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Mastering Gradle
Mastering Gradle

Mastering Gradle: Master the technique of developing, migrating, and building automation using Gradle

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Mastering Gradle

Chapter 2. Groovy Essentials for Gradle

In this chapter, we will learn some fundamental concepts of the Groovy programming language. This chapter briefly covers Groovy data types, control structures, object oriented concepts, collections, closures, and builders. This is just the tip of the iceberg. As this is not a Groovy book, we won't be able to cover all the topics. This chapter is meant for beginners who are coming from a Java background and have a basic understanding of Object-oriented programming (OOP) concepts. This will help them get started with Groovy. This chapter will also act as a tool box to proceed with Gradle scripting.

Overview

Groovy is a dynamic programming language for the Java Platform. You might be wondering why we specifically mention the Java platform. By the Java platform, it means Groovy code compiles into the bytecode, and bytecodes are executed on JVM similar to any other Java class. Along with the OOP features, it also provides the capability of scripting languages such as Python and Smalltalk, making them available to use in Groovy using a Java-like syntax.

As Groovy runs on JVM, it can be easily integrated with Java and nicely fits into the existing infrastructure. For example, the build and deployment of Groovy code is the same as the build and deployment of Java code, and you can easily mix Groovy and Java together by just adding another JAR file to the library. Groovy is not the only language that runs on JVM. Some of the other languages are Scala, Clojure, JRuby, Jython, and so on. In my opinion, if you have some Java background, Groovy is much easier to learn when compared with other...

Groovy script for Hello World

We have discussed what Groovy is and some of its important features. Let us create a Hello World program and feel the magic with Groovy. Here we are assuming that Groovy is installed on the system, GROOVY_HOME is pointing to the installation directory and <GROOVY_HOME>/bin has been added to the PATH environment variable:

file: GroovyTest.groovy
  println "Hello Groovy"

And that's all. Yes, for a simple Groovy program, you don't need to declare any packaging, any main class, or any semicolons, only a simple println statement would create your first Groovy program.

To execute the program, use the following command:

$ groovy GroovyTest.groovy
  Hello Groovy

The groovy command is used to execute the Groovy script. The beauty of the Groovy script is that it can execute any file, not only files with the .groovy extension. Even you can write the preceding println statement in the Test.text file and use the groovy command to execute the file....

Data types

The first thing you learn about any programming language are the data types; how any programming language stores the data. Similar to the other programming languages, Groovy also offers a different set of data types for numerical, strings, char, and so on. As compared to Java, there are no primitive types present in Groovy. Groovy treats everything as an object, which makes Groovy a pure Object Oriented language. The problem with primitive data types is that developers can't perform any object-level operations, such as calling methods on them. Also, you can't store them as an object in maps and sets (collections that require objects). The following table shows primitive data types and wrapper types with default values:

Data type

Wrapper type

Default values

byte

Byte

0

short

Short

0

int

Integer

0

long

Long

0L

float

Float

0.0f

double

Double

0.0d

char

Character

\u0000

boolean

Boolean

false

String

Not Applicable

null

Groovy gives you the flexibility...

Classes, beans, and methods

This section introduces classes, methods, and beans. Groovy classes are similar to Java classes declared with the class keyword. Usually, a class definition starts with the package name, and then import package statements. One key difference with the Java counterpart is that Groovy imports six packages and two classes by default. So, if you create any class, these packages and classes are automatically available to you:

import java.lang.* // this is the only default import in Java
import java.util.*
import java.io.*
import java.net.*
import groovy.lang.*
import groovy.util.*
import java.math.BigInteger
import java.math.BigDecimal

Classes and methods in Groovy by default have public access, whereas in Java it is set to package-private. We will start with a sample Groovy class:

class Order {
  int orderNo
  Customer orderedByCustomer
  String description

  static main(args) {
    Order order1 = new Order();
    order1.orderNo = 1;
    order1.orderedByCustomer = new...

Control structures

In this section, we will discuss the basic control structures, namely the if…else statement, the switch statement, the for loop, and the while loop.

The if-else condition

The if…else condition in Groovy is similar to Java with one exception, how Groovy evaluates the logical if condition. In the following example, the if condition is evaluated true for both Boolean and int values. In Groovy, non-zero integers, non-null values, nonempty strings, initialized collections, and a valid matcher are evaluated as Boolean true values. This is known as Groovy Truths. Let's take a look at the following code:

def condition1 = true
int condition2 = 0
if(condition1){
  println("Condition 1 satisfied")
  if(condition2){
    println("Condition 2 satisfied")
  }else{
    println("Condition 2 failed")
  }
}else{
  println("Condition 1 failed")
}

Groovy also supports ternary operators (x? y: z), such as Java, which can be used to write...

Overview


Groovy is a dynamic programming language for the Java Platform. You might be wondering why we specifically mention the Java platform. By the Java platform, it means Groovy code compiles into the bytecode, and bytecodes are executed on JVM similar to any other Java class. Along with the OOP features, it also provides the capability of scripting languages such as Python and Smalltalk, making them available to use in Groovy using a Java-like syntax.

As Groovy runs on JVM, it can be easily integrated with Java and nicely fits into the existing infrastructure. For example, the build and deployment of Groovy code is the same as the build and deployment of Java code, and you can easily mix Groovy and Java together by just adding another JAR file to the library. Groovy is not the only language that runs on JVM. Some of the other languages are Scala, Clojure, JRuby, Jython, and so on. In my opinion, if you have some Java background, Groovy is much easier to learn when compared with other...

Groovy script for Hello World


We have discussed what Groovy is and some of its important features. Let us create a Hello World program and feel the magic with Groovy. Here we are assuming that Groovy is installed on the system, GROOVY_HOME is pointing to the installation directory and <GROOVY_HOME>/bin has been added to the PATH environment variable:

file: GroovyTest.groovy
  println "Hello Groovy"

And that's all. Yes, for a simple Groovy program, you don't need to declare any packaging, any main class, or any semicolons, only a simple println statement would create your first Groovy program.

To execute the program, use the following command:

$ groovy GroovyTest.groovy
  Hello Groovy

The groovy command is used to execute the Groovy script. The beauty of the Groovy script is that it can execute any file, not only files with the .groovy extension. Even you can write the preceding println statement in the Test.text file and use the groovy command to execute the file. File extension doesn...

Data types


The first thing you learn about any programming language are the data types; how any programming language stores the data. Similar to the other programming languages, Groovy also offers a different set of data types for numerical, strings, char, and so on. As compared to Java, there are no primitive types present in Groovy. Groovy treats everything as an object, which makes Groovy a pure Object Oriented language. The problem with primitive data types is that developers can't perform any object-level operations, such as calling methods on them. Also, you can't store them as an object in maps and sets (collections that require objects). The following table shows primitive data types and wrapper types with default values:

Data type

Wrapper type

Default values

byte

Byte

0

short

Short

0

int

Integer

0

long

Long

0L

float

Float

0.0f

double

Double

0.0d

char

Character

\u0000

boolean

Boolean

false

String

Not Applicable

null

Groovy gives you the flexibility to...

Classes, beans, and methods


This section introduces classes, methods, and beans. Groovy classes are similar to Java classes declared with the class keyword. Usually, a class definition starts with the package name, and then import package statements. One key difference with the Java counterpart is that Groovy imports six packages and two classes by default. So, if you create any class, these packages and classes are automatically available to you:

import java.lang.* // this is the only default import in Java
import java.util.*
import java.io.*
import java.net.*
import groovy.lang.*
import groovy.util.*
import java.math.BigInteger
import java.math.BigDecimal

Classes and methods in Groovy by default have public access, whereas in Java it is set to package-private. We will start with a sample Groovy class:

class Order {
  int orderNo
  Customer orderedByCustomer
  String description

  static main(args) {
    Order order1 = new Order();
    order1.orderNo = 1;
    order1.orderedByCustomer = new...
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Description

If you are a developer with some experience in build tool and want to become an expert in build tool, then this book is for you. Basic knowledge of Gradle or any other build tool is essential.

Who is this book for?

If you are a developer with some experience in build tool and want to become an expert in build tool, then this book is for you. Basic knowledge of Gradle or any other build tool is essential.

What you will learn

  • Create and develop a build system with Gradle
  • Understand Groovy basics and key features to write Gradle scripts
  • Explore the important features of Gradle: task management, plugin management, and dependency management
  • Walkthrough various inbuilt Gradle plugins, such as Java, Scala, War, Ant, Maven, and many others
  • Master the migration techniques from build tools such as Ant and Maven into Gradle
  • Integrate Gradle with popular continuous integration tools such as Jenkins and TeamCity
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Publication date, Length, Edition, Language, ISBN-13
Publication date : Jul 31, 2015
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781783981366
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Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781783981366
Languages :
Concepts :
Tools :

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Table of Contents

11 Chapters
1. Getting Started with Gradle Chevron down icon Chevron up icon
2. Groovy Essentials for Gradle Chevron down icon Chevron up icon
3. Managing Task Chevron down icon Chevron up icon
4. Plugin Management Chevron down icon Chevron up icon
5. Dependency Management Chevron down icon Chevron up icon
6. Working with Gradle Chevron down icon Chevron up icon
7. Continuous Integration Chevron down icon Chevron up icon
8. Migration Chevron down icon Chevron up icon
9. Deployment Chevron down icon Chevron up icon
10. Building Android Applications with Gradle Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Empty star icon Empty star icon 3
(4 Ratings)
5 star 50%
4 star 0%
3 star 0%
2 star 0%
1 star 50%
Slowtrailrunner Aug 26, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I have been working with Gradle for about a year now, so I have some experience. I bought this book partly as a reference and partly as way to learn the what I don't know about Gradle. I have found this book to be a very good reference and I definitely appreciated the background information on Groovy. I will be recommending that we purchase this book for our team's library.
Amazon Verified review Amazon
CS Aug 26, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Bought this book to gain in-depth knowledge on Gradle. This book has great method of teaching Groovy programming language. You can build complete projects, test them yourself just by following the book. The book also talks about migrating and integrating strategies which is highly useful. You can also learn to make simple android apps which you can test using Gradle. Overall this book is very good if you want to learn Gradle entirely. Must Read.
Amazon Verified review Amazon
Jackson Michalak Jun 25, 2019
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
It appears there are no good books on the Gradle build system. Note that none of them, including this one, cover a recent version, not even close. Even if this book were covering the current version, it is quite superficial in its coverage. I prefer reading physical books, but this is far inferior to the free documentation online.
Amazon Verified review Amazon
Vincenzo Tarricone Nov 26, 2015
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
Banale e approssimativo. Spiega l'ovvio solo per "allungare il brodo" ma non impari nulla di più delle banalità che troveresti su google.
Amazon Verified review Amazon
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