Accessing Tomcat Context Path from Servlet

public void init(final ServletConfig config) {
    final String context = config.getServletContext().getRealPath("/");
    ...
}

...

public class MyServlet extends HttpServlet {

    public void init(final ServletConfig config) {
        final String context = config.getServletContext();
        ...
    }

    ...
}

File file = new File(getServletContext().getResource("/js/file.js").getFile());

InputStream input = getServletContext().getResourceAsStream("/js/file.js");