Web Application Servers

Allaire ColdFusion
Allaire Corporation
Web Site: http://www.allaire.com/products/coldfusion
Allaire's ColdFusion is a feature-rich application server that uses HTML-like syntax to mark up pages to provide dynamic content. The Cold Fusion Markup Language, or CFM, is a large set of such tags, covering everything from typical programming constructs, such as variables, conditional statements, and loops, to database access, COM/DCOM object access, and (with ColdFusion 4.5), the ability to access Java Servlets and Enterprise Java Beans through Allaire's JRun Java Application Server (see below). A scripting language, CFScript, provides a complete set of functions libraries for a wide variety of uses like mathematical operations, string manipulation, and more. You can also develop your own custom tags, allowing you to develop reusable "templates" with CFM. Support for a variety of methods for maintaining user session state and user authentication is also provided. ColdFusion Studio, while not available for Linux, is a top-notch IDE for ColdFusion developers.

Active Server Pages Active (ASP)
Server Pages allows you to embed blocks of code written in VBScript, JavaScript, or even PerlScript, into your HTML pages. There are two companies of note offering implementations of Microsoft's ASP environment for Linux (and other UNIX operating systems).

Chili!Soft ASP
Chili!Soft, Inc.
Web Site: http://www.chilisoft.com
This award winning port of Microsoft's ASP environment offers the capability to script dynamic Web applications using JavaScript or VBScript to interact with COM objects and relational databases, provide session state management, and more. Developers familiar with ASP on Windows platforms will be comfortable moving their code to Chili!Soft ASP.

Halcyon's Instant ASP
Halcyon Software
Web Site: http://www.halcyonsoft.com
This implementation of ASP is Java-based, making for a platform-independent product offering by Halcyon Software. This makes Instant ASP a viable ASP application server for any platform that supports Java 2. The Java implementation also makes integration with other Java code, like Java Beans, more viable.

PHP (PHP: Hypertext Preprocessor)
Web Site: http://www.php.net
PHP is another environment, like ASP, that embeds blocks of script into HTML pages. PHP is an Open Source solution, freely available for a wide variety of platforms, including Linux. This is a full-featured environment that has been available for years, and is in widespread use on the Web. If you're on a tight budget, PHP is a fine alternative for building dynamic data-driven Web sites.

Enterprise Application Servers

The bulk of what would typically be termed Enterprise Application Servers are all products that implement Sun's Java 2 Enterprise Edition (J2EE) specification. Tomcat, discussed in this article, is the reference implementation of the Java Servlet and JSP specifications, which are just one part of the overall Java 2 Enterprise Edition specification. Additional features within J2EE include support for Enterprise Java Beans (reusable components written in Java), JDBC for database connectivity, JNDI for directory services, and more. Visit http://java.sun.com to learn more about J2EE and the rest of the Java product offerings and specifications. While there are undoubtedly a number of features that distinguish the various products implementing J2EE-based application servers, I will not attempt to enumerate them here. Visit the Web sites of the companies below, all of whom have Linux versions of their products, to learn more.

IBM WebSphere
IBM
Web Site: http://www.ibm.com/websphere
IBM holds a large part of the market share for J2EE application servers. IBM also has an Interactive Development Environment (IDE), VisualAge for Java, that is well integrated with WebSphere. Unlike Allaire's IDE's for either ColdFusion or JRun, the Visual Age for Java IDE is available on Linux as well as Windows platforms.

BEA WebLogic
BEA Systems
Web Site: http://www.bea.com/products/weblogic
BEA WebLogic is probably IBM's primary competitor in this market, and on the surface appear to have very similar products. BEA lacks the tightly integrated IDE, but offers highly regarded products such as Tuxedo for transaction platform, and eLink for integrating Web applications with enterprise (i.e., legacy) backend systems.

Allaire JRun
Allaire Corporation
Web Site: http://www.allaire.com/products/jrun
Like IBM, a distinguishing factor for Allaire is their development environment, in this case JRun Studio. An interesting possibility with JRun, for sites using ColdFusion 4.5 or higher, is the ability to deploy Java Servlets and Enterprise Java Beans in JRun, and interact with them in your ColdFusion pages.

Secant Extreme Enterprise Server
Secant Technologies
Web Site: http://www.secant.com
Secant may not get quite the press of IBM or BEA, nevertheless, they appear to have a solid offering in the J2EE market that has won its own share of both customers and awards.