Over the past year, Web application servers and other middle-tier products have evolved from new kids on the block to just more familiar faces. Application servers, the products that handle the business-logic layer in a three-tier environment, are well-established in the market and in many enterprise IT shops.

Back to Basics

Enterprise-ready Web application servers usually offer robust system-level services, such as application load-balancing across multiple hosts and automatic failover, which generally includes session and transaction preservation and rollback so that users won't lose their sessions or data in the middle of a online transaction.

Web application servers also manage back-end data-source connectivity, often boosting performance with database connection pooling and caching. They also handle front-end connectivity to the user interface layer directly via an integrated Web server or by interfacing with an external Web server. They may handle transaction processing directly or via third-party products, such as BEA Systems' Tuxedo or IBM Corp.'s Encina/CICS.

A middle-tier application server centralizes your business logic and increases manageability, scalability and fault-tolerance. For additional information, see "The Basics of N-Tier Architecture," at www.networkcomputing.com/922/922buyerside1.html#sb1; for a more general look at Web middleware, go to www.networkcomputing.com/922/922buyers2.html.

All Grown Up

It's a commonly held belief that a technology area is maturing when the big players jump in and the number of mergers and consolidations is as large as the number of startups. If that view is accurate, then the Web application server market is well on its way to maturity. New players in the market keep cropping up but the merger frenzy has begun with major vendors eyeing existing players as if they were hors d'oeuvres. In the biggest merger, NetDynamics and Forte Software were both gobbled up by Sun Microsystems, which then collaborated with Netscape Communications Corp. to release the new iPlanet application server as a descendant of both Netscape's Application Server and Sun's NetDynamics. Expect further consolidation this year, and account for it when evaluating products for strategic deployment.

The market has also shown an overall increase in product capability with the smaller, less capable products evolving into major players. Former "lightweight" or small-to-medium enterprise-only products, such as Pervasive Software's Tango and Allaire Corp.'s ColdFusion, are leaping onto the list of products with solid enterprise-level features. They hold their own alongside the perpetual heavy hitters, namely Apple Computer's WebObjects and Bluestone Software's Sapphire/Web.

Many of the features that once differentiated these products, such as load-balancing, failover and database connection pooling, have become increasingly commoditized. Although some degree of difference still exists between the products, it's primarily in the depth, flexibility, granularity/control and administration of these features, rather than in their presence or absence. Further, many vendors are trying to carve out niches to differentiate their products.

One such vendor is Forte, whose Business Application Server has an abstraction layer for business logic that could, in many cases, let business managers modify business rules without having a programmer change any code. Now that it owns Forte, Sun plans to leverage this capability in its products. Other products are being refocused as e-business providers in the hopes that they'll ride that wave of market interest.

Another key differentiator is Java support. Virtually all Web application servers support Java standards to some degree, but a significant number of these products go a good deal further; some, such as BEA's WebLogic, are designed primarily around Java. Complete and current support for servlets, EJB (Enterprise JavaBeans) and all the components of the J2EE (Java2 Enterprise Edition) specification are important factors here. For more information, see "Spilling the Beans on Java Application Servers" at www.networkcomputing.com/1022/1022f2.html.

Major vendors are leveraging their development muscle, as well as brand identity, marketing prowess and strategic partnerships, to position themselves at the top. IBM's WebSphere initially started way behind the curve established by smaller competitors, such as SilverStream, Apple and Bluestone.

The original WebSphere offering was somewhat half-baked (see "In the Middle: Enterprise-Ready Web App Servers," at www.networkcomputing.com/1011/1011 r1.html for a head-to-head review of eight Web application servers), but its most recent release, WebSphere version 3, is a much more complete, capable and polished product.

Creature Features

What cutting-edge features should you look for in a Web application server? And which current and upcoming technologies should it support? Here are a few key features you shouldn't live without. First, you'll need XML support, both for XML data parsing and XML output. During the next year, expect XML use to take off, especially in e-commerce applications. Ask prospective vendors what their strategic visions are for XML in their products: Many companies, including Bluestone and BEA, are greatly endeavoring to make the use of XML a core capability of their Web application servers.

Next, check for the depth of functionality for key system-level services, such as failover and load-balancing. Find out how granular your load-balancing control will be and what algorithms will be available. Is it a simple "round-robin" or "next-available" system? Or are more flexible balancing options offered based on measured host load, relative capacity and other factors? If a host fails during a transaction, will the failover routine allow for maintenance of users' session data, or will users lose the data they were entering or accessing? Fault-tolerant session persistence is essential for storefront e-commerce applications.

If you're considering a Web application server with an IDE (integrated development environment), make sure it's well-integrated into the overall package. You'll want to know if there's a genuine IDE or if the vendor simply tacks on a third-party development tool. Ask the vendor the following questions: Does the IDE support integrated source-code control or other team collaboration features? How complete are the debugging and code-development features? Can you do cross-component debugging? What kind of RAD (rapid application development) tools are included or integrated to help developers go from high-level design to final code? You may want your application server to include an integrated Web site development tool, but integration may be provided only with a third-party tool. Get the facts straight because the tighter you can tie together the many elements of your n-tier system, from content generation to deployment to maintenance, the fewer management nightmares you'll encounter along the way.

Finally, make sure your Web application server has a commitment to a distributed component model, such as EJB, CORBA or DCOM/COM+. EJB support is almost universal, but if you're a hard-core Microsoft shop, you may want to use DCOM/COM+. And if you have an installed base of systems using CORBA, make sure you can interoperate with them easily.

Can You Manage?

Management capabilities are always essential, though they're also one of the hardest features to evaluate quantitatively. You'll need to know how easy or difficult it is to deploy, monitor and maintain large, complex enterprise systems with your considered products. Find out if there are automated deployment and site replication tools, what kind of tools are included for performance monitoring and how security and access control are handled.

If you're using your Web application server for e-commerce systems, closely examine the built-in capabilities for back-end connectivity and integration with ERP (enterprise resource planning) and other line-of-business systems. The more customized development you'll need in order to use existing and legacy systems, the more money you'll have to spend on coding and maintenance.

It's also important to gauge the availability of cross-platform support. As your business and IT systems grow, you may want to migrate your applications and portions of your architecture to alternate platforms. You'll also benefit from increased flexibility if your Web application server can make use of a variety of Web servers.

DIAGRAM: Application Server Architecture

~~~~~~~~

By Richard Hoffman

Send your comments on this article to Richard Hoffman at rhoffman@nwc.com.

 

Almost any Web application server will support one or more of the standard models for accessing distributed components. As it becomes increasingly feasible to mix and match "componentized" code across platforms and operating systems, this capability will be crucial to many IT implementation strategies. Here are the three dominant models you should brush up on: CORBA (Common Object Request Broker Architecture): CORBA is the oldest, most mature and most widely implemented distributed object technology. Individual vendor implementations are based on a specification distributed by the Object Management Group, an industry consortium. The latest specification, version 3.0, is due out shortly, but it's still questionable as to which portions of the specification will be actively supported by vendors.

 

COM/DCOM/COM+ (Component Object Model, Distributed COM): Microsoft Corp.'s component model is widely implemented in Windows 95/98 and NT. Introduced in 1996, DCOM has been relabeled COM+ in the Windows 2000 product line. Along with other Microsoft products-such as Microsoft Transaction Server (MTS), which is integrated into the operating system in COM+, and Microsoft Message Queue (MSMQ)-it's a relatively easy-to-implement, largely Windows-only component model.

 

EJB (Enterprise JavaBeans): EJB's recent 1.1 specification release incorporates many eagerly awaited features, such as container-managed persistence for entity beans. Along with other Java technologies-such as JNDI (Java Naming & Directory Interface), JTS/JTA (Java Transaction Service/Transaction API), JMS (Java Messaging Service), Java IDL (Interface Definition Language) and JDBC (Java Database Connectivity)-EJB 1.1, in theory, offers a robust standards-based method for deploying distributed cross-platform components throughout the enterprise.

 

For more details on all three, see "Sneaking Up on CORBA: The Race for the Ideal Distributed Object Model," at www.networkcomputing.com/1009/1009f2.html.