JSP pageContext Object

JSP pageContext Object is implicitly available to the developer on Java Server Pages. A pageContext implicit object is used for storing and retrieving page-related information and sharing objects within the same translation unit and same request. Also used as a convenience class that maintains a table of all the other implicit objects.

 It stores referece to the implicit objects-
The following example shows how PageContext is used to populate other implicit objects.
public void _jspService (HttpServletRequest request, HttpServletResponse response)
    throws java.io.IOException, ServletException { 

     ... 
    try { 

         ... 
        application = pageContext.getServletContext ();
        config = pageContext.getServletConfig ();
        session = pageContext.getSession ();
        out = pageContext.getOut (); 
         ... 

    } catch (Throwable t) {
         ... 
    } finally {
         ... 
    }
}

Provides convenience methods to get and set attributes in different scopes-
This example uses attributes to save and retrieve data in each of the four scopes:
<%
  // Save data
  pageContext.setAttribute("attr1", "value0");  // PAGE_SCOPE is the default
  pageContext.setAttribute("attr2", "value1", PageContext.PAGE_SCOPE);
  pageContext.setAttribute("attr3", "value2", PageContext.REQUEST_SCOPE);
  pageContext.setAttribute("attr4", "value3", PageContext.SESSION_SCOPE);
  pageContext.setAttribute("attr5", "value4", PageContext.APPLICATION_SCOPE);
%>
    
<%-- Show the values --%>
<%= pageContext.getAttribute("attr1") %>
<%= pageContext.getAttribute("attr2", PageContext.PAGE_SCOPE) %>
<%= pageContext.getAttribute("attr3", PageContext.REQUEST_SCOPE) %>
<%= pageContext.getAttribute("attr4", PageContext.SESSION_SCOPE) %>
<%= pageContext.getAttribute("attr5", PageContext.APPLICATION_SCOPE) %>

JSP pageContext Object Example:
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>JSP pageContext Object Example</title>
</head>
<body>
<%  
 JspWriter pw =  pageContext.getOut();
  pw.print("Hello Dinesh....This is another example of JSP 'pageContext' object");
%>
</body>
</html>
As you can see above, using JSP pageContext object, JspWriter instance is created. Using this JspWriter object, String response is set that displayed on the browser when JSP served a request.



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