JSP Implicit Object's

During the translation phase, the jsp engine declares and initializes nine commonly used variables in the service method of the generated servlet. They are implicitly made available to a jsp without need of declaring them. These are known as implicit variables or implicit objects. They are as follows.

o   Request

o   Response

o   Session

o   Config

o   Application

o   Page

o   Exception

o   Out

o   pageContext

Request:- This object is of type javax.Servlet.http.HttpServletREquest. It refers to the current request to the jsp. By using this object we can capture the client data. For example in a scriptlet we can write as follows.

<%

            String name=request.getParameter(“html textbox name”);

%>

With the above scriptlet we can get the form data directly into the jsp.

Response:- This objet is of type javax.servlet.http.HttpServletResponse. It  is used for sending customized response to the client.

Session:- This object is of type javax.servlet.http.HttpSession. This object is not available in a jsp if we  say <%@ page session=”false” %>. In a servlet when we available in a jsp it is imlicitly available. If we want to implement session tracking in a jsp, we make use of this object.

Config:- The object is of type javax.servlet.ServletConfig. When initialization parameters are supplied to the jsp explicitly from the web.xml. we can retrieve them by using this object.

<% String paramvalue=config.getInitParameter(“Paramname”); %>

Application:- This is an object of type javax.servlet.ServletContext. It refers to the environment to which the jsp belongs. Using this object we can retrieve application level state. All the web components(Jsps & servlets) running in the same application can share common information. For example if a servlet or another jsp has stored some info in the ServletContext object, in our current jsp we can retrieve it as follows.

<%  String value=(String)application.getAttribute(“name”); %>

Page:- The is an object of type java.lang.object. It refers to the instance of the generated servlet. This is very rarely used in a jsp.

Exception:- This object