A JSP page is converted into servlet before service requests. JSP Lifecycle consists of following phases:
JSP Page Translation:
The container validates the JSP page and parse it to generate the servlet file.
JSP Page Compilation:
The generated servlet file is compiled into a servlet class.
Container loads the generated servlet class into memory.
Container invokes the no argument constructor of generated servlet class to load it into memory and instantiate it.
After creating the instance, jspInit() method is called to initialize it.
The _jspService() is called by web container every time when a request is come for the jsp.
public void _jspService() throws ServletException,IOException
Note: In this method underscore (_) represents that implementation of this method is provided by auto generated servlet and it can’t be overridden by developer.
The jspDestroy() method is called by web container to unload JSP from memory.