
How to show the message "invalid username and password" after redirecting the page to the login form?

JSP Login validation
1)login.jsp:
<html>
<script>
function validate(){
var username=document.form.user.value;
var password=document.form.pass.value;
if(username==""){
alert("Enter Username!");
return false;
}
if(password==""){
alert("Enter Password!");
return false;
}
return true;
}
</script>
<form name="form" method="post" action="check.jsp" onsubmit="javascript:return validate();">
<table>
<tr><td>Username:</td><td><input type="text" name="user"></td></tr>
<tr><td>Password:</td><td><input type="password" name="pass"></td></tr>
<tr><td></td><td><input type="submit" value="Submit"></td></tr>
</table>
</form>
</html>
<%String msg=request.getParameter("msg");
if(msg!=null){
%>
<label><font color="red"><%=msg%></font></label>
<%
}
%>
2)check.jsp:
<%@page import="java.sql.*"%>
<%
String user=request.getParameter("user");
String pass=request.getParameter("pass");
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
Statement st=con.createStatement();
ResultSet rs=st.executeQuery("select * from login where username='"+user+"' and password='"+pass+"'");
int count=0;
while(rs.next())
{
count++;
}
if(count>0)
{
out.println("welcome "+user);
}
else
{
response.sendRedirect("login.jsp?msg=Invalid Username or Password");
}
%>
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