What is Application Server Software?
An Application Server provides services and infrastructure for developing, deploying, and running applications.
Application Server Software Features & Capabilities
Ease of download and installation
Support for a number of different programming environments or IDEs
Simultaneous support for multiple applications
Adequacy of documentation and user community vibrancy
Overall performance including deploy time, initialization time etc.
Compliance with open standards like Java EE and DSHi
Administration console for managing application and environment
Application servers are server programs in a computer in a distributed network that provide the business logic for an application program. As such they are the middle tier of a standard three-tier architecture.
In a three-tier client/server architecture, the application tier sits between the presentation tier and the data tier. The presentation tier displays information related to services available on a website. The backend data tier houses database servers where information is stored and retrieved. Data in this tier is kept independent of application servers or business logic.
In other words, when there is a request from the client, the application server process the business logic and makes a call to the database to retrieve the relevant data.
Application Server vs. Web Application Server
An application server is distinct from but often works in conjunction with, a web application server. A web server can only handle HTTP requests, while an application server can serve business logic via many different protocols. In a standard setup, the web server receives a request from the GUI or front end and then sends that request to the application server for business logic processing before it is sent back to the web application server and then back to the user via a modified web form.
In addition to processing application business logic, application servers have another function. They often simplify the building of client applications by providing the building blocks that help create the applications themselves. The best-known example is Java Beans in the J2EE environment. Indeed, application servers are closely associated with the J2EE standard. J2EE is an enterprise level Java application development platform.
Some applications like Apache Tomcat are open source. Commercial enterprise-level application server platforms are on-prem licensed software, and pricing starts at around $7,000.