org.opencastproject.mediapackage.MediaPackageElementBuilderImpl Maven / Gradle / Ivy
/*
* Licensed to The Apereo Foundation under one or more contributor license
* agreements. See the NOTICE file distributed with this work for additional
* information regarding copyright ownership.
*
*
* The Apereo Foundation licenses this file to you under the Educational
* Community 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://opensource.org/licenses/ecl2.txt
*
* 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 org.opencastproject.mediapackage;
import org.opencastproject.mediapackage.elementbuilder.AttachmentBuilderPlugin;
import org.opencastproject.mediapackage.elementbuilder.CatalogBuilderPlugin;
import org.opencastproject.mediapackage.elementbuilder.MediaPackageElementBuilderPlugin;
import org.opencastproject.mediapackage.elementbuilder.PublicationBuilderPlugin;
import org.opencastproject.mediapackage.elementbuilder.TrackBuilderPlugin;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Node;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
/**
* Default implementation for a media package element builder.
*/
public class MediaPackageElementBuilderImpl implements MediaPackageElementBuilder {
/** The list of plugins */
private List> plugins = null;
/** the logging facility provided by log4j */
private static final Logger logger = LoggerFactory.getLogger(MediaPackageElementBuilderImpl.class.getName());
// Create the list of available element builder pugins
public MediaPackageElementBuilderImpl() {
plugins = new ArrayList>();
plugins.add(AttachmentBuilderPlugin.class);
plugins.add(CatalogBuilderPlugin.class);
plugins.add(TrackBuilderPlugin.class);
plugins.add(PublicationBuilderPlugin.class);
}
/**
* @see org.opencastproject.mediapackage.MediaPackageElementBuilder#elementFromURI(URI)
*/
public MediaPackageElement elementFromURI(URI uri) throws UnsupportedElementException {
return elementFromURI(uri, null, null);
}
/**
* @see org.opencastproject.mediapackage.MediaPackageElementBuilder#elementFromURI(URI,
* org.opencastproject.mediapackage.MediaPackageElement.Type ,
* org.opencastproject.mediapackage.MediaPackageElementFlavor)
*/
public MediaPackageElement elementFromURI(URI uri, MediaPackageElement.Type type, MediaPackageElementFlavor flavor)
throws UnsupportedElementException {
// Feed the file to the element builder plugins
List candidates = new ArrayList();
{
MediaPackageElementBuilderPlugin plugin = null;
for (Class pluginClass : plugins) {
plugin = createPlugin(pluginClass);
if (plugin.accept(uri, type, flavor))
candidates.add(plugin);
}
}
// Check the plugins
if (candidates.size() == 0) {
throw new UnsupportedElementException("No suitable element builder plugin found for " + uri);
} else if (candidates.size() > 1) {
StringBuffer buf = new StringBuffer();
for (MediaPackageElementBuilderPlugin plugin : candidates) {
if (buf.length() > 0)
buf.append(", ");
buf.append(plugin.toString());
}
logger.debug("More than one element builder plugin with the same priority claims responsibilty for " + uri + ": "
+ buf.toString());
}
// Create media package element depending on mime type flavor
MediaPackageElementBuilderPlugin builderPlugin = candidates.get(0);
MediaPackageElement element = builderPlugin.elementFromURI(uri);
element.setFlavor(flavor);
builderPlugin.destroy();
return element;
}
/**
* @see org.opencastproject.mediapackage.MediaPackageElementBuilder#elementFromManifest(org.w3c.dom.Node,
* org.opencastproject.mediapackage.MediaPackageSerializer)
*/
public MediaPackageElement elementFromManifest(Node node, MediaPackageSerializer serializer)
throws UnsupportedElementException {
List candidates = new ArrayList();
for (Class pluginClass : plugins) {
MediaPackageElementBuilderPlugin plugin = createPlugin(pluginClass);
if (plugin.accept(node)) {
candidates.add(plugin);
}
}
// Check the plugins
if (candidates.size() == 0) {
throw new UnsupportedElementException("No suitable element builder plugin found for node " + node.getNodeName());
} else if (candidates.size() > 1) {
StringBuffer buf = new StringBuffer();
for (MediaPackageElementBuilderPlugin plugin : candidates) {
if (buf.length() > 0)
buf.append(", ");
buf.append(plugin.toString());
}
XPath xpath = XPathFactory.newInstance().newXPath();
String name = node.getNodeName();
String elementFlavor = null;
try {
elementFlavor = xpath.evaluate("@type", node);
} catch (XPathExpressionException e) {
elementFlavor = "(unknown)";
}
logger.debug("More than one element builder plugin claims responsability for " + name + " of flavor "
+ elementFlavor + ": " + buf.toString());
}
// Create a new media package element
MediaPackageElementBuilderPlugin builderPlugin = candidates.get(0);
MediaPackageElement element = builderPlugin.elementFromManifest(node, serializer);
builderPlugin.destroy();
return element;
}
/**
* @see org.opencastproject.mediapackage.MediaPackageElementBuilder#newElement(org.opencastproject.mediapackage.MediaPackageElement.Type
* , org.opencastproject.mediapackage.MediaPackageElementFlavor)
*/
public MediaPackageElement newElement(MediaPackageElement.Type type, MediaPackageElementFlavor flavor) {
List candidates = new ArrayList();
for (Class pluginClass : plugins) {
MediaPackageElementBuilderPlugin plugin = createPlugin(pluginClass);
if (plugin.accept(type, flavor)) {
candidates.add(plugin);
}
}
// Check the plugins
if (candidates.size() == 0)
return null;
else if (candidates.size() > 1) {
StringBuffer buf = new StringBuffer();
for (MediaPackageElementBuilderPlugin plugin : candidates) {
if (buf.length() > 0)
buf.append(", ");
buf.append(plugin.toString());
}
logger.debug("More than one element builder plugin claims responsibilty for " + flavor + ": " + buf.toString());
}
// Create a new media package element
MediaPackageElementBuilderPlugin builderPlugin = candidates.get(0);
MediaPackageElement element = builderPlugin.newElement(type, flavor);
builderPlugin.destroy();
return element;
}
/**
* Creates and initializes a new builder plugin.
*/
private MediaPackageElementBuilderPlugin createPlugin(Class clazz) {
MediaPackageElementBuilderPlugin plugin = null;
try {
plugin = clazz.newInstance();
} catch (InstantiationException e) {
throw new RuntimeException("Cannot instantiate media package element builder plugin of type " + clazz.getName()
+ ". Did you provide a parameterless constructor?", e);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
try {
plugin.init();
} catch (Exception e) {
throw new RuntimeException("An error occured while setting up media package element builder plugin " + plugin);
}
return plugin;
}
}