Java tutorial
/* * Copyright 2008 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.gdata.sample.hellogdata.client; import com.google.gwt.accounts.client.AuthSubStatus; import com.google.gwt.accounts.client.User; import com.google.gwt.gdata.client.GData; import com.google.gwt.gdata.client.GDataSystemPackage; import com.google.gwt.gdata.client.gbase.GoogleBaseService; import com.google.gwt.gdata.client.gbase.ItemsEntry; import com.google.gwt.gdata.client.gbase.ItemsFeed; import com.google.gwt.gdata.client.gbase.ItemsFeedCallback; import com.google.gwt.gdata.client.impl.CallErrorException; import com.google.gwt.user.client.ui.FlexTable; import com.google.gwt.user.client.ui.HTML; import com.google.gwt.user.client.ui.Label; /** * The following example demonstrates how to retrieve a list of a user's items. */ public class GoogleBaseRetrieveItemsDemo extends GDataDemo { /** * This method is used by the main sample app to obtain * information on this sample and a sample instance. * * @return An instance of this demo. */ public static GDataDemoInfo init() { return new GDataDemoInfo() { @Override public GDataDemo createInstance() { return new GoogleBaseRetrieveItemsDemo(); } @Override public String getDescription() { return "<p>This sample uses the items feed to retrieve a list " + "of all of an authenticated user's items. The title and URL of " + "each item entry is printed.</p>"; } @Override public String getName() { return "Base - Retrieving all items"; } }; } private GoogleBaseService service; private FlexTable mainPanel; private final String scope = "http://www.google.com/base/feeds/"; /** * Setup the Google Base service and create the main content panel. * If the user is not logged on to Google Base display a message, * otherwise start the demo by retrieving the user's items. */ public GoogleBaseRetrieveItemsDemo() { mainPanel = new FlexTable(); initWidget(mainPanel); if (!GData.isLoaded(GDataSystemPackage.GBASE)) { showStatus("Loading the GData Google-Base package...", false); GData.loadGDataApi(GDATA_API_KEY, new Runnable() { public void run() { startDemo(); } }, GDataSystemPackage.GBASE); } else { startDemo(); } } /** * Retrieve the items feed using the Google Base service and * the items feed uri. In GData all get, insert, update * and delete methods always receive a callback defining success * and failure handlers. * Here, the failure handler displays an error message while the * success handler calls showData to display the item entries. * * @param itemsFeedUri The uri of the items feed */ private void getItems(String itemsFeedUri) { showStatus("Loading items feed...", false); service.getItemsFeed(itemsFeedUri, new ItemsFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the items feed: " + caught.getMessage(), true); } public void onSuccess(ItemsFeed result) { ItemsEntry[] entries = result.getEntries(); if (entries.length == 0) { showStatus("You have no items.", false); } else { showData(entries); } } }); } /** * Displays a set of Google Base item entries in a tabular * fashion with the help of a GWT FlexTable widget. The data fields * Title, URL and Published are displayed. * * @param entries The Google Base item entries to display. */ private void showData(ItemsEntry[] entries) { mainPanel.clear(); String[] labels = new String[] { "Title", "URL", "Published" }; mainPanel.insertRow(0); for (int i = 0; i < labels.length; i++) { mainPanel.addCell(0); mainPanel.setWidget(0, i, new Label(labels[i])); mainPanel.getFlexCellFormatter().setStyleName(0, i, "hm-tableheader"); } for (int i = 0; i < entries.length; i++) { ItemsEntry entry = entries[i]; int row = mainPanel.insertRow(i + 1); mainPanel.addCell(row); mainPanel.setWidget(row, 0, new Label(entry.getTitle().getText())); mainPanel.addCell(row); if (entry.getHtmlLink() == null) { mainPanel.setWidget(row, 1, new Label("Not available")); } else { String link = entry.getHtmlLink().getHref(); mainPanel.setWidget(row, 1, new HTML("<a href=\"" + link + "\" target=\"_blank\">" + link + "</a>")); mainPanel.addCell(row); mainPanel.setWidget(row, 2, new Label(entry.getPublished().getValue().getDate().toString())); } } } /** * Displays a status message to the user. * * @param message The message to display. * @param isError Indicates whether the status is an error status. */ private void showStatus(String message, boolean isError) { mainPanel.clear(); mainPanel.insertRow(0); mainPanel.addCell(0); Label msg = new Label(message); if (isError) { msg.setStylePrimaryName("hm-error"); } mainPanel.setWidget(0, 0, msg); } /** * Starts this demo. */ private void startDemo() { service = GoogleBaseService.newInstance("HelloGData_GoogleBase_RetrieveItemsDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { getItems("http://www.google.com/base/feeds/items"); } else { showStatus("You are not logged on to Google Base.", true); } } }