Struts 2 is a popular Java web application framework that follows the Model-View-Controller (MVC) design pattern. Here is an overview of the Struts 2 architecture and flow:

1. Request handling: When a user submits a request, it is first handled by the Struts 2 filter, which intercepts all requests and forwards them to the Struts 2 framework. The Struts 2 filter is responsible for initializing the framework and its components.

2. Action handling: Once the request is intercepted by the Struts 2 filter, it is processed by the ActionServlet. The ActionServlet is responsible for finding the appropriate action class to handle the request. The ActionServlet uses the ActionMapper to determine which action class should be used based on the request URL.

3. Interceptor handling: Before the action class is executed, it may pass through one or more interceptors. Interceptors are responsible for performing cross-cutting concerns such as logging, security, or validation. The interceptors can modify the request, response, or action before and after the action execution.

4. Action execution: The action class is responsible for processing the request and generating a response. The action class contains the business logic and can access the model or any service components to produce the response. After the action execution, it returns a result code to the ActionServlet.

5. Result processing: Once the action execution is complete, the result code is used by the ActionServlet to identify which result type should be used to generate the response. The result type determines how the response will be generated, such as a JSP page, a JSON object, or a PDF document.

6. Response generation: The result type generates the response, and the response is sent back to the client. The response may also pass through one or more interceptors before it is sent to the client. The interceptors can modify the response content or header, apply caching or compression, or handle errors.

Overall, this architecture and flow provide a clear separation of concerns and a modular approach to building web applications in Java. The Model-View-Controller pattern allows for a clean separation of business logic, presentation, and user input handling, which results in a more maintainable and scalable application.