Google, Amazon, and Beyond: Creating and Consuming Web Services

353 Pages·2003·2.09 MB·English

by  Alexander Nakhimovsky

*1313_Ch00_FINAL 10/27/03 11:44 AM Page i
Google, Amazon,
and Beyond:
Creating and Consuming
Web Services
ALEXANDER NAKHIMOVSKY AND TOM MYERS
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xii
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xiii
About the Authors
Alexander Nakhimovskyreceived an MA in mathematics from
Leningrad University (1972) and a Ph.D in linguistics from Cornell
University (1979) with a graduate minor in computer science. He
has been teaching computer science at Colgate University since
1985. He is also the author of books and articles on linguistics
and artificial intelligence—the foundational concepts of the
Semantic Web.
Tom Myersstudied physics in Bogota and Buenos Aires before
receiving his BA from St. John’s College, Santa Fe (1975) and a
PhD in computer science from the University of Pennsylvania
(1980). Recently, he has been working on Java and XML projects,
especially database work in Java using J2EE. He is also the
author of a book and several articles on theoretical computer
science.
xiii
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xiv
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xv
About the
Technical Reviewer
As Web Services Evangelist for Amazon.com, Jeff Barrfocuses
on creating developer awareness for the Amazon software
platform. He has a longstanding interest in Web Services and
programmatic information interchange. Jeff has held devel-
opment and management positions at KnowNow, eByz,
Akopia, and Microsoft, and was a co-founder of Visix Software.
Jeff’s interests include collecting and organizing news feeds
using his site, www.syndic8.com. He holds a Bachelor’s degree in
computer science from the American University and has done graduate work in
computer science at the George Washington University.
xv
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xvi
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xvii
Acknowledgments
As always, we are grateful to the excellent editorial staff at Apress, to our families,
and to the people who came up with all this new stuff for us to learn and write
about.
xvii
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xviii
*1313_Ch00_FINAL 10/27/03 11:44 AM Page xix
Introduction
What Is This Book About?
This is a book about Web Services. Web Services are still more like a movement
than a mature technology. The movement is motivated by a vision of a semi-auto-
mated Web that can support long chains of interactions between autonomous
agents. There are three important components to that vision. One is interoperabil-
ity: a service can have clients (agents) from any platform, in any language. Another
is autonomy: an agent can discover the services it needs from their published
descriptions that include both whatthe service can do and howit does it (the
interfaces of available actions). The third is (semi) automatic code creation: one
description can be used by a development framework to automate the creation
of code for clients and by the services themselves. As of today, interoperability is
close to full realization, with only occasional glitches; autonomy is a distant vision;
code creation is useful but it still has problems. Interoperability has been achieved
in part by using an XML-based high-level protocol (SOAP) for message exchanges
between clients and services. As long as the client can produce messages in the
right format, it doesn’t matter what language they're written in or on what platform
they run.
The first three chapters of our book show how to write platform-independent
Web Services clients in Javascript and Java running from within a browser (IE6 or
Mozilla). The services to which our clients connect are for the most part from
Google and Amazon, the first companies of substantial size to open access via Web
Services to their proprietary information and functionality. To illustrate the gener-
ality of approach and possible integration, we use the same techniques and the
same clients to connect to other services as well, combining the results in a single
application.
Chapters 4 and 5 continue with the idea of integration, but this time we
develop a service of our own (a local Book Club) and show how it can be inte-
grated with other services (like Amazon). Chapter 5 adds some security to our
service but it also introduces an important new topic: Web Services without SOAP.
There is a large movement and a well-motivated argument that SOAP is not a good
idea, and that the same benefits of interoperability can be achieved using just
HTTP. The movement is generally known as REST (Representational State Trans-
fer), and you’ll find out about it in Chapter 5 when we present a REST version of
our Book Club service. (We are helped here by Amazon’s wise decision to offer
both SOAP and REST interfaces to their Web Services.)
xix