Listen to tomcat realm authentication events

Question

I need to know when tomcat accepts a login using realm authentication for a given context. I've been looking at the possible listeners available (ServletContextListener and ServletContextAttributeListener) but can't figure out how to be notified when a login occurs. This should also work when using tomcat single sign on for multiple contexts. Any ideas?

Answer 1

If you have access to the server configuration, you might try writing a LifecycleListener (http://tomcat.apache.org/tomcat-6.0-doc/api/org/apache/catalina/LifecycleListener.html), which are configured with the server (see the tomcat server config docs for your version).

Not sure if it will do the trick or not, but a good place to check.

Good luck.

Answer 2

Unfortunately there's no standard/abstract way to hook on it using the Servlet API. You need either to write appserver specific logic or to implement a global Filter which checks the HttpServletRequest#getUserPrincipal() everytime. E.g.:

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
    HttpServletRequest httpRequest = (HttpServletRequest) request;
    UserPrincipal user = httpRequest.getUserPrincipal();
    HttpSession session = httpRequest.getSession();
    if (user != null && session.getAttribute("user") == null) {
        session.setAttribute("user", user);

        // First-time login. You can do your intercepting thing here.
    }
    chain.doFilter(request, response);
}