How to give alert message in servlet and redirected it to jsp page

Question

i am developing some kind of pubsub application,so when a user subscribe to particular entity then he receive a alert for successful subscription and redirect on the same page.

Answer 1

In Servlet

session.setAttribute("Login_Expired","Expired") ;
response.sendRedirect("jsp/page.jsp");

In JSP

<%
String strExpired = (String) session.getAttribute("Login_Expired");
if (strExpired.equals("Expired")){     
out.print("alert('Password expired, please update your password..');");
}      
%>

Answer 2

Add an attribute in request from servlet and forward request to jsp on jsp use following

request.setAttribute("subscribed",true);

on jsp, in javascript

if(${subscribed == 'true'}){
  alert("Peep Peep..");
}

Answer 3

In servlet

String strExpired = (String) session.getAttribute("Login_Expired");
response.sendRedirect("jsp/page.jsp");

In jsp

<%
String strExpired = (String) session.getAttribute("Login_Expired");
out.print("alert('Password expired, please update your password..');");
%>