What is the Flow of Requests in Struts-based applications?
In Struts-based applications, the flow of requests follows a specific pattern that is designed to separate concerns and facilitate the development of web applications. Struts is an open-source framework for building Java EE web applications, and it follows the Model-View-Controller (MVC) design pattern. Here’s a high-level overview of the flow of requests in a Struts-based application:
Client Request: The process begins when a client (usually a web browser) sends an HTTP request to the server. This request typically targets a specific URL that is mapped to a Struts action.
Action Mapping: The Struts framework uses a configuration file (usually struts-config.xml in Struts 1 or annotations in Struts 2) to map the incoming request URL to a specific action class. This mapping determines which action will handle the request.
Action Class: The mapped action class is instantiated, and its execute method is called. This method contains the business logic for processing the request. It may interact with the model (business layer) to retrieve or manipulate data.
Model Interaction: The action class may call services or data access objects (DAOs) to perform operations on the data. This is where the application logic is executed, and the necessary data is prepared for the view.
ActionForm (Struts 1): If using Struts 1, the action class may also interact with an ActionForm object, which is used to encapsulate the form data submitted by the client. The framework automatically populates this object with the request parameters.
Result Handling: After processing the request, the action class returns a result (usually a string) that indicates which view should be rendered next. This result is often referred to as a "forward" in Struts 1 or a "result" in Struts 2.
View Resolution: The framework uses the result to determine which JSP (JavaServer Page) or other view technology should be used to render the response. The view is responsible for presenting the data to the user.
Rendering the View: The selected JSP page is rendered, and any data that needs to be displayed (often stored in the request or session scope) is made available to the view. The JSP generates the HTML response.
Response to Client: Finally, the generated HTML is sent back to the client as an HTTP response. The client’s browser receives this response and renders the page for the user to see.
User Interaction: The user can then interact with the rendered page, which may involve submitting forms or clicking links, leading to new requests and repeating the flow.
The Struts request flow emphasizes a clear separation of concerns, with the controller (action classes) handling the request logic, the model managing the data, and the view rendering the user interface. This structure helps in maintaining and scaling web applications effectively.