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Chapter 9. JSF front-end scenario 243

can even accelerate the implementation through the use of tooling. Rational

Software Architect for instance, supports an extensive library of commonly

used patterns, which can be easily applied to design models, and even

automatically generate code.

򐂰 Design should favor industry-standard technology.

It is often tempting to use unproven, or vendor-specific technology. For

instance, a particular vendor might offer a proprietary package that perfectly

fits the customer requirements. This solution might very well be cheaper and

faster to purchase. There might also be a new open source framework, which

appears to address many of our design goals.

There are times when taking either of these approaches is a valid option, but

the risks need to be well understood. Proprietary packages will generally limit

the flexibility of your environment to change, because you will be dependent

on the availability of new versions from the provider. New technology might

sound appealing, but without careful analysis you can find yourself in the

proverbial

bleeding edge. New technology tends to evolve. Applications

written using early versions can quickly become deprecated. In either

scenario, staffing becomes an issue as well, because it might be difficult to

quickly attain resources familiar with new or vendor-specific technologies.

Therefore, all things being the same (not always an easy determination), we

recommend the use of established industry-standard technology.

For the ITSOMart front-end application in particular, there is no need of any

new or specialized technology. Therefore, our design approach should rely on

industry standard, preferably open standards, technology.

9.2.2 Component model

Now that we have discussed the various principles guiding our design process,

we will discuss the different aspects of the design approach we selected. The

component model will describe the overall structure of our application, in terms of

its high level components.

Component diagram

The component diagram in Figure 9-2 on page 244 depicts the different software

components which make up the front-end of the ITSOMart application. The

following sections elaborate on the different components.

244 Patterns: Implementing Self-Service in an SOA Environment

Figure 9-2 ITSOMart front-end component model

Model-View-Controller architectural pattern

Our component model is based on the Model-View-Controller (MVC)

architectural pattern, widely used in user interface applications for many years. It

is particularly well-suited for Web-based applications, making it an overwhelming

choice across the industry. 7.2.1, “Model-View-Controller design pattern” on

page 141, discusses the MVC pattern in detail, therefore we do not repeat it

here. We simply review the main points so we can show how it is realized in the

ITSOMart application. The MVC pattern divides the application in three

components, indicated by differently shaded areas in Figure 9-2:

򐂰 The Model represents the data of the application, as well as the business

rules and logic that govern the processing of the data. In the ITSOMart

front-end, the Model is implemented through EJB classes that interact with

the database and back-end.

򐂰 The View is a visual representation of the model. Multiple Views can exist

simultaneously for the same Model. In the ITSOMart application, the View is

implemented using JSF and JSP Web pages.