HTML/CSS/JavaScript runs at the client side. Java/JSP runs at the server side. The client and server are two distinct environments which usually runs at physically different machines, connected with each other by a network with the communication protocol being HTTP.

When the client requests a specific URL at the server, the server will run specific Java/JSP code and return a HTML/CSS/JS response back to the client. The client (webbrowser) will in turn execute the HTML/CSS/JS.

Knowing this fact, it should be obvious that the only way to let JavaScript access/invoke some Java/JSP code is to send a HTTP request to the server side. This can be done in several ways: using window.location to do a synchronous GET request, or form.submit() to do a synchronous GET or POST request, or XMLHttpRequest#send() to do an asynchronous (ajaxical) request.

But you after all don't need JavaScript for this at all. A simple HTML link or form is also sufficient.

<a href=page.jsp>link</a>

or

<form action=page.jsp>

    <input type=submit>

</form>

This will open the JSP file. If you'd like to run some business stuff prior to opening the JSP page, then better let the URL point to a Servlet like <a href=page> which in turn forwards the request to the JSP page like

request.getRequestDispatcher(/WEB-INF/page.jsp).forward(request, response);

To learn more about the wall between Java/JSP and JavaScript you may find this article useful.