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.Category; import com.google.gwt.gdata.client.atom.Text; import com.google.gwt.gdata.client.blogger.BlogEntry; import com.google.gwt.gdata.client.blogger.BlogFeed; import com.google.gwt.gdata.client.blogger.BlogFeedCallback; import com.google.gwt.gdata.client.blogger.BlogPostFeed; import com.google.gwt.gdata.client.blogger.BlogPostFeedCallback; import com.google.gwt.gdata.client.blogger.BloggerService; import com.google.gwt.gdata.client.blogger.PostEntry; import com.google.gwt.gdata.client.blogger.PostEntryCallback; 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 a blog post. */ public class BloggerUpdateBlogPostDemo 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 BloggerUpdateBlogPostDemo(); } @Override public String getDescription() { return "<p>This sample updates the first blog post it finds that " + "begins with the prefix 'GWT-Blogger-Client'.</p>"; } @Override public String getName() { return "Blogger - Updating a blog post"; } }; } private BloggerService service; private FlexTable mainPanel; private final String scope = "http://www.blogger.com/feeds/"; /** * Setup the Blogger service and create the main content panel. * If the user is not logged on to Blogger display a message, * otherwise start the demo by retrieving the user's blogs. */ public BloggerUpdateBlogPostDemo() { mainPanel = new FlexTable(); initWidget(mainPanel); if (!GData.isLoaded(GDataSystemPackage.BLOGGER)) { showStatus("Loading the GData Blogger package...", false); GData.loadGDataApi(GDATA_API_KEY, new Runnable() { public void run() { startDemo(); } }, GDataSystemPackage.BLOGGER); } else { startDemo(); } } /** * Retrieve the Blogger blogs feed using the Blogger service and * the blogs 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 Blog entry and * calls getPosts to retrieve the posts feed for that blog. * * @param blogsFeedUri The uri of the blogs feed */ private void getBlogs(String blogsFeedUri) { showStatus("Loading blog feed...", false); service.getBlogFeed(blogsFeedUri, new BlogFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the Blogger Blog " + "feed: " + caught.getMessage(), true); } public void onSuccess(BlogFeed result) { BlogEntry[] entries = result.getEntries(); if (entries.length == 0) { showStatus("You have no Blogger blogs.", false); } else { BlogEntry targetBlog = entries[0]; String postsFeedUri = targetBlog.getEntryPostLink().getHref(); getPosts(postsFeedUri); } } }); } /** * Retrieve the Blogger posts feed using the Blogger service and * the posts feed uri for a given blog. * On success, identify the first post entry with a title starting * with "GWT-Blogger-Client", this will be the post that will be updated. * If no post is found, display a message. * Otherwise call updatePost to update the post. * * @param postsFeedUri The posts feed uri for a given blog */ private void getPosts(String postsFeedUri) { showStatus("Loading posts feed...", false); service.getBlogPostFeed(postsFeedUri, new BlogPostFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the Blogger Posts " + "feed: " + caught.getMessage(), true); } public void onSuccess(BlogPostFeed result) { PostEntry targetPost = null; for (PostEntry entry : result.getEntries()) { String title = entry.getTitle().getText(); if (title.startsWith("GWT-Blogger-Client")) { targetPost = entry; break; } } if (targetPost == null) { showStatus("Did not find a post entry whose title starts with " + "the prefix 'GWT-Blogger-Client'.", false); } else { updatePost(targetPost); } } }); } /** * 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 = BloggerService.newInstance("HelloGData_Blogger_UpdateBlogPostDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Update a blog post"); startButton.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { getBlogs("http://www.blogger.com/feeds/default/blogs"); } }); mainPanel.setWidget(0, 0, startButton); } else { showStatus("You are not logged on to Blogger.", true); } } /** * Update a blog post by making use of the updateEntry * method of the Entry class. * Set the post's title and contents to an arbitrary string. Here * we prefix the title with 'GWT-Blogger-Client' so that * we can identify which posts were updated by this demo. * We also update the name of one of the post's categories. * On success and failure, display a status message. * * @param postEntry The post entry which to update */ private void updatePost(PostEntry postEntry) { showStatus("Updating post entry...", false); postEntry.getTitle().setText("GWT-Blogger-Client - updated post"); postEntry.setContent(Text.newInstance()); postEntry.getContent().setText("My updated post"); Category[] categories = postEntry.getCategories(); for (Category category : categories) { if (category.getTerm().equals("Label1")) { category.setTerm("Label1-updated"); } } postEntry.updateEntry(new PostEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while updating a blog post: " + caught.getMessage(), true); } public void onSuccess(PostEntry result) { showStatus("Updated a blog entry.", false); } }); } }