Web Services Development

A bevy of new features meet app development trends head-on

There are many other new features in the IDE, a few of which I can list briefly:

• Object Tree View is a new window (pane) in the IDE that lets you traverse the active objects in a form. (See Figure 1.)
• A Diagram window used to graphically design database relationships for Data Modules exploits 'two-way' coding, which lets you edit code directly or use components. The compiler will reconcile the changes without overwriting any code.
• Forms can now be inheritable objects; for example, you can create a "utility form" and reuse it with all properties and methods in many different instances.
• The ActionManager has been enhanced as the centralized location to handle common user interface actions such as Open, Save As, Print Setup, and Run. This is a convenient way to organize and customize these often-used functions.
• XML Tree is used to parse and validate XML documents within the Code Editor. This and other tools, such as the XML Mapper and low-level compiler support, provide Delphi with excellent native support of XML.

The Delphi approach is to provide the programmer with a shell or skeleton of an application as quickly as possible. You attach relevant components to this shell and then modify properties and add code to make a working program. The Delphi system was designed to be supremely flexible so that a developer can feel just as comfortable creating a DLL, a distributed object, an application form, or a Web service.

This brings me to the heart of the new material in Delphi 6 focused on Web services: WebSnap, BizSnap, and DataSnap. The "snap" part means nothing more than being able to quickly put something together; but in Delphi these names put a programming face on the concept of Web services. I spent considerable time learning and testing the new features, and while I won't say I'm a complete convert to Web services, the Delphi tools go a long way toward demonstrating how they can be built and used.

The Snaps

DataSnap handles what might be called "crossroads" functionality in the middle tier between database servers and client applications. Its main job is to make stateless connections with data from different sources and using different protocols such as DCOM and CORBA. The connections can be made in a number of ways: direct drivers, Microsoft ADO, or Borland Database Engine. Data from the connections is stored in a local (server or client) DataSet. Between the connection and the DataSet, the developer has considerable control over data validation and application of business rules. What makes this "Web services enabled" is the thorough use of XML as the data intermediary, and SOAP as the framework. While the database management part of DataSnap should feel familiar to most developers, using it in the context of SOAP presents an interesting learning curve.

WebSnap is a kind of application development platform for Web services and applications that use Web servers (ISAPI, NSAPI, Apache, and most CGI-based servers). In effect, it is to HTML and DHTML pages what DataSnap is to databases, a kind of crossroads where different scripting (such as JavaScript and VBScript) and HTML can be hooked together within a Delphi application. It does this by providing a specialized form, a WebModule, to contain components and WebActions to organize common Web methods. Delphi provides a sophisticated WebSnap Wizard to produce a server program for all major Web servers. This system is a huge improvement over the patchwork process normally involved with developing this kind of application, and the natively compiled programs it produces are blazingly fast.

At a high component level, BizSnap is a development platform for business Web services, especially for B2B and B2C applications. It uses XML as the translator medium between local and business partner data and provides some excellent parsing and mapping tools to do this. BizSnap uses SOAP to moderate the interaction between applications. Using SOAP objects, it's relatively easy to develop services for many kinds of business transactions. In some ways, BizSnap will be a replacement for COM- and CORBA-based applications, although Borland is aiming at coexistence with these older protocols - and the newer frameworks such as Microsoft .Net, Oracle .NOW, and Sun ONE.

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Taken together, the three new technology packages give a developer more than an adequate set of tools to explore and implement Web services, especially at the enterprise level in Web-based B2B business relations. This is a unique environment, and although you should expect it to evolve (even the standards it's based on are evolving), it gives Delphi a walloping head start in the Web services contest.

Delphi won't replace Java or C++ for enterprise-level programming. But it does fit neatly in the class of development systems for the ubiquitous data applications, utilities, and small programs so vital to business. It now covers Web applications and services within the same development system. In this realm, Delphi is a formidable competitor to Microsoft Visual Basic. For software developers and corporate IT shops, Delphi is a state-of-the-art system that is neither Microsoft nor Java. You can argue that it isn't mainstream. You can also argue that its "crossroads" stance has many advantages - especially among the rapidly evolving Web standards. Delphi 6 is Borland's proof that not only can it keep up, but also take the lead.

Nelson King (nelsonking@earthlink.net) has written nine books on database application programming and spends much of his time in the trenches of enterprise software development.