Definitions: Application Servers

Definition

An application server is a software module within a distributed network that contains the APIs and business logic needed by standard applications. The application server is usually considered one of the three legs of a typical business application, the other two being the graphical user interface (GUI) and the database/transaction server.

Most application servers are based on the J2EE or Java EE 5 formats,  including a number of WebSphere releases from BEA, and other from Red Hat, Oracle, Sun and SAP.

Business Applications

Any number of functions can be relegated to the application server, with the goal being to improve network performance by relegating application traffic to its own tier. Common uses include logic centralization to facilitate configuration changes and updates, as well as security enhancement by focusing on only one point of data access and application management.

An application server can also be used with a Web server that supports a browser-like interface to simplify the transfer of data to and from the app server.

Deployment Concerns

Supporters believe the use of an application server enhances collaboration among developers and improves the application development process, saving money in the long run. Establishing a smooth-running environment can be tricky at  times, though, considering all software written for the application must integrate with the server environment, and all data is distributed back out must contain client code. These problems are not overwhelming, but they do point up to some of the challenges involved with network collaboration.

Another problem is the lack of integration between Java- and non-Java-based servers. This increases the complexity of many application  integration platforms like Business API and Web Services Interoperability in order to accommodate the different formats.

Technical details

The inner workings of application servers vary widely, as each developer has been largely free to set their own definitions. Some are open source systems, like JOnAS and Base4, while others conform to leading enterprise platforms, such as the Java Enterprise Specification.

Microsoft has established its own platform called the .NET Framework. It  incorporates a number of Microsoft modules like the Windows Communication Foundation and Internet Information Services.