java - Where are the attributes stored, which are set by servlets? -
below servlet:
public class servletexample extends httpservlet { private static final long serialversionuid = 1l; protected void service(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { if(request.getparameter("firstname") == null || request.getparameter("lastname") == null){ this.getservletcontext().getrequestdispatcher("/index.jsp").forward(request, response); return; } string firstname = request.getparameter("firstname"); string lastname = request.getparameter("lastname"); request.setattribute("firstname", firstname); request.setattribute("lastname", lastname); this.getservletcontext().getrequestdispatcher("/output.jsp").forward(request, response); } } below index.jsp:
<?xml version="1.0" encoding="iso-8859-1" ?> <%@ page language="java" contenttype="text/html; charset=iso-8859-1" pageencoding="iso-8859-1"%> <!doctype html public "-//w3c//dtd xhtml 1.0 transitional//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="content-type" content="text/html; charset=iso-8859-1" /> <title>insert title here</title> </head> <body> <form action="servletexample" method="post" > <table border="0"> <tr> <td>first name:</td> <td><input type="text" name="firstname" /></td> </tr> <tr> <td>last name:</td> <td><input type="text" name="lastname" /></td> </tr> <tr> <td colspan="2"> <input type="submit" value="submit" /></td> </tr> </table> </form> </body> </html> below output.jsp:
<?xml version="1.0" encoding="iso-8859-1" ?> <%@ page language="java" contenttype="text/html; charset=iso-8859-1" pageencoding="iso-8859-1"%> <!doctype html public "-//w3c//dtd xhtml 1.0 transitional//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="content-type" content="text/html; charset=iso-8859-1" /> <title>insert title here</title> </head> <body> <h1>your first , last name is: </h1> <% /*string firstname = (string)request.getattribute("firstname"); string lastname = (string)request.getattribute("lastname");*/ string firstname = request.getparameter("firstname"); string lastname = request.getparameter("lastname"); out.print(firstname + " " + lastname); %> </body> </html> i learnt that, when webapplication gets loaded, servletcontainer create servletcontext once , keep in server's memory. servletcontext collection of attributes , configurations apply entirety of web application
as per above servletexample, request.setattribute used create new attribute.
1)
are these attributes stored in servletcontext?
2)
what attributes , configurations stored in servletcontext?
there 3 scopes:
- application scope (i.e. sevletcontext)
- session scope (i.e. httpsession)
- request scope (i.e. httpservletrequest)
getting servletcontext object:
getservletcontext().set attribute("name","value"); //now name attribute accessible servlet within application.
getting httpsession object:
request.getsession(true).set attribute("name2","value"); //now name2 attribute accessible current session
request.set attribute("name3","value");
//now name3 attribute accessible anywhere in servlet or jsp before sending response client.
ques:where attributes stored?
ans: attributes stored in map(in name-value pair) of respective scope. i.e. session map, request map , servletcontext map.
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