gradle Getting started with gradle More about tasks

Example

First of all: operator << (leftShift) is equivalent of doLast {closure}. From gradle 3.2 it is deprecated. All the task code are writing in a build.gradle.

A task represents some atomic piece of work which a build performs. This might be compiling some classes, creating a JAR, generating Javadoc, or publishing some archives to a repository.

Gradle supports two big types of tasks: simple and enhanced.

Let's observe some task definition styles:

task hello {
    doLast{
       //some code
    }    
}

Or the:

task(hello) {
    doLast{
       //some code
    }    
}

This tasks above are equivalents. Also, you can provide some extensions to the task, such as: dependsOn,mustRunAfter, type etc. You can extend task by adding actions after task definition, like this:

task hello {
    doLast{
       println 'Inside task'
    }    
}
hello.doLast {
    println 'added code'
}

When we'll execute this we got:

> gradle -q hello
    Inside task
    added code

Questions about task dependencies and ordering examined here

Let's talk about two big types of task.

Simple:

Tasks which we define with an action closure:

    task hello {
        doLast{
        println "Hello from a simple task"
        }
    }

Enhanced

Enhanced it is a task with a preconfigured behavior. All plugins that you using in your project are the extended, or the enhanced tasks. Let's create ours and you will understand how it works:

task hello(type: HelloTask)

class HelloTask extends DefaultTask {
    @TaskAction
    def greet() {
        println 'hello from our custom task'
    }
}

Also, we can pass parameters to our task, like this:

class HelloTask extends DefaultTask {
    String greeting = "This is default greeting"
    @TaskAction
    def greet() {
        println greeting
    }
}

And from now on we can rewrite our task like so:

   //this is our old task definition style
task oldHello(type: HelloTask) 
   //this is our new task definition style     
task newHello(type: HelloTask) {
    greeting = 'This is not default greeting!'
}

When we'll execute this we got:

> gradle -q oldHello
This is default greeting

> gradle -q newHello
This is not default greeting!

All questions about development gradle plugins onto official site