» » Jsp life cycle


     
  • jsp engine controls the life cycle of jsp
  • Jsp life cycle is described by three life cycle methods and six life cycle phases

Jsp life cycle methods :

  • jspInit()
  • _jspService()
  • jspDestroy()
Jsp Life Cycle

  • Jspinit() method is invoked when JSP page is initialized.
  • The _jspService() method corresponds to the body of the jsp page.
  • This method is defined automatically by the JSp container and should never be defined y the JSP page author.

Jsp Life cycle Phases: 

  • Translation phase
  • Compilation phase
  • Instantiation phase
  • initialization phase
  • Servicing phase
  • Destruction phase

Jsp Life Cycle methods




  • Jsp engine calls jspInit() method only once during the initialization phase of a jsp.
  • similarly during destruction phase jsp engine calls jspDestory() method only once
  • For each client request Jsp container calls _jspService() method once.

Jsp Translation phase:

  • When client request comes for a jsp for the first time , jsp engine makes a full read of the jsp verifies the syntactical corectness of the jsp elements and converts code into a servlet source code .
  • The process of JSP engine translating jsp into servlet nothing but translation phase of JSP.
  • Therefore , we say that Jsp development is another style of development  asking container to develop the servlet is nothing but JSP developement
  • Container generated servlet class is also known as page implementation class.

Jsp Compilation phase:

  • The process of jsp engine compiling the page implementation class is nothing but compilation phase of jsp.
  • Jsp engine uses JASPER compiler to compile the container generated servlet class source code.
  • In the life of the Jsp Translation and compilation happens only once unless jsp source code modified.

Jsp Instantiation phase:

  • Container creating the instance of generated servelt class is nothing but instantialtion phase of jsp
  • actually now we have a servelt object.
  • Servlet engine loads user user defined servlet class file from secondary memory into
    primary memory dynamically

    class c= class.forName("name");
    c.newInstance();
  • Servlet engine creates the instance of loaded servlet class.
  • Servlet engine uses the following piece of code to load the servlet clas  dynamically to instantiate it.
    Class c= class.forName("Servlet class name");
    c.newInstance();


Initialization:

  • Servlet engine creates servletConfig object
  • Servlet engine calls the init() method on the servlet instance by supplying servletconfig object
    as argument.
  • Once init method completely executed servlet is ready to serve the client request.

Servicing : 

  • Servlet engine creates servlet request and servlet response object based on the web server
    provided client information.
  • Servlet engine calls service method on the servlet instance by supplying two object reference as arguments
  • Once service method is completely executed , client request is served and request-response cycle is complete.
  • Within the service method request object is used to capture the user input
  • Response object is used to build the dynamic page and hand over the same to the web server

Destruction:

  • Destruction phase of servlet represents servlet being removed from use by container

Instance Of Java

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