

Ant provides XML Build Script, which specify everything that we need.
Maven has more conventions than Ant and it is extensible. Also written in XML and harder to maintain.

Installing Gradle

https://gradle.org

Gradle Builds

Gradle has a build file, typically build.gradle
The file contains taks, plugins and dependencies.

Task Example

task hello {
    doLast {
        println "Hello, Gradle"
    }
}

Running a Task

gradle hello

Tasks

Gradle tasks are code that Gradle executes. The language used to write Gradle tasks is Groovy. A task will have a lifecycle, properties, actions and dependencies.

Example

task MyTask {
    description "This is an example of task"
    doLast {
        println "Executing Last in MyTask"
    }
    doFirst {
        println "Executing First in MyTask"
    }
}

To see all tasks we can use

$ gradle tasks --all

Phases

Initialization Phase - Used to configure multi project builds
Configuration phase - Executed code in the task that not the action
Execution phase - Execute the task action

Dependencies

We can make a task depending on another task.

task DependencyTask {
    description "Dependency task"
    doLast {
        println "Dependency task"
    }
}

task MyTask {
    description "This is an example of main task"
    doLast {
        println "Main task"
    }
}

MyTask.dependsOn(DependencyTask)

Properties

We can define specific properties to gradle build file, and use them as variables.

ext.projectName = "Testing Gradle"
def projectVersion = "2.0"

task MyTask {
    description "Project $projectName"
    doLast {
        println "This is an example of task with a property: version $projectVersion"
    }
}

Dependencies

It's possible to specify how we want the dependencies to behave

mustRunAfter - If two tasks execute, one must run after the other
shouldRunAfter - If two taks execvute, one should run after the other. It will ignore circular dependencies.
finalizedBy - Inverted dependency. When a task run, it triggers the tasks that specify finalize by it.

Typed Tasks

For complex and reusable tasks like: copying files, zipping files, etc.

task copyImages (type: Copy) {
    from 'img/src/'
    into 'img/dest/'
}

Copy Task

def contentSpec = copySpec {
    exclude { it.file.name.startsWith('invalid') }
    from 'img/src'
}

task copyImages (type: Copy) {
    with contentSpec
    into 'img/dest/'
}

Replace content

task copyConfig (type: Copy) {
    include 'web.txt'
    from 'files/src'
    into 'files/dest'
    expand (
        [placeholder: 'Replaced the placeholder']
    )
}