Table Of ContentPerspectives on Web Services
Olaf Zimmermann Mark Tomlinson
Stefan Peuser
Perspectives on
Web Services
Applying SOAP, WSDL and UDD!
to Real-World Projects
With 188 Figures
<Zl
Springer
Olaf Zimmermann
Mark Tomlinson
Stefan Peuser
[email protected]
Library of Congress Cataloging-in-Publication Data applied for
2nd corrected printing 2005
ISBN 978-3-642-62468-1 ISBN 978-3-642-55514-5 (eBook)
DOI 10.1007/978-3-642-55514-5
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Foreword
Looking back over the brief but substantial history of Web-centric systems for the
enterprise, it is possible to identifY the evolution of distinct architectural styles.
The earliest systems were relatively sialic bUllhen were quickly followed by much
more dynamic ones that scattered behavior throughout the system in the ronn of
applets and scripts. Unfortunately, such systems were often quite fragile in that
there were so many interdependent moving parts that CQuid be changed independ
ently from one aonther. The evolution of J2EE and then NET provided better fa
cilities for cornponentization as well as common mechanisms for messaging and
transactions. However, these platfomls introduced another set of problems by each
providing homogeneous solutions in what is practically a very heterogeneous
space, namely, enterprise systems requiring the presence of both J2EE and .NET
as well as legacy systems of more ancient origins.
The emergence of service~oriented architectures for Web·centric enterprise sys·
tems is the next stage in this evolution, reflecting the need for higher levels of ab
straction that transcend specific platforms. Service-oriented architectures offer
even better mechanisms for componemization, mechanisms that provide a stronger
separation of concerns while pennitting a balanced distribution of ersponsibilities
throughout the system.
Over the past couple of years, I've been helping a handful of projects make the
move to Web service·oriented architectures, and I certainly wish I'd had this book
at my disposal, for it would have definitely made my life a whole lot easier.
Olaf, Mark and Stefan are well-positioned to offer their perspectives on Web
services, simply because they are collectively very experienced in building such
systems. In their roles at IBM Global Services and IBM Software Group, they
have worked on av ariety of service-oriented architectures, and that deep experi
ence shows through in this book, which is filled with pragmatic lessons· learned,
rules of thumb, and guidance on what to do, what not to do and w hat issues to
consider.
The authors cover virtually everything you need to consider when building, de·
ploying and running a services·oriented enterprise system. I am particularly im
pressed by their exposition of this material in the fonn ofmuhiple perspectives: no
interesting enterprise system can be understood from just one viewpoint, and thus
the authors have considered the sisues of Web services from each of the view
points that is gennane to an enterprise system. For the architect, we see coverage
of the patterns and design decision tradeofTs among services; for the system ad
ministrator, there is coverage of deployment and security issues; for the developer,
the authors address the deep details of XML, SOAP, UDDI and WSDL as well as
VI Foreword
the detailed design decisions and styles that make for well-crafted service-oriented
systems.
This would have been enough, but Olaf, Mark and Stefan complete their cover
age of Web services by at houghtful discussion of what's to come in the form of
evolving standards, Grid computing and the semantic Web.
Web services represent the further maturation of architectures for the enter
prise; this book will serve you well in understanding how to craft such systems of
quality.
Grady Booch
Chief Scientist, IBM Rational
Dedications
Olaf: To my parents, Hubert and Erika Zimmennann - for a myriad more than the
obvious reasons. You are such wonderful people! This book really is fory ou.
Mark: To my fabulous wife Kirsty - with love. Thanks for all your patience, sup
port and proofreading! I couldn', have managed it without you. Ic an't wait to get
back to carefree, drunken evenings and weekends, although I guess Illat also
means housework and DIY!
Stefan: To my parents Evamaria a nd Tonius. Thanks a million for your help and
support throughout the years.
The team would also like to dedicalc this book to hte memory ofChrisloph Purck
hauer, who tragically passed away just before we went into print. A Senior Con
sulting IT Architect at IBM Software Group Germany, Christoph developed the
Web services architecture pattems that appear in the Architecture Perspective and
provided invaluable input for the Future Perspective. He was a great mentor, IT
architect role model and close friend, and will be sadly msised.
Preface
This is Perspectives 011 Web Sen'ices - Applying SOAP, WSDL lIlId UDDI to
Real-World Projects, Taking the roles that exist in development projects, this
book provides seven views on solutions exploiting SOAP, WSDL, UDDI and sev
eral other Web services technologies (that did not fil into the subtitle).
Before doing so, let us spend a few thoughts o n the motivation for the book, our
goals and non-goals and you - the readership of the book we anticipate. Let us
also introduce the book structure and some notational conventions.
Motivation for this Book
The Web services trend is obvious and ubiquitously featured - there are numerous
articles, books and conferences on the subject.
The first wave of enterprise-scale applicalions and projects leveraging the bene
fits of the technology is on its way. However, there still is a lack of experience in
the field. Technical decision makers are struggling: what elements of the technol
ogy to apply and how to do so. This is av ariation oft he well-known "chicken and
egg" problem: no project without an architectural decision, no architectural deci
sion without experience, no experience without a project. Our book provides guid
ance and closes the gap we perceive between vision and reality.
The book is more than a absic introduction to Web services concepts; it targets
project practitioners and their everyday problems. For example, we attempt to
provide tangible artifacts such as qualification checklists to assist with the deci
sion as to whether Web services are an appropriate solution for a given business
scenario. Many illustrations simplify the nuderstanding of the topics at hand.
Sample project deliverables including source code demonstrate the concepts we
introduce.
Mission Statement
The goal of Perspectives 01/ Web Sen'ices is to enable project teams to rapidly ex
ploitthe benefits of the emerging Web services technology. In particular, we cre
ate awareness for opportunities, enable the reader to take conscious decisions and
jumpstart development work. Pointing out pitfalls to avoid, we create a safety net
X Preface
for first-of-a-kind projects. The experienced reader benefits from the thought ex
change that our best practices sections initiate.
Who Should Read this Book?
Our main target audience is technical decision makers and statT in satte-of-the-art
Web development projects. Due to a role-based approach, the audience not only
includes IT architects and developers, but also project managers and system ad
ministrators. The book will enable members of these professions to take architec
tural decisions regarding Web services more consciously and to accelerate the im
plementation of Web services-based solutions.
The book also is of interest to researchers, teachers and students of general soft
ware engineering and application integration courses.
The Perspectives Metaphor
Our approach to structuring the book is to make use of a metaphor also used by
IBM WebSphere Studio development tools and several software engineering
methodologies: each chapter provides one Perspecti)le, viewing the subject matter
from a different angle, which allows the different members of our target audience
to easily navigate through the book. I
For example, there is an Architecture Perspective aiming at the technical deci
sion makers on the project. Programmers will work mainly w ith the De)lelopment
Perspective; project managers will focus on the BII.rilless and the Ellgagement Per
spective. The Operatiollal Perspective mainly targets system administrators.
Each chapter starts with a quotation from one or more fictitious members of the
target readership - IT architect, project manager and so on - giving their opinion
about Web services and their expectations for the chapter.
Non-Goals
This book is not a full-blown XML introduction -there are numerous good books
on XML on the bookshelves already. We also assume that the reader has a basic
understanding of our Web services implementation paltform Java 2 Enterprise
Edition (J2EE), as we do not introduce J2EE concepts s uch ass ervlet program
ming and Enterprise JavaBeans (EJBs).
I As a side eifeet, the Perspective approach quite creates elegant cross references. For ex
ample, "in the Operational Perspective, we will show how to configure HlTPS as the
transpon prOTocol for SOAP".
Preface XI
Furthennore, it is not anb joective of theb ook to provide a classroom-style in
troduction to all underlying standards.2 For example, a very comprehensive intro
duction to the technology is Buildillg Web Services with Java by Steve Graham et
al. [49].
Our book is not a product marketing effort either. As already said, we tackle the
topic at hand in a practitioner-oriented, project-driven way.
The Development Perspective and most sections in the Operational Perspective
are Java and IBM WebSphere-specific. All other chapters are useful for people
with other backgrounds as well. For example, when implementing Web services
solutions with a platfonn such as .NET rather than 12EE, the same architectural
decisions have to be taken.
Approach
We hope that this book provides everything a project etam needs to know about
the development and deployment of Web services. The book documents our own
practical experience as well as consolidated information on product capabilities.
We use the IBM WebSphere Version 5 product family as our sample implementa
tion platfoml (most content is aslo useful if your platfonn is different).
The book adopts the tenninoIogy established by standards bodies such as the
World Wide Web ConSO/1il/1II (W3C), Organizatioll for the Advancement of Stmc·
tured ll1formation Standards (OASIS) and vendors such as IBM and Microsoft.
For example, we use an up-to-date definition of the tenn Web sen1ice, covering
HlTP and XML plus XML messaging via SOAP, the service description language
WSDL and two types of service discovery agencies, UDDI and WSIL.;
A real-world project approach proven to be successful is employed, covering
the entire development process from requirements engineering to development,
deployment and going live. We feature the lessons we learned and best practices
we harvested when implementing Web services solutions for our customers. Fur
thennore, we give you the opportunity to build, deploy and test a complete Web
services solution while exploring the technology.
We hope that due to this project-centric approach, you can also use the book as
a reference as you progress through your first own Web services development pro
ject. As we will see shortly, the book chapler structure matches with common pro
ject phases.
Throughout the book, we work with an integrated case study originating from
an insurance industry scenario. A fictilious insurance company called Premier·
Ql/otes Group, which fonned after the merger of PremierQuotes Illc. and Dirt·
Chetlp Illsurance, develops a set of mid-office applications using Web services.
We will watch the PremierQuotes application owners and the development team
as they construct their solution.
2 Emphasis here is on all, as our second chapter is aT mining Perspective.
J Ycs, wc will define thcsc acronyms vel)' shortly.
Xli Preface
Note: All our company and person names used in the case study are ficti
tious. To the best of our knowledge, none of them exist in the real world.
Outline to the Book Structure
When structuring the book, we decided to follow the same path projects take:4
• The Business Perspective deals with opportunity identification and analysis.
• The Training Perspective provides technical base education.
• The Architecture Perspective lays the conceptual foundation for solutions.
• The Development Perspective is a hands-on chapter implementing Web ser
vices and clients invoking them.
• The Operational Perspective investigates the physical view on Web services
solutions; it features both conceptual and hands-on sections.
• The Engagement Perspective takes a rear veiw on Web services projects.
• The Future Perspective gives an outlook to emerging technology.
In Chapter I, the Business Perspective, we talk aboUi the general advantages of
Web services and their main usage scenarios, as well as potential inhibitors and
what you can do about them. Both the authors and the anticipated readership of
this book are technical people; the business aspects are therefore mainly viewed
from this angle.~ However, we give pointers to truly business-oriented introduc
tions to Web services at the end of the chapter.
Chapter 2, the Training Perspective, introduces the base concepts underlying
any service-oriented architecture: XML including XML namespaces and XML
.~chellla, SOAP (not an acronym nowadays) and the Web Services Description
umguage (WSDL). The optional discovery technologies Universal Description.
Discovel)' and IlIIegmtioll (UDDI) and Web Services Inspection ulIIguage (WSIL)
are also featured.
The Architecture Perspective, our Chapter 3, first introduces the technical bene
fits of Web services, the W3C Web Service Architecture and Web services pat
terns. It also defines the architectural decisions to be taken in Web services pro
jects. Performance, scalability and security considerations are among the non
functional requirements that are discussed next. We also elaborate on current gaps
and countenneasures regarding Web services. We conclude with a collection of
Frequently Asked Questions (F AQs) about Web services (and our answers to
them).
In Chapter 4, the Development Perspective, we get down to earth and imple
ment a full blown J2EE enterprise application integration scenario involving two
4 At least projects employing a project and design methodology do.
sEven if technology is the main focus of this book, we do care about the value proposition
of Web services. Consequently, our Business Perspective intends to enaDle you to adver
tise Web scrvices solutions to prospective project sponsors.
