In HTTP Web applications, all requests have to be initiated by the Web client. Therefore, there is no way for the server to force a client to reload, other than as a response to a request from the client.
If you have a Web client that needs to be kept up to date with stuff that is happening on the server, you must poll the server periodically from the client. There is no way around this, within your architecture.
However, you do not need to reload the whole page on every poll. There are a variety of ways of avoiding this. AJAX is the current preference. Suggest you read up on it.
Note that the solution is likely to be almost entirely client-side code, and have little to do with
servlets.