Adam L. Davis
Learning Groovy 3Java-Based Dynamic Scripting2nd ed.
Adam L. Davis
New York, NY, USA
ISBN 978-1-4842-5057-0e-ISBN 978-1-4842-5058-7
https://doi.org/10.1007/978-1-4842-5058-7
© Adam L. Davis 2019
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed.
Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights.
While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein.
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To my parents, to whom I owe everything in ways large and small.

To my children, who mean the world to me.

To my wife, for putting up with me and supporting me.

About This Book

This book is organized into several chapters, starting from the most basic concepts. If you already understand a concept, you can safely move ahead to the next chapter. Although this book concentrates on Groovy, it also refers to other languages, such as Java, Scala, and JavaScript.

As the title suggests, this book is about learning Groovy but will also cover related technology, such as build tools and web frameworks.

Assumptions

This book assumes the reader already is familiar with Java syntax and basic programming ideas.

Icons

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If you see text stylized like this, it is extra information that you might find helpful.

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Text stylized this way is usually a reference to additional information for the curious reader.

../images/426440_2_En_BookFrontmatter_Figf_HTML.gif Warnings

Text like this is caution for the wary reader—many have fallen on the path of computer programming.

../images/426440_2_En_BookFrontmatter_Figg_HTML.gif Exercises

This is an exercise. We learn by doing. These are highly recommended.

Acknowledgments

Thank you to the following people without whom this book would not have been possible: my wife, for putting up with me working on yet another book; my editors, for all of the much needed editing; and my technical reviewer, Manual Jordan Elera, for doing the vital work of making sure everything in this book is accurate. Thank you to all of the developers behind Groovy and related projects written about in this book: Paul King, Cédric Champeau, Daniel Sun, and the rest of the Groovy team; Peter Niederwieser, the creator of Spock; Luke Daley and the rest of the contributors behind Ratpack; Adam Murdoch, and the rest of the developers behind Gradle; Graeme Rocher and the rest of the team behind Grails and Micronaut; and anyone else I’ve left out. Without these great tools and frameworks (and the openness, helpfulness, and friendliness of the community), programming would be much less enjoyable.

Table of Contents

Part 1: Getting Groovy
Chapter 1:​ Software to Install 3
Java/​Groovy 3
Trying It Out 4
Others 6
Code on GitHub 6
Chapter 2:​ Groovy 101 7
What Is Groovy?​ 7
Compact Syntax 8
Dynamic def 9
List and Map Definitions 9
Groovy GDK 10
Everything Is an Object 11
Easy Properties 11
GString 12
Closures 12
A Better Switch 14
Meta-Programming 15
Static Type Checking 16
Elvis Operator 17
Safe Dereference Operator 18
A Brief History 18
Groovy 1.​8 18
Groovy 2.​0 19
Groovy 2.​1 20
Groovy 2.​2 20
Groovy 2.​3 21
Groovy 2.​4 21
Groovy 2.​5 22
Groovy 2.​6 23
Groovy 3.​0 23
Summary 25
Chapter 3:​ Tools 27
Console 27
Compilation 28
Shell 28
Documentation 29
Chapter 4:​ GDK 31
Collections 31
Java 8 Streams 32
Spread 32
GPath 33
IO 33
Files 34
URLs 35
Ranges 36
Utilities 37
ConfigSlurper 38
JsonBuilder and JsonSlurper 38
Expando 39
ObservableList/​Map/​Set 40
Chapter 5:​ Coming from Java 43
Default Method Values 43
Equals, HashCode, and More 44
Regex Pattern Matching 45
Missing Java Syntax 46
Optional Semicolon 46
Optional Parenthesis Sometimes 47
Where Are Generics?​ 48
Groovy Numbers 48
Boolean-Resolution 49
Map Syntax 49
Summary 50
Part 2: Advanced Groovy
Chapter 6:​ Groovy Design Patterns 53
Strategy Pattern 53
Meta-Programming 54
Meta-Class 55
Categories 55
Missing Methods 57
Delegation 58
Chapter 7:​ DSLs 61
Closure with Delegate 61
Command Chains 63
Overriding Operators 64
Missing Methods and Properties 67
Extension Modules 70
Chapter 8:​ Traits 73
Defining Traits 73
Using Traits 74
Summary 75
Chapter 9:​ Functional Programming 77
Functions and Closures 78
Using Closures 79
Map/​Filter/​And So On 79
Immutability 83
Groovy Fluent GDK 86
Groovy Curry 87
Method Handles 88
Tail Recursion 89
Summary 90
Chapter 10:​ Groovy GPars 91
Getting Started 91
Parallel Map Reduce 92
Actors 92
More GPars 95
Part 3: The Groovy Ecosystem
Chapter 11:​ Groovy Awesomeness 99
Web and UI Frameworks 99
Grails 99
Micronaut 99
Griffon 100
Vert.​x 100
Ratpack 100
Cloud Computing Frameworks 100
Gaelyk 100
Caelyf 101
Build Frameworks 101
Gradle 101
Gant 101
Testing Frameworks/​Code Analysis 101
Spock 102
Codenarc 102
Concurrency 102
GPars 102
RxGroovy 102
Others 103
SDKMAN 103
Lazybones 103
GrooCSS 103
Chapter 12:​ Gradle 105
Projects and Tasks 105
Plugins 107
Configuring a Task 107
Extra Configuration 108
Dependencies 108
Gradle Properties 110
Multiproject Builds 110
File Operations 112
Exploring 113
Completely Groovy 113
Summary 113
Chapter 13:​ Grails 115
Quick Overview of Grails 115
Configuration 119
Plugins 120
GSP and Taglibs 121
Serving JSON or XML 121
UrlMappings 123
Short History of Grails 124
Grails 2.​0 124
Grails 2.​1 125
Grails 2.​2 126
Grails 2.​3 126
Grails 2.​4 127
Grails 2.​5 127
Grails 3.​1.​x 128
Grails 4 129
Testing 129
Cache Plugin 130
Chapter 14:​ Spock 131
Spock Basics 131
A Simple Test 132
Mocking 133
Lists or Tables of Data 134
Expecting Exceptions 135
Summary 135
Chapter 15:​ Ratpack 137
Script 138
Gradle 138
Ratpack Layout 139
Handlers 140
Rendering 142
Groovy Text 144
Handlebars and Thymeleaf 144
JSON 146
Bindings 148
Blocking 149
Configuration 150
Testing 151
Summary 154
Index 155

About the Author and About the Technical Reviewer

About the Author

Adam L. Davis
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makes software. He has spent many years developing in Java (since Java 1.2) and has enjoyed using Spring and Hibernate. Since 2006 he’s been using Groovy and Grails in addition to Java to create SaaS web applications that help track contracts and finances for large institutions (among other things) at The Solution Design Group, Inc. Adam has a master’s and a bachelor’s degree in Computer Science from Georgia Tech. He attends many conferences, has authored several books, and sometimes speaks at conferences and his local Java User Group.

You can find out more at his web site: www.adamldavis.com .

He currently resides in Central Florida with his wife, two small children, and their dog.

 

About the Technical Reviewer

Manuel Jordan Elera
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is an autodidactic developer and researcher who enjoys learning new technologies for his own experiments and creating new integrations.

Manuel won the 2010 Springy Award—Community Champion and Spring Champion 2013. In his little free time, he reads the Bible and composes music on his guitar. Manuel is known as dr_pompeii . He has tech-reviewed numerous books for Apress, including Pro Spring, Fourth Edition (2014), Practical Spring LDAP (2013), Pro JPA 2, Second Edition (2013), and Pro Spring Security (2013).

Read his 13 detailed tutorials about many Spring technologies, contact him through his blog at www.manueljordanelera.blogspot.com , and follow him on his Twitter account @dr_pompeii .

 
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