重定向到同一页面但其中有一条消息

Question

I am making a login page in JSP. I have an index.jsp page where exist the form and some javascript scriplets. Connectivity to oracle database and checking for username and password in database is done in check1.jsp file

My issue is after entering username and password, when I press login button, I have linked the form to check1.jsp , if username and password matches and exist, it redirects to welcome.jsp , but if username doesnot exist or password is not matched I have to get back to index.jsp showing a small message below box that username doesn't exist OR Password is not matched , currently I am just redirecting to index.jsp .

How should I show that appropriate small message below login box on that same index.jsp page??

Answer 1

You can use session object here:

In check1.jsp :

if (loginSuccess) {
    //redirect to welcome.jsp
}
else {
    session.setAttribute("error", "Username or Password is incorrect");
    //redirect to index.jsp
}

In index.jsp :

String msg = session.getAttribute("error");
if (msg != null) {
    %><p style="color:red"><%= msg %></p><%
}

Also there is other more simpler ways exists with EL and JSTL, but its just for an starting tip.

Answer 2

You should not redirect to index.jsp, but forward to index.jsp in this case. Store the message in some request attribute, forward to the index.jsp, and display the message if it's present in the request attribute.

You should use an MVC framework, in order to always make your URLs point to actions (controllers) implemented in Java, make these actions call the business ogic (here, log the user in) and have those actions forward or redirect to the appropriate view (index.jsp or welcome.jsp).