JAVA: JavaServer Faces

<< JAVA: Client Side Validation & JavaServer Faces (JSF)

Web Design & Development CS506

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

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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