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ColdFusion: Article

An Online Ticket Store

An Online Ticket Store

In the January issue of CFDJ we walked through the development of the online "storefront." As a software architect, when designing an enterprise-level application, you frequently have to justify the choices you make in the technologies you select for the solution. You often end up answering a trio of questions — "why?", "what?" and "how?"

This month, accordingly, I'd like to step back from the development of the Online Store application (the "what?" and the "how?") and focus on the "why?" Several readers have asked why using CF template pages with Java servlets is such a good idea. The whole application could have been built using just the CF application server. Similarly, the application could have been built using just Java technologies. These are valid questions. Coincidentally, I've been asked the same questions at my place of work. With the advent of J2EE (Java 2 Enterprise Edition) and the emergence of Java Servlets/JavaServer Pages (JSPs), why would Web developers look at a CF application server and use a "proprietary" markup language for creating business applications? If your company commits to a J2EE architecture, where does CF fit?

Does it fit?

Seventh in a series of articles focused on using ColdFusion and Java technologies to develop a Ticket Store application. The first article in this series was published in the July/August 1999 issue of CFDJ (Vol. 1, issue 4), and the next four were published in Java Developer's Journal. The sixth installment appeared in January CFDJ (Vol. 2, issue 1).

But First: Why an Online Ticket Store?
Before discussing the application, I'd like to take a moment to mention how the idea for the application originated. Last year, I worked on a project that involved setting up a product configuration site for some of our core engines. The functionality of these core engines was accessible via a Java API. One alternative for creating the site was to use Java's client-side technologies, that is, applets and Swing components, for creating the browser clients, but there were some problems with this approach. One of the main ones was that, although the functionality could be accessed from a Java/HTML client through a browser, we didn't have any Web developers who could develop the site in Java. Our computer graphics and media groups were more versed in Allaire's CF, and therefore better suited for creating the site than Java developers from disparate Java groups. After all, that's really part of their job description — but it's not part of the job description for Java developers.

CF allowed us to create the "storefront." The user preferences and accounts were maintained in a database directly accessible via CF tags. All the graphics and interactions for the user interface were handled in CF and JavaScript. For highly interactive pages we leveraged Java applets. However, there was the dilemma of making HTML data available from the Java engines to the CF pages. Java servlets offer the ideal mechanism for serving up HTML to the client. At that time (February 1999), however, there was no published way to access servlets from a CF page. So my colleague and I created a simple string-based protocol to exchange data from a CF page and a Java servlet by passing the parameters on a URL command line.

As a part of the application, I developed a custom tag for CF allowing us to access servlets from ColdFusion. I wanted to demonstrate how CF and Java technologies could cooperate to create a distributed application, and I wanted to use an example business that would span all the tiers of a distributed application. Hence, the Online Ticket Store was born.

Supplementary Technologies
CF and Java offer supplementary technologies. There's definitely an overlap in some of the functionality, but if the design is chosen carefully, application developers can benefit from the features offered by both Java and CF environments. The CF application server allows a developer to create virtual online storefronts and sites. Java has technologies that cover the entire span of a distributed application, from the user interface to back-end adapters that extract the data from legacy engines. However, creating sophisticated template-based user interfaces and Web sites is not Java's forte. The computer industry has a large segment of developers who are involved in rapid application development of Web-based systems, but they're not necessarily programmers since they don't program using traditional languages such as C++ and Java. Their skills are more suited to Web development using scripting languages.

At the same time, in an enterprise-wide application, there's a need for programmers who can create the business logic for these applications and serve it up to the client. They're traditional programmers who program in traditional programming languages.

The Broad Acceptance of HTML UIs
Over the past few years, Java made a bid as a language and platform that can be used to develop enterprise-level distributed applications. While it has grabbed a large part of the territory on the middle tier and the server side, HTML-based clients have clearly won the Internet war. Most of the applications are moving toward pure HTML user interfaces for Web applications. Chances are your customer will require a browser-based interface in addition to other types of clients. Java applets are suitable for some GUI components, but they're not appropriate for developing the entire client. Java servlets, on the other hand, are used to serving up HTML to the browser client from the server. JavaServer Pages are similar to Active Server Pages (hence the name JSPs) and allow developers to embed programming code inside HTML pages. CFML allows the embedding of ColdFusion tags to make server-side calls. The purpose of these mechanisms is the same — to serve up HTML to the client.

Middleware Access
In order to access server-side business objects, the middleware components of a distributed architecture need to support access protocols for the popular object models — COM, EJB, CORBA and Java objects. In the Java world this access is provided through Java servlets and JSPs. JSPs exist in the form of embedded Java code in the HTML page. JSPs are compiled into servlets the first time they're invoked and thereafter function as normal servlets. The advantage of JSPs is the same as that of ASPs. They can be used by Web developers to create Web presentation components such as shopping carts.

CF allows access to server-side components directly via the WDDX serialization mechanism. These components may be based on Java, COM or CORBA object models. Servlets enable access to Java server components, which may be Java Objects or Enterprise JavaBeans.

Presentation Vs Business Components
Middleware components may be divided into two broad categories — presentation and business logic. The presentation components are responsible for generating data for the client. Business logic components are responsible for extracting data from the back-office applications. Decoupling business logic components from presentation components has several advantages — reusability, scalability, simplicity of design and so on. Tools such as CF are more suited to building presentation components. Technologies such as Java servlets and JSPs are better for building client-side components. Their combination enables a more robust, scalable and manageable application.

The crux of the J2EE platform is the EJB model. EJBs are business logic components that execute in a Java application server. Servlets and JSPs are a means of accessing EJBs from the Web. Therefore, CF tags can create the presentation components that "execute" in the CF application server. These components can access business logic in the form of Java or EJB objects via servlets. The business logic components can provide access to the back-office applications.

I'd like to list some reasons why CF and Java technologies make a good combination:

  • From a project management and development point of view, the team that builds the storefront for your application typically consists of people who understand Web development and graphics, but not necessarily Java. Once you have standard templates in JSPs that allow you to access server-side components through plain scripting, maybe you won't need the decoupling. However, my experience has been that the guys writing Java code for the Web development team usually don't understand the issues of Web site and storefront development very well.
  • CF allows you to abstract the access mechanism to the objects on the server side. JSPs mean that you are tied to Java. If you want an abstraction layer that allows you to get to other technologies — for example, COM on the server side — CF is a good tool to build that abstraction layer.
  • Some components, such as a payment module that's hooked to a credit card service, don't need to connect to the server side and can be handled at the Web front. CF allows easy integration with such systems.
  • CF can be used for rapid prototyping. Since it allows access to different data sources via scripting, you can build up a site without a huge amount of investment.
  • Due to the hooks into LDAP and so on, you can build a level of role-based personalization using CF.

More Stories By Ajit Sagar

Ajit Sagar is Associate VP, Digital Transformation Practice at Infosys Limited. A seasoned IT executive with 20+ years experience across various facts of the industry including consulting, business development, architecture and design he is architecture consulting and delivery lead for Infosys's Digital Transformation practice. He was also the Founding Editor of XML Journal and Chief Editor of Java Developer's Journal.

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