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.gdata.client.GData; import com.google.gwt.gdata.client.GDataSystemPackage; import com.google.gwt.gdata.client.impl.CallErrorException; import com.google.gwt.gdata.client.sidewiki.SidewikiAuthor; import com.google.gwt.gdata.client.sidewiki.SidewikiEntry; import com.google.gwt.gdata.client.sidewiki.SidewikiEntryFeed; import com.google.gwt.gdata.client.sidewiki.SidewikiEntryFeedCallback; import com.google.gwt.gdata.client.sidewiki.SidewikiEntryQuery; import com.google.gwt.gdata.client.sidewiki.SidewikiService; 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 query entries to find * Sidewiki entries by a given author. */ public class SidewikiQueryEntriesByAuthorDemo 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 SidewikiQueryEntriesByAuthorDemo(); } @Override public String getDescription() { return "<p>This sample uses an entry query to find Sidewiki content " + "by a given author.</p>"; } @Override public String getName() { return "Sidewiki - Querying entries by author"; } }; } private SidewikiService service; private FlexTable mainPanel; /** * Setup the Google Sidewiki service and create the main content panel. * Start the demo by querying Sidewiki entries. */ public SidewikiQueryEntriesByAuthorDemo() { mainPanel = new FlexTable(); initWidget(mainPanel); if (!GData.isLoaded(GDataSystemPackage.SIDEWIKI)) { showStatus("Loading the GData Sidewiki package...", false); GData.loadGDataApi(GDATA_API_KEY, new Runnable() { public void run() { startDemo(); } }, GDataSystemPackage.SIDEWIKI); } else { startDemo(); } } /** * Retrieves a Sidewiki entry feed using a Query object. * In GData, feed URIs can contain query string parameters. The * GData query objects aid in building parameterized feed URIs. * Upon successfully receiving the entries feed, we obtain the * first author of the first entry and query for Sidewiki entries * by that author. * * @param entriesFeedUri The items feed uri. */ private void queryEntries(String entriesFeedUri) { showStatus("Loading entries feed...", false); SidewikiEntryQuery query = SidewikiEntryQuery.newInstance(entriesFeedUri); query.setMaxResults(25); service.getSidewikiEntryFeed(query, new SidewikiEntryFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the entries feed: " + caught.getMessage(), true); } public void onSuccess(SidewikiEntryFeed result) { SidewikiEntry[] entries = result.getEntries(); if (entries.length == 0) { showStatus("No entries matched the search criteria.", false); } else { SidewikiAuthor author = (SidewikiAuthor) entries[0].getAuthors()[0]; queryEntriesByAuthor(author.getResourceId().getValue()); } } }); } /** * Retrieves a Sidewiki entry feed using a Query object. * In GData, feed URIs can contain query string parameters. The * GData query objects aid in building parameterized feed URIs. * Upon successfully receiving the entries feed, the entries * are displayed to the user via the showData method. * * @param entriesFeedUri The items feed uri. */ private void queryEntriesByAuthor(String authorId) { showStatus("Querying entries by author...", false); String feedUri = "http://www.google.com/sidewiki/feeds/entries/author/" + authorId + "/full"; SidewikiEntryQuery query = SidewikiEntryQuery.newInstance(feedUri); query.setMaxResults(25); service.getSidewikiEntryFeed(query, new SidewikiEntryFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the entries feed: " + caught.getMessage(), true); } public void onSuccess(SidewikiEntryFeed result) { SidewikiEntry[] entries = result.getEntries(); if (entries.length == 0) { showStatus("No entries matched the search criteria.", false); } else { showData(entries); } } }); } /** * Displays a set of Sidewiki entries in a tabular * fashion with the help of a GWT FlexTable widget. The data fields * Name and Url are displayed. * * @param entries The Sidewiki entries to display. */ private void showData(SidewikiEntry[] entries) { mainPanel.clear(); String[] labels = new String[] { "Name", "Url" }; 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++) { SidewikiEntry 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>")); } } } /** * 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 = SidewikiService.newInstance("HelloGData_Sidewiki_QueryEntriesByAuthorDemo_v2.0"); String webpageEncoded = "http%3A%2F%2Fwww.google.com%2F"; String webpageFeedUri = "http://www.google.com/sidewiki/feeds/entries/webpage/" + webpageEncoded + "/full"; queryEntries(webpageFeedUri); } }