Google App Engine Java and GWT Application Development

480 Pages·2010·7.9 MB·English

by  Daniel Guermeur

Google App Engine Java and
GWT Application Development
Build powerful, scalable, and interactive
web applications in the cloud
Daniel Guermeur
Amy Unruh
Google App Engine Java and
GWT Application Development
Copyright © 2010 Packt Publishing
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First published: November 2010
Production Reference: 1161110
Published by Packt Publishing Ltd.
32 Lincoln Road
Olton
Birmingham, B27 6PA, UK.
ISBN 978-1-849690-44-7
www.packtpub.com
Cover Image by Sujay Gawand ([email protected])
Credits
Authors Editorial Team Leader
Daniel Guermeur Aditya Belpathak
Amy Unruh
Project Team Leader
Lata Basantani
Reviewers
Dom Derrien
Yağız Erkan Project Coordinator
Vincila Colaco
Samuel Goebert
Ravi Sharma
Indexers
Monica Ajmera Mehta
Acquisition Editor
Rekha Nair
David Barnes
Proofreader
Development Editor
Kevin McGowan
Hyacintha D'Souza
Graphics
Technical Editors
Geetanjali Sawant
Paramanand N.Bhat
Namita Sahni
Production Coordinator
Arvindkumar Gupta
Copy Editor
Laxmi Subramanian
Cover Work
Arvindkumar Gupta
About the Authors
Daniel Guermeur is the founder and CEO of Metadot Corporation. He holds a
Diplome d'Ingenieur of Informatique from University of Technology of Compiegne
(France) as well as a Master in Photonics from Ecole Nationale Superieure de
Physique of Strasbourg (France). Before starting Metadot in 2000, he worked for oil
services companies including giant Schlumberger Ltd where he was in charge of
improving the worldwide IT infrastructure.
He has been developing large scale database-backed web applications since the very
beginning of the democratization of the Internet in 1995, including an open source
software content management system Metadot Portal Server, Mojo Helpdesk, a web-
based customer support application and Montastic, a popular website monitor service.
Thank you to my daughter Alexandra Guermeur and Cheryl Ridall
for their love and continuous support while writing this book. This
meant a lot to me. Cheryl, I miss you.
Amy Unruh currently does technology training and course development, with
a focus on web technologies. Previously, she has been a Research Fellow at the
University of Melbourne, where she taught web technologies and researched
robust distributed agent systems. She has worked at several startups, building web
applications using a variety of languages; served as adjunct faculty at the University
of Texas; and was a member of the Distributed Agents Program at MCC. She received
her Ph.D. in CS/AI from Stanford University, in the area of AI planning, and has a BS
degree in CS from UCSB. She has numerous publications, and has co-edited a book on
Safety and Security in Multiagent Systems.
Thanks to Moon, and to Wesley and Eleanor Unruh, without whose
love and support this book would not have been possible. And
thanks also to Daniel, for getting us started!
About the Reviewers
Dom Derrien joined AnotherSocialEconomy.com (ASE) as co-founder after
having worked for more than 15 years in the software development area.
Dom's responsibilities in ASE cover the architecture definition of its communication
engine and respective connectors enabling its multi-channel interfaces like e-mail,
Twitter, Facebook, Android, Adobe AIR, and others. Dom is also in charge of
defining the ASE public API (REST-based). He produces the vast majority of code
and corresponding tests for the implementation ported on Google App Engine. Dom
also coordinates the work of other contributors working on specific connectors as
well as reviewing web materials and contributing to pre-sales consulting, the internal
community site and business decision-making.
Prior to ASE, Dom worked for Compuware Corporation as Technical Consultant
in the Web application and Mobile application domains, to bootstrap new projects
in the Vantage product line. Before joining Compuware, as a Software Architect,
he worked on the development of a Web 2.0 client for Rational Portfolio Manager
enterprise project management server, at IBM Canada. Dom also worked at Oracle
Canada, as a Senior Developer, in the Oracle Collaboration Suite team, to build its
first Web 2.0 client, just at the time the corresponding technology was emerging.
Aside from his protected work for ASE, Dom shares some projects on github.com to
give back materials to the open source community (like a library for Amazon FPS on
GAE, utilities for internationalized Web applications, and others) and publishes his
own blog at domderrien.blogspot.com.
Dom is also active in the Diku Dilenga organization which aims to bring
microfinance services to the poorest in the Democratic Republic of the Congo.
His dream is to connect ASE to Diku Dilenga, to use modern communication
technologies at the service of microentrepreneurs.
Also important in his life is his family – his wife and two sons. They all enjoy
their peaceful life in Montreal, Quebec, Canada, and their practice of karate,
Chito-Ryu style.
Yağız Erkan is the Chief Technical Architect with DeCare Systems Ireland, an
Ireland-based software development company building highly-scalable, large
enterprise systems and retail sites. Before taking on an architectural role, he worked
as a software engineer for various companies in France.
Yağız studied in Galatasaray High School in Istanbul, Turkey, then he obtained
his MSc in Computer Science in Université Claude Bernard in Lyon, France. After
working several years as a software engineer in Lyon, he moved to Ireland and
joined DeCare Systems Ireland as a Technical Architect in 2000. He currently
leads a team of hands-on architects who ensure the most up-to-date and suitable
practices, technologies and tools are utilized, leading to the delivery of high quality
applications and solutions.
Even though Yağız's background is mainly Java and Web technologies, he has
worked on Microsoft .NET and mobile (iPhone and Android) projects. He has
already been mentioned in various books as a reviewer and he keeps an on-line
presence through blogging and social networking.
Samuel Goebert is a computer science master student at the University of Applied
Sciences Darmstadt, Germany. Goebert has over 7 years of experience in web related
development and associated technologies.
In his role as technology consultant for bigcurl (http://www.bigcurl.de) Goebert
is responsible for the overall design and execution of various products from
conception to launch including web applications, mobile applications, intranet
tools and custom API's.
He wrote his award winning bachelor thesis about scalable data delivery in local
area networks at Apple Inc. in California, which also awarded him with a students
scholarship from 2006 until 2009.
Goebert holds a Diploma from the School of Audio Engineering and received a
bachelors degree from the University of Applied Sciences Darmstadt, Germany in
Computer Science.
He is currently working on receiving his master degree in Computer Science in the
field of restoring communications for the population of post disaster areas with
autonomously deploying cell phone towers.
Ravi Sharma has a B.Tech (Computer Science) from Y.M.C.A Institute of
Engineering, Faridabad and has worked in banking and higher studies. He has
8 years of experience in java especially low latency applications.He runs his own
company, NextInfotech (www.nextinfotech.com) and also works as a consultant.
Table of Contents
Preface 1
Chapter 1: Introduction 7
Overview of the chapter 8
Introduction to Google App Engine 8
The Datastore 9
App Engine's scalable services 9
Java App Engine runtime and the application development environment 10
GAE/J and the Eclipse IDE 10
App Engine application hosting 11
App Engine "surprises" for new developers 11
Introduction to GWT 12
GWT UI support 13
Other GWT features 14
GWT's RPC API 14
GWT with GAE 14
The GWT/GAE Eclipse plugin 15
GWT support for Java 15
Recommended GWT background 16
Example application: Connectr 16
A look ahead 19
Online resources 19
GAE and GWT galleries 20
Documentation, blogs, and discussion groups 20
Summary 21
Chapter 2: Using Eclipse and the Google Plugin 23
Installing the plugin and supporting software 24
Installing the Java SDK 24
Installing Java on Mac OS X 25
Installing Java on other platforms 26
Table of Contents
Installing Eclipse 26
Installing the Google plugin 26
Updating the Google plugin 28
Developing your application in Eclipse 29
Creating a new web application project in Eclipse 29
First look: The anatomy of a web application project 30
The Google plugin wizards and helpers 33
Running and debugging your application 34
Running your application in Development Mode 35
Developing the application in debug mode 35
Development Mode and the GWT browser plugin 36
Defining a run or debug configuration 38
Debugging 38
Compiling your GWT code for production mode 40
Deploying your application 41
Registering and setting an application ID for your application 41
How to set the application ID and version for a project 43
Uploading and deploying your application 44
Your App Engine Admin Console 45
Importing an existing application 46
Adding the Google SDKs to your project's build path 47
Adding third-party JAR files 47
Managing multiple Google SDKs 48
Running Google's demo apps in Eclipse 48
Summary 49
Chapter 3: Building the Connectr User Interface with GWT 51
Installing the (first version of) the Connectr project in Eclipse 52
AJAX and its benefits 56
Why AJAX apps are the way forward 56
AJAX apps minimize traffic and workload both on the client and the server 57
Challenges associated with AJAX programming and how GWT
solves them 58
JavaScript browser's implementation is not consistent 59
Mastering JavaScript—an uphill battle 60
How GWT comes to the rescue to make developers more efficient 61
Google Web Toolkit overview—modern tools for modern developers 62
GWT user interface building blocks 63
Building the Connectr application—the user interface 64
User interface design elements of Connectr 65
Coding the Connectr user interface 66
Introducing UiBinder to increase productivity 66
Declarative UiBinder versus procedural Java—let's compare 67
[ ii ]
Table of Contents
Implementing the application layout with UiBinder 70
Tying the view to the Java code 73
Adding custom widgets to UiBinder 74
Adding CSS styles to the application 75
Implementing CSS styles in a global CSS file 77
Adding a logo to the application 77
Catching mouse and keyboard events 78
Grouping CSS files and images for faster speed with ClientBundle 79
Creating a ClientBundle 80
Using image resources in Connectr 81
Automatically checking CSS styles at compile time with CssResource 82
Getting data from the server using GWT RPC 82
Creating the login service 83
Implementing the server-side login service 84
Creating the asynchronous interface 85
Invoking the login service 85
Catching exceptions 86
Summary 87
Chapter 4: Persisting Data: The App Engine Datastore 89
Introduction 89
The Connectr server-side object model 90
The Datastore 91
Datastore entities and their properties 91
Entity keys 93
Datastore queries and indexes 94
Queries are supported by indexes 94
App Engine queries are fast 95
The Datastore versus a relational database 95
JDO 96
Setting up JDO 97
Creating Connectr's data models 97
The PersistenceManager and the PersistenceManagerFactory 98
Making data classes persistable 99
Class and field annotations 99
Persistable field types 101
Core value types 102
Collections and multi-valued properties 103
Datastore keys and JDO key fields 105
Defining keys and core value type fields for Friend and UserAccount 109
Referencing complex objects 111
Serializable objects and serialized fields 112
Embedded classes 115
[ iii ]