PhotoCollectionProviderSupport.java
/*
* *********************************************************************************************************************
*
* blueMarine II: Semantic Media Centre
* http://tidalwave.it/projects/bluemarine2
*
* Copyright (C) 2015 - 2021 by Tidalwave s.a.s. (http://tidalwave.it)
*
* *********************************************************************************************************************
*
* 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.
*
* *********************************************************************************************************************
*
* git clone https://bitbucket.org/tidalwave/bluemarine2-src
* git clone https://github.com/tidalwave-it/bluemarine2-src
*
* *********************************************************************************************************************
*/
package it.tidalwave.bluemarine2.service.stoppingdown.impl;
import javax.annotation.Nonnull;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.ConcurrentHashMap;
import java.util.Map;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;
import java.io.IOException;
import it.tidalwave.util.annotation.VisibleForTesting;
import org.w3c.dom.Document;
import org.w3c.dom.DOMException;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import org.springframework.scheduling.annotation.Scheduled;
import it.tidalwave.bluemarine2.model.MediaFolder;
import it.tidalwave.bluemarine2.model.spi.PathAwareEntity;
import it.tidalwave.bluemarine2.model.spi.PathAwareFinder;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
/***********************************************************************************************************************
*
* @author Fabrizio Giudici
*
**********************************************************************************************************************/
@RequiredArgsConstructor @Slf4j
public class PhotoCollectionProviderSupport implements PhotoCollectionProvider
{
protected static final String URL_STOPPINGDOWN = System.getProperty("stoppingdown", "http://stoppingdown.net");
protected static final String URL_GALLERY_TEMPLATE = "%s%s/images.xml";
protected static final DocumentBuilderFactory PARSER_FACTORY = DocumentBuilderFactory.newInstance();
// FIXME: XPath stuff is not thread-safe - fix!
protected static final XPathFactory XPATH_FACTORY = XPathFactory.newInstance();
private static final XPathExpression XPATH_STILLIMAGE_EXPR;
@Nonnull
protected final String baseUrl;
/**
* A local cache for finders. It's advisable, since clients will frequently retrieve a finder because of pagination.
*/
private final Map<String, Collection<PathAwareEntity>> photoCollectionCache = new ConcurrentHashMap<>();
/*******************************************************************************************************************
*
******************************************************************************************************************/
static
{
try
{
final XPath xpath = XPATH_FACTORY.newXPath();
XPATH_STILLIMAGE_EXPR = xpath.compile("/gallery/stillImage");
}
catch (XPathExpressionException e)
{
throw new ExceptionInInitializerError(e);
}
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
@Override @Nonnull
public PathAwareFinder findPhotos (@Nonnull final MediaFolder parent)
{
throw new UnsupportedOperationException("must be implemented in subclasses");
}
/*******************************************************************************************************************
*
*
*
******************************************************************************************************************/
@Scheduled(fixedDelay = 14_400_000) // 12 hours TODO: yes, can use properties here
private void clearCaches()
{
log.info("clearCaches()");
clearCachesImpl();
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
protected void clearCachesImpl()
{
photoCollectionCache.clear();
}
/*******************************************************************************************************************
*
* Creates a collection of entities for the given gallery URL.
*
* @param parent the parent node
* @param galleryUrl the gallery URL
* @return the collection of entities
*
******************************************************************************************************************/
@Nonnull
@VisibleForTesting Collection<PathAwareEntity> findPhotos (@Nonnull final MediaFolder parent,
@Nonnull final String galleryUrl)
{
log.debug("findPhotos({}, {}", parent, galleryUrl);
return photoCollectionCache.computeIfAbsent(galleryUrl, u ->
{
try
{
final Document document = downloadXml(galleryUrl);
final NodeList nodes = (NodeList)XPATH_STILLIMAGE_EXPR.evaluate(document, XPathConstants.NODESET);
final Collection<PathAwareEntity> photoItems = new ArrayList<>();
for (int i = 0; i < nodes.getLength(); i++)
{
final Node node = nodes.item(i);
final String id = getAttribute(node, "id");
final String title = getAttribute(node, "title");
photoItems.add(new PhotoItem(parent, id, title));
}
return photoItems;
}
catch (SAXException | IOException | XPathExpressionException | ParserConfigurationException e)
{
throw new RuntimeException(e);
}
});
}
/*******************************************************************************************************************
*
******************************************************************************************************************/
// FIXME: implement a local cache on disk
@Nonnull
protected Document downloadXml (@Nonnull String url)
throws SAXException, ParserConfigurationException, IOException
{
log.info("downloadXml({})", url);
url = url.replaceAll("(^.*)\\/([0-9]{2})-([0-9]{2})\\/(.*)$", "$1/$2/$3/$4");
if (url.startsWith("file:") && url.endsWith("/")) // To support local test resources
{
url += "/index.xhtml";
}
return PARSER_FACTORY.newDocumentBuilder().parse(url);
}
/*******************************************************************************************************************
*
******************************************************************************************************************/
@Nonnull
protected static String getAttribute (@Nonnull final Node node, @Nonnull final String attrName)
throws DOMException
{
return node.getAttributes().getNamedItem(attrName).getNodeValue();
}
}