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 The following topics describe the application server evolution, its place in SOA with an introduction to the WSO2 Application Server.

Table of Contents

What is an Application Server

An Application Server (AS) is a software program which accommodates the hosting, deployment and management of various applications. Residing in the middle tier, between an organization’s database layer and the user-interaction layer, an application sever facilitates communication and connection of the front and back tiers.


In addition to business logic implementation, application servers also centrally manage most reusable operations like security, monitoring, governance, high-availability etc. Separation and central management of an organization’s pool of applications and services are key reasons for the wide acceptance and adoption of application servers in distributed enterprise architectures today.

Evolution of Application Servers

The application server concept emerged in early client-server environments. The term was originally used to differentiate servers that hosted databases and related services from file/print servers.


Application server functionality has enormously expanded over the years. Nowadays, most enterprises have 3-tiered (or N-tiered) distributed architectures with Web-enabled applications and services hosted and managed in application servers.

The WSO2 Application Server

The WSO2 Application Server is a lean, open source, high-performant application server with Web application and Web services deployment and management capabilities.


WSO2 has positioned the application server product in 3 different phases. Currently in use is the WSO2 Application Server, which is the successor of WSO2 Web Services Application Server (WSAS). WSO2 WSAS was launched in 2008 with its predecessor being WSO2 Tungsten.

The WSO2 Application Server in context of SOA

An enterprise’s application servers are typically accessed by a variety of heterogeneous clients, within a LAN and over the Internet. Modern-day enterprises acknowledge the advantages of building Web-enabled applications on Web service interfaces. Web services have also become the fundamental building block of a service oriented architecture (SOA) implementation.