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.blogger.BlogCommentFeed; import com.google.gwt.gdata.client.blogger.BlogCommentFeedCallback; 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.CommentEntry; import com.google.gwt.gdata.client.blogger.CommentEntryCallback; import com.google.gwt.gdata.client.blogger.PostEntry; 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 delete a blog post comment. */ public class BloggerDeleteBlogPostCommentDemo 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 BloggerDeleteBlogPostCommentDemo(); } @Override public String getDescription() { return "<p>This sample deletes a comment from a blog post.</p>"; } @Override public String getName() { return "Blogger - Deleting a comment"; } }; } 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 BloggerDeleteBlogPostCommentDemo() { 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(); } } /** * Delete a comment entry using the Blogger service and * the comment entry uri. * On success and failure, display a status message. * * @param commentEntryUri The uri of the comment entry to delete */ private void deleteComment(String commentEntryUri) { showStatus("Deleting comment entry...", false); service.deleteEntry(commentEntryUri, new CommentEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while deleting a Blogger blog " + "comment: " + caught.getMessage(), true); } public void onSuccess(CommentEntry result) { showStatus("Deleted a comment.", false); } }); } /** * 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 comments feed using the Blogger service and * the comments feed uri for a given post. * On success, identify the first comment entry with a title starting * with "GWT-Blogger-Client", this will be the comment that will be deleted. * If no comment is found, display a message. * Otherwise call deleteComment to delete the comment. Alternatively * we could also have used targetComment.deleteEntry to * delete the comment, but the effect is the same. * * @param commentsFeedUri The comments feed uri for a given post */ private void getComments(String commentsFeedUri) { showStatus("Loading Blogger post comments feed...", false); service.getBlogCommentFeed(commentsFeedUri, new BlogCommentFeedCallback() { public void onFailure(CallErrorException caught) { showStatus( "An error occurred while retrieving the Blogger Comments " + "feed: " + caught.getMessage(), true); } public void onSuccess(BlogCommentFeed result) { if (result.getEntries().length == 0) { showStatus("The target blog post has no comments.", false); } else { // get the first comment that matches CommentEntry targetComment = null; for (CommentEntry comment : result.getEntries()) { String title = comment.getTitle().getText(); if (title.startsWith("GWT-Blogger-Client")) { targetComment = comment; break; } } if (targetComment == null) { showStatus("Did not find a comment entry whose title starts " + "with the prefix 'GWT-Blogger-Client'.", false); } else { deleteComment(targetComment.getSelfLink().getHref()); } } } }); } /** * 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 that is available * for commenting, this will be the post entry for which a comment * will be deleted. * If no posts are available for commenting, display a message. * Otherwise call getComments to retrieve the comments feed * for the target 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; // get the first public post for (PostEntry post : result.getEntries()) { if (post.getRepliesLink() != null) { targetPost = post; break; } } if (targetPost == null) { showStatus("The target blog contains no public posts.", false); } else { String commentsFeedUri = targetPost.getRepliesLink().getHref(); getComments(commentsFeedUri); } } }); } /** * 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_DeleteBlogPostCommentDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Delete a blog comment"); 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); } } }