Apache Struts is an open-source framework for building web applications in Java. It’s part of the Apache Jakarta Project and provides a set of tools and components to simplify the development of web applications following the Model-View-Controller (MVC) architectural pattern. Here are some key points about Apache Struts:

1. MVC Architecture: Apache Struts enforces the MVC architecture, which separates an application into three main components:

   • Model: Represents the application’s data and business logic.
   • View: Handles the presentation layer, typically generating HTML or other content to be displayed in the user’s browser.
   • Controller: Manages the flow of the application, handling user requests, and updating the model and view accordingly.

2. Tag Libraries: Struts provides custom JSP (JavaServer Pages) tag libraries that simplify the creation of user interfaces in JSP pages. These tags help in binding form data, performing validation, and controlling navigation.

3. Validation Framework: Struts includes a powerful validation framework that allows developers to define validation rules for their application’s forms. It supports both server-side and client-side validation.

4. Action Classes: In Struts, action classes (usually extending the Action class) are responsible for handling user requests. These classes perform the necessary processing, interact with the model, and determine the next view to display.

5. Interceptors: Struts 2 (a later version of Struts) introduced the concept of interceptors, which allow developers to define cross-cutting concerns such as logging, security, or authentication in a modular way.

6. Integration: Struts can integrate with various view technologies, including JSP, FreeMarker, and Velocity, allowing flexibility in designing the user interface.

7. Security: Security features can be implemented using Struts, but it’s essential to configure security measures carefully to protect against common web application vulnerabilities.

8. Apache Struts 1 vs. Struts 2: There are two major versions of Struts: Struts 1 (legacy) and Struts 2 (also known as Apache Struts). Struts 2 is a complete rewrite and offers more flexibility and features compared to Struts 1.