Java tutorial
/** * The contents of this file are subject to the license and copyright * detailed in the LICENSE and NOTICE files at the root of the source * tree and available online at * * http://www.dspace.org/license/ */ package org.dspace.app.util; import java.io.IOException; import java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.Map; import javax.servlet.http.HttpServletRequest; import org.apache.commons.lang.ArrayUtils; import org.apache.commons.lang.StringUtils; import org.w3c.dom.Document; import org.dspace.content.Bitstream; import org.dspace.content.Collection; import org.dspace.content.Community; import org.dspace.content.DCDate; import org.dspace.content.DCValue; import org.dspace.content.DSpaceObject; import org.dspace.content.Item; import org.dspace.core.ConfigurationManager; import org.dspace.core.Constants; import org.dspace.handle.HandleManager; import com.sun.syndication.feed.synd.SyndFeed; import com.sun.syndication.feed.synd.SyndFeedImpl; import com.sun.syndication.feed.synd.SyndEntry; import com.sun.syndication.feed.synd.SyndEntryImpl; import com.sun.syndication.feed.synd.SyndEnclosure; import com.sun.syndication.feed.synd.SyndEnclosureImpl; import com.sun.syndication.feed.synd.SyndImage; import com.sun.syndication.feed.synd.SyndImageImpl; import com.sun.syndication.feed.synd.SyndPerson; import com.sun.syndication.feed.synd.SyndPersonImpl; import com.sun.syndication.feed.synd.SyndContent; import com.sun.syndication.feed.synd.SyndContentImpl; import com.sun.syndication.feed.module.DCModuleImpl; import com.sun.syndication.feed.module.DCModule; import com.sun.syndication.feed.module.Module; import com.sun.syndication.feed.module.itunes.*; import com.sun.syndication.feed.module.itunes.types.Duration; import com.sun.syndication.io.SyndFeedOutput; import com.sun.syndication.io.FeedException; import org.apache.log4j.Logger; import org.dspace.content.Bundle; /** * Invoke ROME library to assemble a generic model of a syndication * for the given list of Items and scope. Consults configuration for the * metadata bindings to feed elements. Uses ROME's output drivers to * return any of the implemented formats, e.g. RSS 1.0, RSS 2.0, ATOM 1.0. * * The feed generator and OpenSearch call on this class so feed contents are * uniform for both. * * @author Larry Stone */ public class SyndicationFeed { private static final Logger log = Logger.getLogger(SyndicationFeed.class); /** i18n key values */ public static final String MSG_UNTITLED = "notitle"; public static final String MSG_LOGO_TITLE = "logo.title"; public static final String MSG_FEED_TITLE = "feed.title"; public static final String MSG_FEED_DESCRIPTION = "general-feed.description"; public static final String MSG_METADATA = "metadata."; public static final String MSG_UITYPE = "ui.type"; // UI keywords public static final String UITYPE_XMLUI = "xmlui"; public static final String UITYPE_JSPUI = "jspui"; // default DC fields for entry private static String defaultTitleField = "dc.title"; private static String defaultAuthorField = "dc.contributor.author"; private static String defaultDateField = "dc.date.issued"; private static String defaultDescriptionFields = "dc.description.abstract, dc.description, dc.title.alternative, dc.title"; private static String defaultExternalMedia = "dc.source.uri"; // metadata field for Item title in entry: private static String titleField = getDefaultedConfiguration("webui.feed.item.title", defaultTitleField); // metadata field for Item publication date in entry: private static String dateField = getDefaultedConfiguration("webui.feed.item.date", defaultDateField); // metadata field for Item description in entry: private static String descriptionFields[] = getDefaultedConfiguration("webui.feed.item.description", defaultDescriptionFields).split("\\s*,\\s*"); private static String authorField = getDefaultedConfiguration("webui.feed.item.author", defaultAuthorField); // metadata field for Podcast external media source url private static String externalSourceField = getDefaultedConfiguration("webui.feed.podcast.sourceuri", defaultExternalMedia); // metadata field for Item dc:creator field in entry's DCModule (no default) private static String dcCreatorField = ConfigurationManager.getProperty("webui.feed.item.dc.creator"); // metadata field for Item dc:date field in entry's DCModule (no default) private static String dcDateField = ConfigurationManager.getProperty("webui.feed.item.dc.date"); // metadata field for Item dc:author field in entry's DCModule (no default) private static String dcDescriptionField = ConfigurationManager.getProperty("webui.feed.item.dc.description"); // List of available mimetypes that we'll add to podcast feed. Multiple values separated by commas private static String podcastableMIMETypes = getDefaultedConfiguration("webui.feed.podcast.mimetypes", "audio/x-mpeg"); // -------- Instance variables: // the feed object we are building private SyndFeed feed = null; // memory of UI that called us, "xmlui" or "jspui" // affects Bitstream retrieval URL and I18N keys private String uiType = null; private HttpServletRequest request = null; /** * Constructor. * @param ui either "xmlui" or "jspui" */ public SyndicationFeed(String ui) { feed = new SyndFeedImpl(); uiType = ui; } /** * Returns list of metadata selectors used to compose the description element * * @return selector list - format 'schema.element[.qualifier]' */ public static String[] getDescriptionSelectors() { return (String[]) ArrayUtils.clone(descriptionFields); } /** * Fills in the feed and entry-level metadata from DSpace objects. */ public void populate(HttpServletRequest request, DSpaceObject dso, DSpaceObject items[], Map<String, String> labels) { String logoURL = null; String objectURL = null; String defaultTitle = null; boolean podcastFeed = false; this.request = request; // dso is null for the whole site, or a search without scope if (dso == null) { defaultTitle = ConfigurationManager.getProperty("dspace.name"); feed.setDescription(localize(labels, MSG_FEED_DESCRIPTION)); objectURL = resolveURL(request, null); logoURL = ConfigurationManager.getProperty("webui.feed.logo.url"); } else { Bitstream logo = null; if (dso.getType() == Constants.COLLECTION) { Collection col = (Collection) dso; defaultTitle = col.getMetadata("name"); feed.setDescription(col.getMetadata("short_description")); logo = col.getLogo(); String cols = ConfigurationManager.getProperty("webui.feed.podcast.collections"); if (cols != null && cols.length() > 1 && cols.contains(col.getHandle())) { podcastFeed = true; } } else if (dso.getType() == Constants.COMMUNITY) { Community comm = (Community) dso; defaultTitle = comm.getMetadata("name"); feed.setDescription(comm.getMetadata("short_description")); logo = comm.getLogo(); String comms = ConfigurationManager.getProperty("webui.feed.podcast.communities"); if (comms != null && comms.length() > 1 && comms.contains(comm.getHandle())) { podcastFeed = true; } } objectURL = resolveURL(request, dso); if (logo != null) { logoURL = urlOfBitstream(request, logo); } } feed.setTitle(labels.containsKey(MSG_FEED_TITLE) ? localize(labels, MSG_FEED_TITLE) : defaultTitle); feed.setLink(objectURL); feed.setPublishedDate(new Date()); feed.setUri(objectURL); // add logo if we found one: if (logoURL != null) { // we use the path to the logo for this, the logo itself cannot // be contained in the rdf. Not all RSS-viewers show this logo. SyndImage image = new SyndImageImpl(); image.setLink(objectURL); if (StringUtils.isNotBlank(feed.getTitle())) { image.setTitle(feed.getTitle()); } else { image.setTitle(localize(labels, MSG_LOGO_TITLE)); } image.setUrl(logoURL); feed.setImage(image); } // add entries for items if (items != null) { List<SyndEntry> entries = new ArrayList<SyndEntry>(); for (DSpaceObject itemDSO : items) { if (itemDSO.getType() != Constants.ITEM) { continue; } Item item = (Item) itemDSO; boolean hasDate = false; SyndEntry entry = new SyndEntryImpl(); entries.add(entry); String entryURL = resolveURL(request, item); entry.setLink(entryURL); entry.setUri(entryURL); String title = getOneDC(item, titleField); entry.setTitle(title == null ? localize(labels, MSG_UNTITLED) : title); // "published" date -- should be dc.date.issued String pubDate = getOneDC(item, dateField); if (pubDate != null) { entry.setPublishedDate((new DCDate(pubDate)).toDate()); hasDate = true; } // date of last change to Item entry.setUpdatedDate(item.getLastModified()); StringBuffer db = new StringBuffer(); for (String df : descriptionFields) { // Special Case: "(date)" in field name means render as date boolean isDate = df.indexOf("(date)") > 0; if (isDate) { df = df.replaceAll("\\(date\\)", ""); } DCValue dcv[] = item.getMetadata(df); if (dcv.length > 0) { String fieldLabel = labels.get(MSG_METADATA + df); if (fieldLabel != null && fieldLabel.length() > 0) { db.append(fieldLabel).append(": "); } boolean first = true; for (DCValue v : dcv) { if (first) { first = false; } else { db.append("; "); } db.append(isDate ? new DCDate(v.value).toString() : v.value); } db.append("\n"); } } if (db.length() > 0) { SyndContent desc = new SyndContentImpl(); desc.setType("text/plain"); desc.setValue(db.toString()); entry.setDescription(desc); } // This gets the authors into an ATOM feed DCValue authors[] = item.getMetadata(authorField); if (authors.length > 0) { List<SyndPerson> creators = new ArrayList<SyndPerson>(); for (DCValue author : authors) { SyndPerson sp = new SyndPersonImpl(); sp.setName(author.value); creators.add(sp); } entry.setAuthors(creators); } // only add DC module if any DC fields are configured if (dcCreatorField != null || dcDateField != null || dcDescriptionField != null) { DCModule dc = new DCModuleImpl(); if (dcCreatorField != null) { DCValue dcAuthors[] = item.getMetadata(dcCreatorField); if (dcAuthors.length > 0) { List<String> creators = new ArrayList<String>(); for (DCValue author : dcAuthors) { creators.add(author.value); } dc.setCreators(creators); } } if (dcDateField != null && !hasDate) { DCValue v[] = item.getMetadata(dcDateField); if (v.length > 0) { dc.setDate((new DCDate(v[0].value)).toDate()); } } if (dcDescriptionField != null) { DCValue v[] = item.getMetadata(dcDescriptionField); if (v.length > 0) { StringBuffer descs = new StringBuffer(); for (DCValue d : v) { if (descs.length() > 0) { descs.append("\n\n"); } descs.append(d.value); } dc.setDescription(descs.toString()); } } entry.getModules().add(dc); } //iTunes Podcast Support - START if (podcastFeed) { // Add enclosure(s) List<SyndEnclosure> enclosures = new ArrayList(); try { Bundle[] bunds = item.getBundles("ORIGINAL"); if (bunds[0] != null) { Bitstream[] bits = bunds[0].getBitstreams(); for (int i = 0; (i < bits.length); i++) { String mime = bits[i].getFormat().getMIMEType(); if (podcastableMIMETypes.contains(mime)) { SyndEnclosure enc = new SyndEnclosureImpl(); enc.setType(bits[i].getFormat().getMIMEType()); enc.setLength(bits[i].getSize()); enc.setUrl(urlOfBitstream(request, bits[i])); enclosures.add(enc); } else { continue; } } } //Also try to add an external value from dc.identifier.other // We are assuming that if this is set, then it is a media file DCValue[] externalMedia = item.getMetadata(externalSourceField); if (externalMedia.length > 0) { for (int i = 0; i < externalMedia.length; i++) { SyndEnclosure enc = new SyndEnclosureImpl(); enc.setType("audio/x-mpeg"); //We can't determine MIME of external file, so just picking one. enc.setLength(1); enc.setUrl(externalMedia[i].value); enclosures.add(enc); } } } catch (Exception e) { System.out.println(e.getMessage()); } entry.setEnclosures(enclosures); // Get iTunes specific fields: author, subtitle, summary, duration, keywords EntryInformation itunes = new EntryInformationImpl(); String author = getOneDC(item, authorField); if (author != null && author.length() > 0) { itunes.setAuthor(author); // <itunes:author> } itunes.setSubtitle(title == null ? localize(labels, MSG_UNTITLED) : title); // <itunes:subtitle> if (db.length() > 0) { itunes.setSummary(db.toString()); // <itunes:summary> } String extent = getOneDC(item, "dc.format.extent"); // assumed that user will enter this field with length of song in seconds if (extent != null && extent.length() > 0) { extent = extent.split(" ")[0]; Integer duration = Integer.parseInt(extent); itunes.setDuration(new Duration(duration)); // <itunes:duration> } String subject = getOneDC(item, "dc.subject"); if (subject != null && subject.length() > 0) { String[] subjects = new String[1]; subjects[0] = subject; itunes.setKeywords(subjects); // <itunes:keywords> } entry.getModules().add(itunes); } } feed.setEntries(entries); } } /** * Sets the feed type for XML delivery, e.g. "rss_1.0", "atom_1.0" * Must match one of ROME's configured generators, see rome.properties * (currently rss_1.0, rss_2.0, atom_1.0, atom_0.3) */ public void setType(String feedType) { feed.setFeedType(feedType); // XXX FIXME: workaround ROME 1.0 bug, it puts invalid image element in rss1.0 if ("rss_1.0".equals(feedType)) { feed.setImage(null); } } /** * @return the feed we built as DOM Document */ public Document outputW3CDom() throws FeedException { try { SyndFeedOutput feedWriter = new SyndFeedOutput(); return feedWriter.outputW3CDom(feed); } catch (FeedException e) { log.error(e); throw e; } } /** * @return the feed we built as serialized XML string */ public String outputString() throws FeedException { SyndFeedOutput feedWriter = new SyndFeedOutput(); return feedWriter.outputString(feed); } /** * send the output to designated Writer */ public void output(java.io.Writer writer) throws FeedException, IOException { SyndFeedOutput feedWriter = new SyndFeedOutput(); feedWriter.output(feed, writer); } /** * Add a ROME plugin module (e.g. for OpenSearch) at the feed level. */ public void addModule(Module m) { feed.getModules().add(m); } // utility to get config property with default value when not set. private static String getDefaultedConfiguration(String key, String dfl) { String result = ConfigurationManager.getProperty(key); return (result == null) ? dfl : result; } // returns absolute URL to download content of bitstream (which might not belong to any Item) private String urlOfBitstream(HttpServletRequest request, Bitstream logo) { String name = logo.getName(); return resolveURL(request, null) + (uiType.equalsIgnoreCase(UITYPE_XMLUI) ? "/bitstream/id/" : "/retrieve/") + logo.getID() + "/" + (name == null ? "" : name); } /** * Return a url to the DSpace object, either use the official * handle for the item or build a url based upon the current server. * * If the dspaceobject is null then a local url to the repository is generated. * * @param dso The object to reference, null if to the repository. * @return */ private String baseURL = null; // cache the result for null private String resolveURL(HttpServletRequest request, DSpaceObject dso) { // If no object given then just link to the whole repository, // since no offical handle exists so we have to use local resolution. if (dso == null) { if (baseURL == null) { if (request == null) { baseURL = ConfigurationManager.getProperty("dspace.url"); } else { baseURL = (request.isSecure()) ? "https://" : "http://"; baseURL += ConfigurationManager.getProperty("dspace.hostname"); baseURL += ":" + request.getServerPort(); baseURL += request.getContextPath(); } } return baseURL; } // return a link to handle in repository else if (ConfigurationManager.getBooleanProperty("webui.feed.localresolve")) { return resolveURL(request, null) + "/handle/" + dso.getHandle(); } // link to the Handle server or other persistent URL source else { return HandleManager.getCanonicalForm(dso.getHandle()); } } // retrieve text for localization key, or mark untranslated private String localize(Map<String, String> labels, String s) { return labels.containsKey(s) ? labels.get(s) : ("Untranslated:" + s); } // spoonful of syntactic sugar when we only need first value private String getOneDC(Item item, String field) { DCValue dcv[] = item.getMetadata(field); return (dcv.length > 0) ? dcv[0].value : null; } }