App server definition: Types, examples & web server differences

An app server, short for application server, is a software framework or platform that manages and deploys web applications and services. It acts as an intermediary between users and the back-end databases or resources, handling business logic, security and data access.

App servers play a crucial role in web application development and delivery by processing client requests and generating dynamic content.

App servers serve various purposes in web application development and deployment. Some common uses include:

1. Handling client requests - process incoming user requests and generate appropriate responses based on the application's logic and data
2. Managing business logic - execute the application's core logic, facilitating data manipulation and business rules implementation
3. Database access - interact with databases to retrieve and update data required by the application
4. Session management - maintain user sessions and state information to provide a personalised experience
5. Security enforcement - enforce security measures like authentication and authorisation to protect sensitive data and resources
6. Load balancing - distribute incoming requests among multiple servers to ensure optimal performance and scalability
7. Caching - cache frequently accessed data or resources to improve application performance and reduce database load
8. Integration with other services - enable communication with external services or APIs, allowing seamless integration with third-party functionalities
9. Handling transactions - ensure data integrity and consistency during complex operations
10. Web services deployment - They can host web services that enable communication and data exchange between different applications

A web server is a software that handles HTTP requests from clients (web browsers) and serves static content like HTML, images and files to display web pages.

An app server and a web server have different roles in web and mobile apps. The web server is like a bridge between the client (usually a web browser) and the web application.

The app server, on the other hand, executes the application's logic, processes data and generates dynamic content based on user input.

The app server works closely with a web server to deliver complete web applications to users. Together both of them make websites and web applications work smoothly.

There are several types of servers, each designed to cater to specific needs, key features and technology stacks. But broadly, there are three types:

1 - Active Servers

Active servers are a type of application server that actively execute server-side scripts and interact with databases and other resources to generate dynamic content in response to client requests. They handle business logic, process data and provide real-time responses to users.

2 - Web Information Servers

Web information servers are application servers specifically designed to handle requests related to web content and information retrieval. They process queries, manage databases and deliver dynamic web pages containing relevant information to users.

3 - Component Servers

Component servers, also known as component-based application servers, are designed to host and manage reusable software components. These components can be dynamically assembled and executed to provide specific functionalities for web applications, promoting modularity and code reusability.

There are many examples of app servers that cater to specific languages, frameworks or use cases. Listed below are some of the most commonly used:

1 - Java EE app servers

These app servers are designed to support Java Enterprise Edition applications, providing a range of Java-specific features and functionalities.

2 - .NET app servers

Specifically tailored for Microsoft's .NET framework, these servers facilitate the deployment and execution of .NET applications.

3 - PHP app servers

Geared towards hosting PHP-based applications, these servers are popular choices for websites and web applications developed using PHP.

4 - Node.js app servers

Node.js servers are optimised for running applications built on the Node.js runtime, well-suited for real-time and data-intensive applications.

5 - Python App Servers

These servers support hosting Python-based applications and are often used for web development with frameworks like Django or Flask.

6 - Ruby on Rails app servers

Optimised for Ruby on Rails applications, these servers simplify the deployment process for Ruby-based web apps.

7 - Apache Tomcat

This lightweight Java-based app server is commonly used for hosting Java servlets and JavaServer Pages (JSP).

8 - Microsoft Internet Information Services (IIS)

While not strictly an app server, IIS can function as one for .NET applications and other web technologies on Windows servers.

9 - WildFly (formerly JBoss):

An open-source Java EE application server designed for enterprise-level applications.

10 - Nginx

Although primarily known as a web server, Nginx can also function as an app server, especially for serving static content or acting as a reverse proxy server.

The choice of an app server depends on the technology stack and requirements of the web application being developed.