Implicit Objects in JSP with example.

Implicit objects in JSP is created by the web container. There are total 9 implicit objects are available in JSP. objects are available for the complete JSP page.

Following are the Implicit Objects in JSP.

request Implicit Objects in JSP

  • The request object is an instance of the class which is implements java .servlet.http.HttpServletRequest interface.
  • Created by the container for every request.
  • request Object is used to request the information like header information, parameter, server name.
  • getParameter() method is used to access the request from the request object.
<%   
String name=request.getParameter("name");  
out.print("welcome "+name);  
%>

response Objects in JSP

  • The response is an instance of the class which implements HttpServletResponse interface.
  • It will be created by the container for each request.
  • It will help to send a response to the client.
  • Mostly it is used to redirect to response page and add the cookie.
<%   
response.sendRedirect("http://www.codebun.com");  
%>

session object in JSP.

  • The session is holding “httpsession” object.
  • A session object is used to get, set and remove attributes to session scope and also used to get session information.

For example, A real-time example when a user login to a website a session object is created for that user and complete profile of that user will be managed by the session object.

Set a session.

<%   
  
String name=request.getParameter("uname");  
 
session.setAttribute("session_name",name);  
  

%>

Get the session at any page in the application.

<%   
  
String name=(String)session.getAttribute("session_name");  
out.print("Hello "+name);  
  
%>

config object in JSP.

  • “config” is of the type java.servlet.servletConfig.
  • A ServletConfig object is created by web container for each servlet to pass information to a servlet during initialization.
  • This object can be used to get configuration information from a web.xml file.

web.xml

<init-param>  
<param-name>var_name</param-name>  
<param-value>Welcome to codebun.com</param-value>  
</init-param>

index.jsp

<%
String message=config.getInitParameter("var_name");  
out.print("driver name is="+message);  

%>

application object in JSP.

  • Application object is an instance of javax.servlet.ServletContext.
  • It is used to get the context information and attributes in JSP.
  • Application object is created by the container.
  • Servletcontext object contains a set of methods which are used to interact with the servlet container.
  • We can find information about the servlet container.

web.xml

<context-param>  
<param-name>var_name</param-name>  
<param-value>Welcome to codebun.com</param-value>  
</context-param>  

index.jsp

<%
String message=application.getInitParameter("var_name");  
out.print("driver name is="+message);  

%>

 pageContext object in JSP.

  • This object is of the type of pagecontext.
  • It is used to get, set and remove the attributes from a particular scope.

There is four type of objects.

  • Page
  • Request
  • Session
  • Application
<% pageContext.setAttribute("key_var","Value : hello JSP Welcome to codebun",pageContext.PAGE_SCOPE);
String msg= (String)pageContext.getAttribute("key_var");
out.println("Message : " +msg);
%>

page object in JSP.

  • Page implicit variable holds the currently executed servlet object for the corresponding JSP.
  • Type of page is Object.
  • Acts as this object for current JSP page.
<% String page_name = page.toString();
out.println("Page Name is " +page_name);%>

exception object in JSP.

  • An exception is the implicit object of the Throwable class.
  • It is used for exception handling in JSP.
<%@ page isErrorPage="true" %>  
<html>  
<body>  
  
Exception occured:<%= exception %>  
  
</body>  
</html>

out Object in JSP.

Out is object of javax.servlet.jsp.jspWriter class.

  • Out is one of the implicit objects to send output to the client as a response.
  • Out object allows us to access the servlet’s output stream.
  • In Jsp web don’t need to create an object of PrintWriter but in Servlet we need to define object of printWriter like”PrintWriter out=response.getWriter(); “
<html>  
<body>  
<% out.print("Welcome to codebun.com! Enjoy learning"); %>  
</body>  
</html>

 

 

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