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Web Design and Development

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Web Design & Development ­ CS506
VU
Lesson 45
JavaServer Faces
In the last lecture, we have covered the basic nutshells of JSF. Having a belief on "learning by doing", in
this lecture another example is also given to show you the capabilities of JSF.
Example Code: Addition of Two Numbers
The example code ("AddNumbers") is given along with the handout. It is strongly advised that you must
see the lecture video in order to learn the making plus working of this example.
This example demonstrates the usage of value and method binding expressions, managed beans, and how
to use page navigation technique using IDE etc.
Web Services
In the remaining handout, we'll take an overview of web services' potential, their types and working
model. Resources are given at the end for those who are interested in learning new technologies.
Introduction
Web services are Web-based enterprise applications that use open, XML-based standards and transport
protocols to exchange data with calling clients.
Web Service is becoming one of those overly overloaded buzzwords these days. Due to their increasing
popularity, Java platform Enterprise Edition (J2EE) provides the APIs and tools you need to create and
deploy interoperable web services and clients.
Web service, Definition by W3C
W3C recently has come up with a decent definition of web services. According to W3C, "A Web service is
a software application identified by a URI, whose interfaces and binding are capable of being defined,
described and discovered by XML artifacts and supports direct interactions with other software applications
using XML based messages via internet-based protocols".
Distributed Computing Evolution
Let's think a little bit on how distributed computing technology has evolved.
In the beginning, things were built and deployed typically in the form of client and server model in which
clients talk to a single server, for example, remote procedure calls (RPC).
The second phase can be called web-based computing in which many clients talk to many servers through
the net. In this phase, communicating partners still have to go through some pre-arrangement in terms of
what common object model they have to use or what common communication protocol they have to agree
upon.
Finally, the web services model in which service users and service providers can be dynamically connected.
And the pretty much every computing device and application participates as both service user and service
provider.
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Web Design & Development ­ CS506
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Characteristics of Web services
Web services are XML-based throughout. Pretty much everything in the domain of Web services is defined
in XML. For example, the format of the data being exchanged between service user and service provider is
defined in XML or the description of web service is defined in XML.
Because the only contract that has to be agreed upon between service user and service provider is syntax
and semantics of XML messages, as long as valid messages can be generated and understood, it does
not matter what programming language is used. So a web service is said to be programming language
independent.
Web services can be dynamically located and invoked. And typically they will be accessed and
invoked over both internet and intranet.
Interoperable
Connect across heterogeneous networks using ubiquitous web-based standards
Economical
Recycle components, no installation and tight integration of software
Automatic
No human intervention required even for highly complex transactions
Accessible
Legacy assets & internal apps are exposed and accessible on the web
Available
Services on any device, anywhere, anytime
Scalable
No limits on scope of applications and amount of heterogeneous applications
Types of Web service
Data providers
For example, a service providing stock quotes
Business-to-business process integration
For example, purchase orders
Enterprise application integration
Different applications work together simply by adding a webservice wrapper
Comparison between Web page & Web service
Just to give you a sense on the difference between a web page and a web service, consider the
following table:
Web page
Web Service
Has a UI
No GUI
Interacts with user
Interacts with application
Works with web browser client
Works with any type of client
Web service Architectural Components
Following are the core building blocks of web service architecture.
Service Description ­ how do clients know how it works (which functions, parameters etc.)?
At the minimum, you need a standard way of describing a web service that is universally
understood by all potential service users and service providers. This is important because without
commonly agreed upon description of service, a service provider might have to  produce individually
tailored way of describing its service to all its potential service users.
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Web Design & Development ­ CS506
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