Life Cycle of JSP

JSP technology enables us to create web based application. It sends its request as a Servlet. Therefore, the life cycle and many of the capabilities of JSP pages (in particular the dynamic aspects) are determined by Java Servlet technology.

A Servlet handles the request that is mapped to a JSP page and checks whether the JSP page's servlet is older than the JSP page. Then it translates the JSP page into a servlet class and compiles the class.

JSP Life Cycle has three important methods that is:

1. init():- This method is called when the instance is created and it is called only once during JSP life cycle. It is called for the Servlet instance initialization.
2. service:- This method is called for every request of this JSP during its life cycle. It passes the request and the response objects. jspService() cannot be overridden.
3. destroy():- This method is called when this JSP is destroyed and will not be available for future requests.
   
   

Phases of JSP Life Cycle:

1. Translation:
   The JSP source file generates a java servlet file. Generated servlet implements the interface javax.servlet.jsp.HttpJspPage. The interface HttpJspPage extends the interface JspPage. This interface JspPage extends the interface javax.servlet.Servlet.
2. Compilation:
   The generated java servlet file is compiled into a java servlet class. The generated servlet class thus implements all the methods of the above said three (javax.servlet.jsp.HttpJspPage, JspPage, javax.servlet.Servlet) interfaces.
3. Class Loading:
   The java servlet class that was compiled from the JSP source is loaded into the container.
4. Instance Creation:
   An instance is created for the loaded servlet class. The interface JspPage contains jspInit() and jspDestroy(). The JSP specification has provided a special interface HttpJspPage for JSP pages serving HTTP requests and this interface contains _jspService().