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.event.dom.client.ClickEvent; import com.google.gwt.event.dom.client.ClickHandler; import com.google.gwt.gdata.client.GData; import com.google.gwt.gdata.client.GDataSystemPackage; import com.google.gwt.gdata.client.atom.Text; import com.google.gwt.gdata.client.gbase.GoogleBaseService; import com.google.gwt.gdata.client.gbase.ItemsEntry; import com.google.gwt.gdata.client.gbase.ItemsEntryCallback; import com.google.gwt.gdata.client.gbase.ItemsFeed; import com.google.gwt.gdata.client.gbase.ItemsFeedCallback; import com.google.gwt.gdata.client.gbase.MapAttribute; import com.google.gwt.gdata.client.impl.CallErrorException; import com.google.gwt.user.client.ui.Button; import com.google.gwt.user.client.ui.FlexTable; import com.google.gwt.user.client.ui.Label; /** * The following example demonstrates how to update an item. */ public class GoogleBaseUpdateItemDemo 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 GoogleBaseUpdateItemDemo(); } @Override public String getDescription() { return "<p>This sample code demonstrates how to update an existing " + "item of the authenticated user. It retrieves a list of the " + "user's items, and updates the first item with a title that " + "starts with 'GWT-GoogleBase-Client' with a new title and " + "target country.</p>"; } @Override public String getName() { return "Base - Updating an item"; } }; } 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 GoogleBaseUpdateItemDemo() { 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 obtains the first Item entry with a title * starting with "GWT-GoogleBase-Client" and calls updateItem * to update the item. * If no item is found a message is displayed. * * @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(); ItemsEntry targetEntry = null; for (ItemsEntry entry : entries) { if (entry.getTitle().getText().startsWith("GWT-GoogleBase-Client")) { targetEntry = entry; break; } } if (targetEntry == null) { showStatus("No item found that contains 'GWT-GoogleBase-Client' " + "in the title.", false); } else { updateItem(targetEntry); } } }); } /** * 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_UpdateItemDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Update an item"); startButton.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { getItems("http://www.google.com/base/feeds/items/"); } }); mainPanel.setWidget(0, 0, startButton); } else { showStatus("You are not logged on to Google Base.", true); } } /** * Update an item by making use of the updateEntry * method of the Entry class. * Set the item's title to an arbitrary string. Here * we prefix the title with 'GWT-GoogleBase-Client' so that * we can identify which items were updated by this demo. * We also update the target_country property for this item. * On success and failure, display a status message. * * @param itemsEntry The item entry which to update */ private void updateItem(ItemsEntry itemsEntry) { showStatus("Updating item...", false); itemsEntry.setTitle(Text.newInstance()); itemsEntry.getTitle().setText("GWT-GoogleBase-Client - updated item"); MapAttribute attributes = itemsEntry.getAttributes(); if (attributes.contains("target_country")) { attributes.get("target_country")[0].setValue("UK"); } itemsEntry.updateEntry(new ItemsEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while updating an item: " + caught.getMessage(), true); } public void onSuccess(ItemsEntry result) { showStatus("Updated an item.", false); } }); } }