protected void doPost(HttpServletRequest request,
		HttpServletResponse response) throws ServletException, IOException {
	HttpSession session = request.getSession();

	// Call back from Twitter
	String oauthToken = request.getParameter(PARAM_OAUTH_TOKEN);
	if (oauthToken != null) {
		logger.debug(PARAM_OAUTH_TOKEN + " received from Twitter");
		try {
			Twitter twitter = (Twitter) session.getAttribute(ATTR_TWITTER);
			RequestToken requestToken = (RequestToken) session
					.getAttribute(ATTR_REQUEST_TOKEN);
			AccessToken accessToken;
			if (callbackUrl == null) {
				accessToken = twitter.getOAuthAccessToken(requestToken);
			} else {
				String oauthVerifier = request
						.getParameter(PARAM_OAUTH_VERIFIER);
				logger.debug(PARAM_OAUTH_VERIFIER
						+ " received from Twitter");
				accessToken = twitter.getOAuthAccessToken(requestToken
					.getToken(), requestToken.getTokenSecret(),
					oauthVerifier);
			}
			twitter.setOAuthAccessToken(accessToken);
			session.removeAttribute(ATTR_REQUEST_TOKEN);
			session.setAttribute(ATTR_TWITTER, twitter);

			int id = twitter.verifyCredentials().getId();
			logger.debug("Access token retrieved for user " + id
					+ " from Twitter");
			storeAccessToken(id, accessToken);
			Cookie cookie = new Cookie(COOKIE_TWITTER_ID, "" + id);
			cookie.setMaxAge(63072000); // Valid for 2 years
			response.addCookie(cookie);
			logger.debug("Cookie set for user " + id);

			// Get last status and friends' timelines
			getMyLastStatusAndStoreInSession(session);
			getFriendsTimelinesAndStoreInSession(session);

			// Go to the update status page
			request.getRequestDispatcher(PAGE_UPDATE_STATUS).forward(
					request, response);
		} catch (TwitterException e) {
			logger.error("Failed to retrieve access token - "
					+ e.getMessage());
			throw new ServletException(e);
		}
	}

	// Actions within this application
	String action = request.getParameter(PARAM_ACTION);
	if (ACTION_SIGN_IN.equals(action)) {
		logger.debug("Signing in with Twitter...");
		Twitter twitter = new Twitter();
		twitter.setOAuthConsumer(consumerKey, consumerSecret);

		// Try to load Twitter ID from cookies
		String id = null;
		Cookie[] cookies = request.getCookies();
		if (cookies != null) {
			Cookie cookie;
			for (int i = 0; i < cookies.length; i++) {
				cookie = cookies[i];
				if (COOKIE_TWITTER_ID.equals(cookie.getName())) {
					id = cookie.getValue();
				}
			}
		}

		// Try to load access token if user's Twitter ID is retrieved
		AccessToken accessToken = null;
		if (id != null) {
			accessToken = loadAccessToken(id);
			if (accessToken != null) {
				twitter.setOAuthAccessToken(accessToken);
				session.setAttribute(ATTR_TWITTER, twitter);

				// Get last status and friends' timelines
				try {
					getMyLastStatusAndStoreInSession(session);
					getFriendsTimelinesAndStoreInSession(
						session, true);
				} catch (TwitterException e) {
					e.printStackTrace();
				}

				// Access token loaded, go the up update status page
				logger.debug("Going to the status update page...");
				request.getRequestDispatcher(PAGE_UPDATE_STATUS).forward(
						request, response);
			}
		}

		// Can not load access token, go to Twitter for authentication
		if (accessToken == null) {
			try {
				RequestToken requestToken;
				if (callbackUrl == null) {
					requestToken = twitter.getOAuthRequestToken();
				} else {
					requestToken =
						twitter.getOAuthRequestToken(callbackUrl);
				}
				String authorisationUrl = requestToken
						.getAuthorizationURL();
				session.setAttribute(ATTR_TWITTER, twitter);
				session.setAttribute(ATTR_REQUEST_TOKEN, requestToken);

				logger.debug("Redirecting user to " + authorisationUrl);
				response.sendRedirect(authorisationUrl);
			} catch (TwitterException e) {
				logger.error("Sign in with Twitter failed - "
						+ e.getMessage());
				throw new ServletException(e);
			}
		}

	} else if (ACTION_UPDATE.equals(action)) {
	// Handle ACTION_UPDATE, ACTION_DELETE, ACTION_MORE and ACTION_LATEST
	......
}

protected void doPost(HttpServletRequest request,
		HttpServletResponse response) throws ServletException, IOException {
	HttpSession session = request.getSession();

	// OAuth authentication support
	......

	} else if (ACTION_UPDATE.equals(action)) {
		logger.debug("Updating Twitter status...");
		String status = request.getParameter(PARAM_STATUS);
		Twitter twitter = (Twitter) session.getAttribute(ATTR_TWITTER);
		try {
			Status twitterStatus = twitter.updateStatus(status);
			logger.debug("Successfully updated the status to ["
					+ twitterStatus.getText() + "].");
			// Update last status
			session.setAttribute(ATTR_LAST_UPDATED_STATUS, twitterStatus
					.getText()
					+ " " + twitterStatus.getCreatedAt());
			session.setAttribute(ATTR_LAST_UPDATED_STATUS_ID, ""
					+ twitterStatus.getId());

			// Update friends' timelines
			getFriendsTimelinesAndStoreInSession(session, true);

			// Stay in the update status page
			logger.debug("Staying in the status update page...");
			request.getRequestDispatcher(PAGE_UPDATE_STATUS).forward(
					request, response);
		} catch (TwitterException e) {
			logger.error("Failed to update Twitter status - "
					+ e.getMessage());
			throw new ServletException(e);
		}
	} else if (ACTION_DELETE.equals(action)) {
		logger.debug("Deleting Twitter status...");
		String strId = (String) session
				.getAttribute(ATTR_LAST_UPDATED_STATUS_ID);
		if (strId != null && strId != "") {
			Twitter twitter = (Twitter) session.getAttribute(ATTR_TWITTER);
			try {
				int id = twitter.verifyCredentials().getId();
				twitter.destroyStatus(Long.parseLong(strId));
				session.removeAttribute(ATTR_LAST_UPDATED_STATUS);
				session.removeAttribute(ATTR_LAST_UPDATED_STATUS_ID);
				logger.debug("Last update deleted for Twitter user " + id
						+ " deleted, session record removed");

				// Get last status and friends' timelines
				getMyLastStatusAndStoreInSession(session);
				getFriendsTimelinesAndStoreInSession(session, true);
			} catch (TwitterException e) {
				logger.error("Failed to delete Twitter status - "
						+ e.getMessage());
				throw new ServletException(e);
			}
		}

		// Stay in the update status page
		logger.debug("Staying in the status update page...");
		request.getRequestDispatcher(PAGE_UPDATE_STATUS).forward(request,
				response);
	} else if (ACTION_MORE.equals(action)) {
		// Update friends' timelines
		getFriendsTimelinesAndStoreInSession(session);

		// Stay in the update status page
		logger.debug("Staying in the status update page...");
		request.getRequestDispatcher(PAGE_UPDATE_STATUS).forward(request,
				response);
	} else if (ACTION_LATEST.equals(action)) {
		// Update friends' latest timelines
		getFriendsTimelinesAndStoreInSession(session, true);

		// Stay in the update status page
		logger.debug("Staying in the status update page...");
		request.getRequestDispatcher(PAGE_UPDATE_STATUS).forward(request,
				response);
	}
}