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.DateTime; import com.google.gwt.gdata.client.GData; import com.google.gwt.gdata.client.GDataRequestParameters; import com.google.gwt.gdata.client.GDataSystemPackage; import com.google.gwt.gdata.client.contacts.ContactEntry; import com.google.gwt.gdata.client.contacts.ContactEntryCallback; import com.google.gwt.gdata.client.contacts.ContactFeed; import com.google.gwt.gdata.client.contacts.ContactFeedCallback; import com.google.gwt.gdata.client.contacts.ContactQuery; import com.google.gwt.gdata.client.contacts.ContactsService; 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; import java.util.Date; /** * The following example demonstrates how to delete a contact. */ public class ContactsDeleteContactDemo 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 ContactsDeleteContactDemo(); } @Override public String getDescription() { return "<p>This sample demonstrates how to delete a contact " + "entry. It queries for the most recently modified contact " + "entry and deletes it.</p>"; } @Override public String getName() { return "Contacts - Deleting contacts"; } }; } private ContactsService service; private FlexTable mainPanel; private final String scope = "http://www.google.com/m8/feeds/"; /** * Setup the Contacts service and create the main content panel. * If the user is not logged on to Contacts display a message, * otherwise start the demo by querying the user's contacts. */ public ContactsDeleteContactDemo() { mainPanel = new FlexTable(); initWidget(mainPanel); if (!GData.isLoaded(GDataSystemPackage.CONTACTS)) { showStatus("Loading the GData Contacts package...", false); GData.loadGDataApi(GDATA_API_KEY, new Runnable() { public void run() { startDemo(); } }, GDataSystemPackage.CONTACTS); } else { startDemo(); } } /** * Delete a contact entry using the Contact service and * the contact entry uri. * On success and failure, display a status message. * * @param contactEntryUri The uri of the contact entry to delete * @param etag The etag of the entry to be deleted */ private void deleteContact(String contactEntryUri, String etag) { showStatus("Deleting a contact...", false); GDataRequestParameters pars = GDataRequestParameters.newInstance(); pars.setEtag(etag); service.deleteEntry(contactEntryUri, new ContactEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while deleting a contact: " + caught.getMessage(), true); } public void onSuccess(ContactEntry result) { showStatus("Deleted a contact.", false); } }, pars); } /** * Retrieves a contacts feed using a Query object. * In GData, feed URIs can contain query string parameters. The * GData query objects aid in building parameterized feed URIs. * On success, obtain the first contact entry with a title starting * with "GWT-Contacts-Client", this is the contact that will be deleted. * If no contact is found, display a message. * Otherwise call deleteContact to delete the contact entry. * Alternatively we could also have used targetContact.deleteEntry to * delete the contact, but the effect is the same. * * @param contactsFeedUri The contacts feed uri. */ private void queryContacts(String contactsFeedUri) { showStatus("Querying contacts...", false); ContactQuery query = ContactQuery.newInstance(contactsFeedUri); Date today = new Date(); DateTime updatedMin = DateTime.newInstance(today, true); query.setUpdatedMin(updatedMin); query.setSortOrder(ContactQuery.SORTORDER_DESCENDING); service.getContactFeed(query, new ContactFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the Contacts feed: " + caught.getMessage(), true); } public void onSuccess(ContactFeed result) { ContactEntry[] entries = result.getEntries(); ContactEntry targetContact = null; for (ContactEntry contact : entries) { String title = contact.getTitle().getText(); if (title.startsWith("GWT-Contacts-Client")) { targetContact = contact; break; } } if (targetContact == null) { showStatus("No contacts were found that were modified today and " + "contained 'GWT-Contacts-Client' in the title.", false); } else { String contactEntryUri = targetContact.getEditLink().getHref(); deleteContact(contactEntryUri, targetContact.getEtag()); } } }); } /** * 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 = ContactsService.newInstance("HelloGData_Contacts_DeleteContactDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Delete a contact"); startButton.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { queryContacts("http://www.google.com/m8/feeds/contacts/default/full"); } }); mainPanel.setWidget(0, 0, startButton); } else { showStatus("You are not logged on to Google Contacts.", true); } } }