alert « Message « JSP-Servlet Q&A

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

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.

2. Show error message using alert

Hi all, I have a JSP page for creating a user for an application. That has two pages, in the first page User's Personal details like userId , name and other params are got.In the next page User's privileges are assigned. Is there any possible way to check whether the provided userName already exists in the first page itself and show ...

3. can i give alert messages?