Rails for Java Developers

323 Pages·2007·2.01 MB·English

by  Stuart Halloway, Justin Gehtland

What readers are saying about Rails for Java Developers
Every Java developer should be exposed to ideas from different lan-
guages, and Ruby/Rails is a wellspring of good ideas. Read this
book—it will help you learn Ruby and Rails, and give you new ideas
transferableto Java.
David Bock
Technical Director, Federal and Commercial Division, FGM
Inc.
Stuart and Justin have pulled off what I once thought was an impos-
sible feat: consolidating all the knowledge that a Java developer needs
to understand Ruby on Rails. Until this book, you would have to read
at least three books (and thousands of pages) to get the same under-
standing encapsulated in this excellent text. They clearly understand
both sides of the equation (RoR and Java), which allows them to cut
through irrelevancies and hone in on the important topics. This book
should be required reading for more than just the people learning
Rails: every Java developer will benefit from learning the important
lessons that Rails teaches.
Neal Ford
Application Architect/Developer, Thoughtworks
If you are a Java developer and you want to explore Ruby on Rails,
this is the book to get. Justin and Stu do a masterful job of revealing
the intricacies of Ruby and Ruby on Rails from a Java developer’s per-
spective. Not only that, this book is extremely well written,and is a
pleasure to read.
David Geary
Author of Graphic Java Swing and co-author of Core
JavaServer Faces
Stu and Justin offer the Java developer the unique opportunity to
“get” Rails by presenting the Rails stack from a perspective that’s
familiar and comfortable. In doing so, they prove that Rails and Java
don’t have to be mutually exclusive.
Ted Neward
Author of Effective Enterprise Java
If you are a Java developer trying to learn Rails, this book is the place
to start. There is no better resource for quickly coming up to speed
with Rails, Ruby, Rake, and ActiveRecord.
Mark Richards
Senior IT Architect, IBM
To hear some tell it, there’s tension and rivalry between the Java and
Rails web development camps, but that’s hard to see from whereI
stand. Most of the happy Rails developers I know have a long history
as Java programmers, and while we love Java for what it does well,
web development in Java leaves a lot to be desired. Rails is a delight-
ful breath of fresh air, and I’m confident this book will open the eyes
of a lot of other Java developers who are looking for a nicer way to
build web applications.
Glenn Vanderburg
Independent Ruby and Java consultant

Rails for Java Developers
Stuart Halloway
Justin Gehtland
The Pragmatic Bookshelf
Raleigh,NorthCarolina Dallas,Texas
Many of the designations used by manufacturers and sellers to distinguish their prod-
uctsareclaimedastrademarks.Wherethosedesignationsappearinthisbook,andThe
Pragmatic Programmers, LLC was aware of a trademark claim, the designations have
been printed in initial capital letters or in all capitals. The Pragmatic Starter Kit, The
PragmaticProgrammer,PragmaticProgramming,PragmaticBookshelfandthelinkingg
devicearetrademarksofThePragmaticProgrammers,LLC.
Every precaution was taken in the preparation of this book. However, the publisher
assumesnoresponsibility for errorsor omissions,or for damagesthatmay result from
theuseofinformation(includingprogramlistings)containedherein.
Our Pragmatic courses, workshops, and other products can help you and your team
create better software and have more fun. For more information, as well as the latest
Pragmatictitles,pleasevisitusat
http://www.pragmaticprogrammer.com
Copyright©2007ThePragmaticProgrammersLLC.
Allrightsreserved.
Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmit-
ted, in any form, or by any means, electronic,mechanical,photocopying, recording, or
otherwise,withoutthepriorconsentofthepublisher.
PrintedintheUnitedStatesofAmerica.
ISBN-10:0-9776166-9-X
ISBN-13:978-0-9776166-9-5
Printedonacid-freepaperwith85%recycled,30%post-consumercontent.
Firstprinting,February,2007
Version:2007-2-12
Contents
Foreword 11
Preface 13
1 Getting Started with Rails 20
1.1 Setting Up Ruby and Rails . . . . . . . . . . . . . . . . . 20
1.2 Rails App in Fifteen Minutes . . . . . . . . . . . . . . . . 21
1.3 The Rails Development Cycle . . . . . . . . . . . . . . . . 25
1.4 Finding Information in Online Documentation . . . . . . 28
1.5 Editors and IDEs . . . . . . . . . . . . . . . . . . . . . . . 29
1.6 Running the Samples . . . . . . . . . . . . . . . . . . . . 30
1.7 Rails Environments . . . . . . . . . . . . . . . . . . . . . 32
1.8 How Rails Connects to Databases . . . . . . . . . . . . . 35
1.9 Rails Support Scripts . . . . . . . . . . . . . . . . . . . . 36
2 Programming Ruby 38
2.1 Primitive Types . . . . . . . . . . . . . . . . . . . . . . . . 38
2.2 Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.3 Objects and Methods . . . . . . . . . . . . . . . . . . . . 44
2.4 Collections and Iteration . . . . . . . . . . . . . . . . . . 47
2.5 Control Flow . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.6 Defining Classes . . . . . . . . . . . . . . . . . . . . . . . 57
2.7 Identity and Equality . . . . . . . . . . . . . . . . . . . . 63
2.8 Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . 65
2.9 Controlling Access with Access Specifiers . . . . . . . . 67
2.10 Raising and Handling Exceptions . . . . . . . . . . . . . 69
3 Ruby Eye for the Java Guy 72
3.1 Extending Core Classes . . . . . . . . . . . . . . . . . . . 72
3.2 Mutable and Immutable Objects . . . . . . . . . . . . . . 74
3.3 Packages and Namespaces . . . . . . . . . . . . . . . . . 76
3.4 Deploying Code . . . . . . . . . . . . . . . . . . . . . . . . 79
3.5 Delegation . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
CONTENTS 8
3.6 Polymorphism and Interfaces. . . . . . . . . . . . . . . . 85
3.7 Duck Typing . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.8 Mixins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.9 Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4 Accessing Data with ActiveRecord 96
4.1 Getting Connected . . . . . . . . . . . . . . . . . . . . . . 97
4.2 Managing Schema Versions with Migrations . . . . . . . 100
4.3 Mapping Data to Classes . . . . . . . . . . . . . . . . . . 103
4.4 Create, Read, Update, and Delete: Access Patterns . . . 106
4.5 Validating Data Values . . . . . . . . . . . . . . . . . . . 113
4.6 Lifecycle Callbacks . . . . . . . . . . . . . . . . . . . . . . 116
4.7 Associations and Inheritance . . . . . . . . . . . . . . . . 119
4.8 Transactions, Concurrency, and Performance . . . . . . 125
4.9 Conserving Resources with Connection Pooling . . . . . 131
4.10 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5 Coordinating Activities with ActionController 133
5.1 Routing Basics: From URL to Controller+Method . . . . 134
5.2 List and Show Actions: The R in CRUD . . . . . . . . . . 136
5.3 Create, Update, and Delete Actions . . . . . . . . . . . . 140
5.4 Tracking User State with Sessions . . . . . . . . . . . . . 144
5.5 Managing Cross-Cutting Concerns with Filtersand Verify147
5.6 Routing in Depth . . . . . . . . . . . . . . . . . . . . . . . 151
5.7 Logging, Debugging, and Benchmarking . . . . . . . . . 153
5.8 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
6 Rendering Output with ActionView 167
6.1 Creating Basic .rhtml Files . . . . . . . . . . . . . . . . . 168
6.2 Minimizing View Code with View Helpers . . . . . . . . . 169
6.3 WritingCustom Helpers . . . . . . . . . . . . . . . . . . . 170
6.4 Reuse with Layouts and Partials . . . . . . . . . . . . . . 172
6.5 Building HTML Forms . . . . . . . . . . . . . . . . . . . . 174
6.6 Building HTML with Markaby . . . . . . . . . . . . . . . 178
6.7 Caching Pages, Actions, and Fragments . . . . . . . . . 180
6.8 Creating Dynamic Pages with Ajax. . . . . . . . . . . . . 184
6.9 Rendering JavaScript with RJS . . . . . . . . . . . . . . 191
6.10 Black-Box Testing with Selenium . . . . . . . . . . . . . 192
6.11 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 196
6.12 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
CONTENTS 9
7 Testing 198
7.1 Getting Started with Test::Unit . . . . . . . . . . . . . . . 199
7.2 Rails Testing Conventions. . . . . . . . . . . . . . . . . . 206
7.3 Rails Extensions to Test::Unit . . . . . . . . . . . . . . . 212
7.4 Integration Testing . . . . . . . . . . . . . . . . . . . . . . 216
7.5 Rails Testing Examples . . . . . . . . . . . . . . . . . . . 218
7.6 Measuring Code Coverage with rcov . . . . . . . . . . . . 222
7.7 Testing Interactions with Mock Objects . . . . . . . . . . 225
7.8 Reducing Dependencies with Stub Objects . . . . . . . . 229
7.9 Advanced Considerations . . . . . . . . . . . . . . . . . . 230
7.10 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
8 Automating the Development Process 233
8.1 Rake Basics . . . . . . . . . . . . . . . . . . . . . . . . . . 234
8.2 Setting Rake Options: It’s Just Ruby . . . . . . . . . . . 236
8.3 Custom Rake Tasks: It’s Just Ruby . . . . . . . . . . . . 238
8.4 Using Rake in Rails Applications . . . . . . . . . . . . . . 240
8.5 Continuous Integration with Cerberus . . . . . . . . . . 243
8.6 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
9 Creating and Invoking Web Services 247
9.1 RESTful Web Services . . . . . . . . . . . . . . . . . . . . 248
9.2 SOAP Web Services. . . . . . . . . . . . . . . . . . . . . . 255
9.3 YAML and XML Compared . . . . . . . . . . . . . . . . . 261
9.4 JSON and Rails . . . . . . . . . . . . . . . . . . . . . . . . 265
9.5 XML Parsing . . . . . . . . . . . . . . . . . . . . . . . . . 266
9.6 Ruby XML Output . . . . . . . . . . . . . . . . . . . . . . 275
9.7 Creating XML with Builder . . . . . . . . . . . . . . . . . 276
9.8 Curing Your Data Headache . . . . . . . . . . . . . . . . 278
9.9 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
10 Security 282
10.1 Authentication with the acts_as_authenticated Plugin . 283
10.2 Authorization with the Authorization Plugin . . . . . . . 285
10.3 Testing Authentication and Authorization . . . . . . . . 290
10.4 Preventing the Top-Ten Web Security Flaws . . . . . . . 293
10.5 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
A Java to Ruby Dictionary 303
CONTENTS 10
B Bibliography 306
C Structure of a Rails Project 307
Index 309