Java Server Pages (JSP) requests are handled through a well-defined lifecycle, which involves several stages from the initial receipt of the client request to the final delivery of the server response. Here's a detailed breakdown of how JSP requests are processed:
1. Translation and Compilation
The first step in handling a JSP request is the translation of the JSP page into a Java servlet. This process is triggered the first time the JSP page is requested or if the JSP page has been modified since its last compilation[1][2][4][5]. During translation, the JSP engine parses the JSP file, converting it into a Java servlet source code. This servlet code is then compiled into a Java class by the JSP engine[1][4][5].
2. Loading and Instantiation
Once compiled, the servlet class is loaded into the JSP container. The container then creates an instance of the servlet class, preparing it to handle requests[1][4]. This instantiation process involves initializing any objects that the servlet might need to process requests.
3. Initialization
After instantiation, the jspInit() method is called. This method is designed for any initialization code that needs to run before the servlet begins handling requests. It's typically used to set up resources like database connections or configuration settings[1][4].
4. Request Processing
When a client request is made to the JSP page, the JSP engine invokes the _jspService() method on the instantiated servlet. This method is responsible for processing the incoming HTTP request and generating the appropriate response. The _jspService() method takes HttpServletRequest and HttpServletResponse objects as parameters, which represent the client's request and the server's response, respectively[1][4][5]. This method handles all types of HTTP requests (GET, POST, etc.) and cannot be overridden[1].
5. Cleanup
Finally, when the JSP page is about to be removed from use (either due to server shutdown or if it's being undeployed), the jspDestroy() method is called. This method is used for cleanup activities, such as releasing resources, closing database connections, or cleani...
