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During translation phase, the JSP engine declares and initializing a commonly used

variables in the ser vice method of the generated servlet. They are implicitly made

available to a JSP without need of declaring them. These are called implicit variables or objects.

1. request

2. response3. session

4. config

5. application6. page

7. exception

8. out

9. pageContext

1. request:

this object is of type javax.servlet.http.HttpServletRequest. it refers to the current request

to theJSP. By using this object we captupre the client data

ex: in a scriptlet we write<% String name=request.getParameter(“html textbox name”%>

In the above we get the form data directly into the JSP.

2.response:this object is of type javax.servlet.http.HttpServletResponse. it is used for 

sending customize response to client.

3.session: this object is of type javax.servlet.http.HttpSession. this is not available in jsp.In a servlet when we implement session tracking , we call method getSession() on therequest object. In a JSP it is implicitly available. If we want to implement session

tracking in a JSP we use this object.

4.config: this object is of type javax.servlet.ServletConfig. when initialization

 parameaters are supplied to the JSP explicitly from the Web.xml, we can retrieve them by

using this object.

<%String paramvalue=config.getInitParameter(“paramname”)%>5.application:

this object is of type javax.servlet.ServletContext. it refers to the environment to which

 jsp belongs. Using this we retrieve the application level state.Ex: in a servlet or another jsp has stored some information in ServletContext obj, in our 

current jsp we retrieve it as

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

6.page:

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this is of type java.lang.Object. it refers to the instance of the generated servlest. This is

used rarely in JSP

7. exception:this is of type java.lang.Throwable. this is not available in all jsps. These pages which

are designated as errorpages, can access this object

ex: <% @page isErrorPatge=”true”%>

8.out: this is of the type javax.servlset.jsp.jspWriter. it refers to the output stream for the page. This is used to send html context from the jsp

9. pageContext: this is of the type javax.servlest. jsp.jspPageContext. it refers to the pageenvironment. It does 3 thing

1. it stores reference to the implicit objects. By supplying this single object to any

 java helperclass,k we supply all implict objects. That helper calss can retrieve allthe implict by calling getXXXXX() methods on the PageContext object.

Ex: ServletContext context= pageContext.getServletContext();

ServletConfig config= pageContext.getConfig();

HttpSession session= pageContext.getSession();

2. it provides methods to get and set attributes in different scopes

3. it provides methods to dispatching request to other resources on the web

application.Ex: pageContext.include(String relativeurl);

pageContext.forward(String relativeurl);