Question

I’m using GWT and RequestFactory on a new project that needs authentication.

Where would be the best place to add the login and logout functions ? in a UserRequestContext ?

Thanks in advance.

Answer 1

Use servlet filter.

I split RequestFactory calls into two streams – one for unauthenticated calls and another one for authenticated ones. Here is piece of my web.xml.

<servlet>
    <servlet-name>CustomRequestFactoryServlet</servlet-name>
    <servlet-class>my.server.CustomRequestFactoryServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>CustomRequestFactoryServlet</servlet-name>
    <url-pattern>/gwtRequest</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>CustomRequestFactoryServlet</servlet-name>
    <url-pattern>/gwtRequestAuth</url-pattern>
</servlet-mapping>

Then I created servlet filter which looks like this:

public class GaeAuthFilter implements Filter
{
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
    {
        UserService userService = UserServiceFactory.getUserService();
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        if (!userService.isUserLoggedIn())
        {
            String returnURI = "/";

            String requestURI = request.getRequestURI();
            String refererURI = request.getHeader("Referer");
            if (requestURI.equals("/gwtRequestAuth"))
            {
                if (refererURI != null)
                    returnURI = refererURI;
            } else
                returnURI = requestURI;

            response.setHeader("login", userService.createLoginURL(returnURI));
            response.sendError(HttpServletResponse.SC_UNAUTHORIZED);
            return;
        }

        LoginService.login(request);

        filterChain.doFilter(request, response);
    }
}

As you can see I set login http-header with URL to auth webpage.

In the client code I intercept it by implementing my own DefaultRequestTransport that looks ike this:

public class GaeAuthRequestTransport extends DefaultRequestTransport
{
    private final EventBus eventBus;

    public GaeAuthRequestTransport(EventBus eventBus)
    {
        this.eventBus = eventBus;
    }

    @Override
    protected RequestCallback createRequestCallback(final TransportReceiver receiver)
    {
        final RequestCallback superCallback = super.createRequestCallback(receiver);

        return new RequestCallback()
        {
            public void onResponseReceived(Request request, Response response)
            {
                if (Response.SC_UNAUTHORIZED == response.getStatusCode())
                {
                    String loginUrl = response.getHeader("login");
                    if (loginUrl != null)
                    {
                        receiver.onTransportFailure(new ServerFailure(
                                "Unauthenticated user", null, null, false /* not fatal */));
                        eventBus.fireEvent(new GaeAuthenticationFailureEvent(loginUrl));
                        return;
                    }
                }
                superCallback.onResponseReceived(request, response);
            }

            public void onError(Request request, Throwable exception)
            {
                superCallback.onError(request, exception);
            }
        };
    }
}

Fired event is handled in the client code that navigates browser to login URL.

That’s it.