2.4/samples/expenses/src/main/java/com/google/gwt/sample/gaerequest/client/GaeAuthRequestTransport.java

/*
 * Copyright 2010 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.sample.gaerequest.client;

import com.google.gwt.event.shared.EventBus;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.Response;
import com.google.web.bindery.requestfactory.gwt.client.DefaultRequestTransport;
import com.google.web.bindery.requestfactory.shared.ServerFailure;

/**
 * Extends DefaultRequestTransport to handle the authentication failures
 * reported by {@link com.google.gwt.sample.gaerequest.server.GaeAuthFilter}
 */
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) {
        /*
         * The GaeAuthFailure filter responds with Response.SC_UNAUTHORIZED and
         * adds a "login" url header if the user is not logged in. When we
         * receive that combo, post an event so that the app can handle things
         * as it sees fit.
         */

        if (Response.SC_UNAUTHORIZED == response.getStatusCode()) {
          String loginUrl = response.getHeader("login");
          if (loginUrl != null) {
            /*
             * Hand the receiver a non-fatal callback, so that
             * com.google.web.bindery.requestfactory.shared.Receiver will not post a
             * runtime exception.
             */
            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);
      }
    };
  }
}