JSP Life Cycle

Every JSP page must be converted into an instance of a servlet class before it can be used to service client requests.

JSP life-cycle phases

Page translation - The page is parsed and a Java file containing the corresponding servlet is created.
Page compilation - The Java file is compiled.
Load class - The compiled class is loaded.
Create instance - An instance of the servlet is created.
Call jspInit() - This method is called before any other method to allow initialization.
Call _jspService() - This method is called for each request.
Call jspDestroy() - This method is called when the servlet container decides to take the
servlet out of service.

life-cycle mehtods in JSP

The generated servlet class for a JSP page implements the HttpJspPage interface of the javax.servlet.jsp package. Hte HttpJspPage interface extends the JspPage interface which inturn extends the Servlet interface of the javax.servlet package. the generated servlet class thus implements all the methods of the these three interfaces. The JspPage interface declares only two mehtods - jspInit() and jspDestroy() that must be implemented by all JSP pages regardless of the client-server protocol. However the JSP specification has provided the HttpJspPage interfaec specifically for the JSp pages serving HTTP requests. This interface declares one method _jspService().
The jspInit()- The container calls the jspInit() to initialize te servlet instance.It is called before any other method, and is called only once for a servlet instance.
The _jspservice()- The container calls the _jspservice() for each request, passing it the request and the response objects.
The jspDestroy()- The container calls this when it decides take the instance out of service. It is the last method called n the servlet instance.

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