Kenneth A. Kousen FOREWORD BY Guillaume Laforge MANNING Making Java Groovy Making Java Groovy KENNETH A. KOUSEN MANNING SHELTER ISLAND For online information and ordering of this and other Manning books, please visit www.manning.com. The publisher offers discounts on this book when ordered in quantity. For more information, please contact Special Sales Department Manning Publications Co. 20 Baldwin Road PO Box 261 Shelter Island, NY 11964 Email: [email protected] ©2014 by Manning Publications Co. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Photographs in this book were created by Martin Evans and Jordan Hochenbaum, unless otherwise noted. Illustrations were created by Martin Evans, Joshua Noble, and Jordan Hochenbaum. Fritzing (fritzing.org) was used to create some of the circuit diagrams. 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Development editor: Cynthia Kane 20 Baldwin Road Copyeditor: Melinda Rankin PO Box 261 Proofreader: Melody Dolab Shelter Island, NY 11964 Typesetter: Dennis Dalinnik Cover designer: Marija Tudor ISBN: 9781935182948 Printed in the United States of America 1 2 3 4 5 6 7 8 9 10 – MAL – 19 18 17 16 15 14 13 To my father, Morton Kousen, MD, who taught me everything I know about dedication, persistence, and facing the future with a positive and upbeat attitude, despite whatever pain and difficulties lay ahead. He will always be my best example of what a man should be. brief contents PART 1 UP TO SPEED WITH GROOVY. ........................................1 1 ■ Why add Groovy to Java? 3 2 ■ Groovy by example 18 3 ■ Code-level integration 46 4 ■ Using Groovy features in Java 64 PART 2 GROOVY TOOLS ..........................................................91 5 ■ Build processes 93 6 ■ Testing Groovy and Java projects 126 PART 3 GROOVY IN THE REAL WORLD....................................165 7 ■ The Spring framework 167 8 ■ Database access 199 9 ■ RESTful web services 227 10 ■ Building and testing web applications 257 vii contents foreword xv preface xvii acknowledgments xix about this book xxii about the cover illustration xxvi PART 1 UP TO SPEED WITH GROOVY . ............................1 Why add Groovy to Java? 3 1 1.1 Issues with Java 4 Is static typing a bug or a feature? 5 ■ Methods must be in a class, even if you don’t need or want one 7 ■ Java is overly verbose 10 Groovy makes testing Java much easier 11 ■ Groovy tools simplify your build 13 1.2 Groovy features that help Java 14 1.3 Java use cases and how Groovy helps 15 Spring framework support for Groovy 16 ■ Simplified database access 16 ■ Building and accessing web services 16 Web application enhancements 17 1.4 Summary 17 ix x CONTENTS Groovy by example 18 2 2.1 Hello, Groovy 19 2.2 Accessing Google Chart Tools 19 Assembling the URL with query string 20 ■ Transmitting the URL 23 ■ Creating a UI with SwingBuilder 24 2.3 Groovy Baseball 26 Database data and Plain Old Groovy Objects 29 Parsing XML 35 ■ HTML builders and groovlets 42 2.4 Summary 45 Code-level integration 46 3 3.1 Integrating Java with other languages 46 3.2 Executing Groovy scripts from Java 48 Using JSR223 scripting for the Java Platform API 50 Working with the Groovy Eval class 56 ■ Working with the GroovyShell class 57 ■ Calling Groovy from Java the easy way 59 ■ Calling Java from Groovy 62 3.3 Summary 63 Using Groovy features in Java 64 4 4.1 Treating POJOs like POGOs 65 4.2 Implementing operator overloading in Java 67 4.3 Making Java library classes better: the Groovy JDK 71 4.4 Cool AST transformations 74 Delegating to contained objects 74 ■ Creating immutable objects 76 ■ Creating singletons 81 4.5 Working with XML 82 4.6 Working with JSON data 89 4.7 Summary 90 PART 2 GROOVY TOOLS ..............................................91 Build processes 93 5 5.1 The build challenge 94 5.2 The Java approach, part 1: Ant 95 CONTENTS xi 5.3 Making Ant Groovy 97 The <groovy> Ant task 97 ■ The <groovyc> Ant task 98 Writing your build in Groovy with AntBuilder 100 Custom build scripts with Gant 102 ■ Ant summary 104 5.4 The Java approach, part 2: Maven 105 The Groovy-Eclipse plugin for Maven 106 The GMaven project 110 ■ Maven summary 113 5.5 Grapes and @Grab 114 5.6 The Gradle build system 117 Basic Gradle builds 118 ■ Interesting configurations 122 5.7 Summary 124 Testing Groovy and Java projects 126 6 6.1 Working with JUnit 128 A Java test for the Groovy implementation 131 A Groovy test for the Java implementation 133 A GroovyTestCase test for a Java implementation 134 6.2 Testing scripts written in Groovy 137 Useful subclasses of GroovyTestCase: GroovyShellTestCase 139 Useful subclasses of GroovyTestCase: GroovyLogTestCase 141 6.3 Testing classes in isolation 142 Coerced closures 144 ■ The Expando class 146 StubFor and MockFor 151 6.4 The future of testing: Spock 156 The Search for Spock 156 ■ Test well, and prosper 157 Data-driven specifications 159 ■ The trouble with tribbles 161 Other Spock capabilities 163 6.5 Summary 164 PART 3 GROOVY IN THE REAL WORLD ........................165 The Spring framework 167 7 7.1 A Spring application 168 7.2 Refreshable beans 175 7.3 Spring AOP with Groovy beans 179 7.4 Inline scripted beans 185 7.5 Groovy with JavaConfig 186 xii CONTENTS 7.6 Building beans with the Grails BeanBuilder 190 7.7 Summary 197 Database access 199 8 8.1 The Java approach, part 1: JDBC 200 8.2 The Groovy approach, part 1: groovy.sql.Sql 203 8.3 The Java approach, part 2: Hibernate and JPA 208 8.4 The Groovy approach, part 2: Groovy and GORM 213 Groovy simplifications 213 ■ Grails Object-Relational Mapping (GORM) 213 8.5 Groovy and NoSQL databases 220 Populating Groovy vampires 220 ■ Querying and mapping MongoDB data 223 8.6 Summary 226 RESTful web services 227 9 9.1 The REST architecture 229 9.2 The Java approach: JAX-RS 230 JAX-RS resource and tests 232 9.3 Implementing JAX-RS with Groovy 239 9.4 RESTful Clients 242 9.5 Hypermedia 243 A simple example: Rotten Tomatoes 244 ■ Adding transitional links 246 ■ Adding structural links 249 ■ Using a JsonBuilder to control the output 250 9.6 Other Groovy approaches 253 Groovlets 253 ■ Ratpack 255 ■ Grails and REST 255 9.7 Summary 256 Building and testing web applications 257 10 10.1 Groovy servlets and ServletCategory 258 10.2 Easy server-side development with groovlets 263 A “Hello, World!” groovlet 264 ■ Implicit variables in groovlets 266 CONTENTS xiii 10.3 Unit- and integration-testing web components 268 Unit-testing servlets with Spring 268 ■ Integration testing with Gradle 270 ■ Automating Jetty in the Gradle build 272 Using an integration-test source tree 274 10.4 Grails: the Groovy “killer app” 277 The quest for the holy Grails 279 10.5 Summary 288 appendix A Installing Groovy 289 appendix B Groovy by feature 295 appendix C Soap-based web services available online at manning.com/kousen index 327 foreword When we designed the Groovy language almost 10 years ago, our main goal was to cre- ate a language that is a complement to Java, a close companion, that Java developers would be familiar with and could learn easily. The idea was to empower users to be more productive by removing the boilerplate of Java, and to simplify their program- ming lives by giving them compelling and straightforward APIs to work with. I’m proud to say that the Groovy team attained that goal, making Groovy the most popu- lar alternative language for the Java platform. Along the way, and by virtue of its nature, Groovy was adopted by Java developers in a number of ways. For example, it was introduced in Java projects for testing pur- poses, because the Groovy syntax is light and readable but still resembles that of Java. For interacting with XML payloads, web services, or databases, Groovy provides handy and elegant wrappers around the Java Development Kit that make those tasks a breeze. And for writing business rules in Java applications, Groovy shines, thanks to its metaprogramming capabilities and its concise and expressive grammar. I had the pleasure and honor of meeting Ken a few years ago at a Groovy confer- ence, and our paths have crossed several times since then. Among other topics, we talked about how Groovy is a great fit for various assignments that Java developers have to accomplish every day but that are painful with the heavier-weight Java. So when Ken told me that he envisioned writing a book on this same topic, I was excited about the idea! What makes this book stand out of the pack of Groovy books is its focus on the tasks that Java developers must tackle every day. How can I more easily parse or emit xv xvi FOREWORD XML or JSON documents? How can I test my Java code with a more expressive syntax? How can I talk to my database without the error-prone JDBC API? How can I build and test Java applications more efficiently? In this book, Ken answers all of these questions and shows you a Groovy solution for each of those chores.