JSP Response Object

JSP Response Object is implicitly available to the developer on Java Server Pages. This object implements javax.servlet.ServletResponse interface. It is useful object in setting response to serve the request. This object has a scope for that specific request. "HttpServletResponse" class and using this object, response parameters can be modified or set. The response object handles the output of the client. The response object is generally used by cookies. The response object is also used with HTTP Headers.
Methods of response object
  • setContentType()
  • addCookie(Cookie cookie)
  • addHeader(String name, String value)
  • containsHeader(String name)
  • setHeader(String name, String value)
  • sendRedirect(String)
  • sendError(int status_code)
setContentType():

The "setContentType()" method of response object is used to set the MIME type and character encoding for the page.
Example :
response.setContentType("text/html");

addCookie(Cookie cookie):

This method is used to add the specified cookie to the response . If you wants to add more than one cookie, then use this method by calling it as many times as required.
Example :
response.addCookie(Cookie dineshonjava) ;

addHeader(String name, String value):

This method is used to write the header to the response as pair of name and value. If the header is already present, then value is added to the existing header values. General syntax of addHeader() of response object is as follows:
response.addHeader(String name, String value)
Example :
response.addHeader("User", "Dinesh") ;

containsHeader(String name):

The "containsHeader()" method of response object is used to check whether the header, given as parameter, already included to the response or not. If the named response header is set then it returns a true value. If the named response header is not set, the value is returned as false.
Example :
response.containsHeader(String Author)

setHeader(String name, String value):

This method is used to write the header to the response as pair of name and value a string. If the header is already present, then the original value is replaced by the current value given as parameter in this method. General syntax of "setHeader" of response object is as follows
response.setHeader(String name, String value)
Example:
response.setHeader("Content_Type","text/html");

sendRedirect(String):

This method is used to send a response which redirect client to new page. But one must note that if the JSP, in execution, has already sent page content to the client, then the "sendRedirect()" method of response object will not work and will fail. General syntax of sendRedirect of response object is as follows:
response.sendRedirect(String)
Example :
response.sendRedirect("http://www.dineshonjava.com/") ;

sendError(int status_code , java.lang.String msg) :

Sends an error response to the client using the specified status code and descriptive message. If the response has already been committed, this method throws an "IllegalStateException". After using this method, the response should be considered to be committed and should not be written to.

JSP Response 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">
<%@page import="java.io.PrintWriter"%>
<html>
<head>
<title>JSP Request Object Example</title>
</head>
<body>
<%  
 PrintWriter pw =  response.getWriter();
  pw.print("Hello Dinesh....This is an example of JSP 'Response' object");
%>
</body>
</html>

Output on Browser: Hello Dinesh....This is example of JSP 'Response' object

As you can see above, using JSP response object, PrintWriter instance is created. Using this PrintWriter object, String response is set that displayed on the browser when JSP served a request.

Copy implicitobjects folder on webapp directory of tomcat at
C:\Program Files (x86)\Apache Software Foundation\Tomcat 7.0\webapps\

and restart server and hit the following URL
http://localhost:8080/implicitobjects/index.jsp



Download Example.


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