What is the execution flow of Struts2?

The main steps of the Struts2 execution process include:

1. The client sends a request: Users input the URL in their browser or send a request to the server by clicking on a link.
2. The web server receives the request: The web server receives a request sent by the client and forwards it to the Struts2 framework.
3. The Struts2 framework receives requests by intercepting and handling requests forwarded by the web server through a configured filter and interceptor chain.
4. Interceptor processing: In the Struts2 framework, requests are processed sequentially based on the configured interceptor chains. Interceptors can perform various operations, such as verifying user identity, logging, etc.
5. After passing through the interceptor chain, the Struts2 framework forwards the request to the relevant Action class for processing. The Action class is a POJO (Plain Old Java Object) that contains the implementation of business logic.
6. Business logic processing: Methods in the Action class handle business logic based on the request parameters, and can invoke methods from the service layer or data access layer.
7. After processing the business logic, the Action class will encapsulate the results into a result object and return it to the Struts2 framework.
8. Result Rendering: The Struts2 framework selects the appropriate result renderer based on the configured result type to render the results. Results can include HTML pages, JSON data, XML data, and more.
9. The result is returned to the client: after rendering is complete, Struts2 framework sends the rendered result back to the Web server.
10. The response is sent to the client: The web server sends the response to the client’s browser for parsing and display.

In summary, the execution process of Struts2 starts with a request from the client to the web server, then goes through the Struts2 framework’s interceptor chain handling, business logic processing in the Action class, before finally returning the results and rendering them, ultimately sending the response back to the client’s browser.