
    /**
     * Queries against the datastore for all conferences and returns the result.
     *
     * @return A List of Conferences.
     */
    @ApiMethod(
            name = "queryConferences",
            path = "queryConferences",
            httpMethod = HttpMethod.POST
    )
    public List<Conference> queryConferences() {
        // Find all entities of type Conference
        Query<Conference> query = ofy().load().type(Conference.class).order("name");
    
        return query.list();
    }
    
    /**
     * Returns a list of Conferences that the user created.
     * In order to receive the websafeConferenceKey via the JSON params, uses a POST method.
     *
     * @param user A user who invokes this method, null when the user is not signed in.
     * @return a list of Conferences that the user created.
     * @throws UnauthorizedException when the user is not signed in.
     */
    @ApiMethod(
            name = "getConferencesCreated",
            path = "getConferencesCreated",
            httpMethod = HttpMethod.POST
    )
    public List<Conference> getConferencesCreated(final User user) throws UnauthorizedException {
        // If not signed in, throw a 401 error.
        if (user == null) {
            throw new UnauthorizedException("Authorization required");
        }
        String userId = user.getUserId();
        Key<Profile> userKey = Key.create(Profile.class, userId);
        return ofy().load().type(Conference.class)
                .ancestor(userKey)
                .order("name").list();
    }


    /**
     * Queries against the datastore for all conferences and returns the result.
     *
     * @return A List of Conferences.
     */
    @ApiMethod(
            name = "queryConferences",
            path = "queryConferences",
            httpMethod = HttpMethod.POST
    )
    public List<Conference> queryConferences() {
        // Find all entities of type Conference
        Query<Conference> query = ofy().load().type(Conference.class).order("name");
    
        return query.list();
    }
    
    /**
     * Returns a list of Conferences that the user created.
     * In order to receive the websafeConferenceKey via the JSON params, uses a POST method.
     *
     * @param user A user who invokes this method, null when the user is not signed in.
     * @return a list of Conferences that the user created.
     * @throws UnauthorizedException when the user is not signed in.
     */
    @ApiMethod(
            name = "getConferencesCreated",
            path = "getConferencesCreated",
            httpMethod = HttpMethod.POST
    )
    public List<Conference> getConferencesCreated(final User user) throws UnauthorizedException {
        // If not signed in, throw a 401 error.
        if (user == null) {
            throw new UnauthorizedException("Authorization required");
        }
        String userId = user.getUserId();
        Key<Profile> userKey = Key.create(Profile.class, userId);
        return ofy().load().type(Conference.class)
                .ancestor(userKey)
                .list();
    }

Update TODO_3_ConferenceApi.java