The topic I’m writing about is quite common, and most people are already familiar with it. So, why am I writing this blog? The reason is simple: understanding these concepts was challenging when I was a beginner in web development. As a newbie to Nginx and other web servers, I often found myself confused. Every article I read would say that Nginx is a web server and that WildFly (which I encountered while working with Keycloak) is an application server. But back then, understanding the difference between the two wasn't as easy as it seems now.
In this blog, I aim to explain the difference between application servers and web servers in a beginner-friendly way, based on my own learning experiences.
Server
Before knowing about web servers and application servers, let’s first understand what a server is. A server is another machine or program that provides functionality and services to other devices or programs(known as a client). For example, when you want to read this blog, you click the link in your browser. Your browser then calls the URL, which the DNS (Domain Name System) translates into the IP address of the machine where this website is hosted. That machine then returns the content of this blog to your browser. In this scenario, that machine is called a server.
Web server
A web server is a type of server that delivers web page content such as HTML, CSS, JavaScript, and images using HTTP protocols. When you click a link in your browser, your request is sent to a web server, which processes the request and returns the requested content. Web servers are primarily designed to serve static content. However, static content alone isn't sufficient for many modern applications. Often, we need to process requests and generate dynamic content based on user interactions or data. In such cases, the web server works in conjunction with an application server to process the request and deliver the appropriate dynamic content.
Some of the most widely used modern web servers in the industry include Nginx, Apache HTTP server, and Microsoft IIS.
Application server
An application server is designed to handle business logic and serve dynamic content by interacting with various hardware components such as databases. When a web server needs data to fulfill a request, it interacts with the application server to retrieve that data. The application server acts as middleware between the web server and the underlying resources.
Some of the most widely used modern application servers in the industry include WebSphere, WildFly, and GlassFish.
Example
When you want to read this blog, you first connect to the web server. The web server serves the static content like HTML, CSS, and JavaScript. However, it doesn’t have dynamic content, such as the data of this blog post. To retrieve that data, the web server calls the application server. The application server then interacts with the database to get the necessary data and returns it to the web server. Finally, the web server compiles the full page, combining static and dynamic content, and sends it back to the user.
Major differences
| Feature | Web Server | Application Server |
|---|---|---|
| Primary Function | Serves static content (HTML, CSS, JavaScript, images) | Serves dynamic content by executing application logic and interacting with databases or other resources |
| Example Use Case | Delivering a simple website with static pages | Delivering a complex web application that requires user-specific data or real-time processing |
| Interaction | Handles HTTP requests and responses directly | Processes business logic and communicates with databases, web services, and other resources |
| Examples | Apache HTTP Server, Nginx, Microsoft IIS | Apache Tomcat, WildFly, GlassFish, IBM WebSphere, Oracle WebLogic |
| Support for Protocols | Primarily HTTP/HTTPS | Supports a variety of protocols (HTTP, SOAP, REST, RMI, etc.) for communication between applications and services |
| Configuration | Configured to handle static file serving, URL routing, and caching | Configured to manage application deployment, transaction handling, and resource pooling |
Conclusion
Both application servers and web servers are essential components of modern web development. In recent times, many of the tasks traditionally handled by application servers have been managed by frameworks, but it's still crucial to understand how both types of servers work. I hope this provided a simple and clear introduction to the roles of web servers and application servers.
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