How can I alert message in Servlet code and sendredirect to JSP page?

Question

I am trying to make a simple login page to deal with database using JSP, servlet with MVC concept and Data Access Object(DAO) and I am new in this. My problem now that I need to alert a box message in servlet if the user enters invalid name and password and sendRedirect to login.jsp page again. I set flag to be 1 if the user valid then do this if-check

if(validUserFlage == 1)
    response.sendRedirect("User_Manipulation_Interface.jsp");
else {   
    //Here i want to alert message cause user invalid ??
    response.sendRedirect("Admin_And_User_Login_Form.jsp");
}

searching for this i find this answer but i can`t understand how can i do it the answer i found: (( With send redirect you cant display the message where you want in the code. So as per me there might be two approaches. Display a message here and use include of requestdispatcher instead of send redirect or else pass some message to admin.jsp and display the message there. ))

In our servlets wiki page you can find a hello world example with validation: http://stackoverflow.com/tags/servlets/info — BalusC, Feb 24 '12 at 13:55

score 3 · Answer 1 · answered Feb 24 '12 at 07:44

3

Set a flag parameter like this,

 response.sendRedirect("Admin_And_User_Login_Form.jsp?invalid=true");

on jsp

<c:if test=${invalid eq 'true'}">invalid credentials</c:if>

answered Feb 24 '12 at 07:44

jmj

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ok, but in jsp page i trying to get the value send in URL invalid = request.getParameter("invalid"); for now i want to check if the invalid is true or false and if it false then alert message with javascript for example to tell the user that his input invalid Really i am new in jsp and i can not understand the last line from your answer Could you help me in more simple way ! – Eman Hassan Feb 24 '12 at 08:12
set that flag to some hidden field on your jsp from java script after load check if that field contains true then alert – jmj Feb 24 '12 at 08:29

score 2 · Answer 2 · answered Feb 24 '12 at 09:47

You can set the Parameters like errormsg in the servlet page and add it to the ri-direct object. Then you can check that variable errormsg and if it is null then the username is correct else the username is incorrect..

In Servlet Code:
if(username.equal(databaseusername))

{
RequestDispatcher rd = request.getRequestDispatcher("NextPage.jsp");

req.setAttribute("errormsg", "");

rd.forward(request, response);  

}

else

{

RequestDispatcher rd = request.getRequestDispatcher("login.jsp");

req.setAttribute("errormsg", "Wrong Username or Password");

rd.forward(request, response);  

}

In JSP code:

<%

String msg=req.getAttribute("errormsg").toString();

if(!msg.equals(""))

{

// Print here the value of Msg.

}


%>

score 0 · Answer 3 · answered Mar 26 '12 at 08:54

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..');");

%>

How can I alert message in Servlet code and sendredirect to JSP page?

3 Answers3

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