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package eu.dnetlib.enabling.is.sn;
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import java.io.StringWriter;
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import java.util.Collection;
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import javax.xml.transform.Transformer;
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import javax.xml.transform.TransformerException;
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import javax.xml.transform.TransformerFactory;
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import javax.xml.transform.dom.DOMSource;
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import javax.xml.transform.stream.StreamResult;
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import javax.xml.xpath.XPath;
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import javax.xml.xpath.XPathConstants;
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import javax.xml.xpath.XPathExpressionException;
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import javax.xml.xpath.XPathFactory;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.w3c.dom.Node;
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import eu.dnetlib.enabling.is.sn.resourcestate.ResourceStateNotificationDetector;
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import eu.dnetlib.enabling.is.sn.resourcestate.ResourceStateSubscription;
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import eu.dnetlib.enabling.is.sn.resourcestate.ResourceStateSubscriptionRegistry;
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import eu.dnetlib.enabling.tools.OpaqueResource;
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/**
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* This notification detector uses a local xmldb trigger as a source of events.
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*
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* @author marko
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*
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*/
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public class NotificationDetectorImpl extends AbstractNotificationDetector implements ResourceStateNotificationDetector<OpaqueResource> {
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/**
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* logger.
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*/
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private static final Log log = LogFactory.getLog(NotificationDetectorImpl.class); // NOPMD by marko on 11/24/08 5:02 PM
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/**
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* subscription registries to lookup.
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*/
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private Collection<ResourceStateSubscriptionRegistry> registries;
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/**
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* {@inheritDoc}
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*
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* @see eu.dnetlib.enabling.is.sn.resourcestate.ResourceStateNotificationDetector#resourceCreated(java.lang.Object)
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*/
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@Override
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public void resourceCreated(final OpaqueResource newResource) {
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log.debug("resource created: " + registries);
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for (ResourceStateSubscriptionRegistry registry : registries) {
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for (ResourceStateSubscription sub : registry.listMatchingSubscriptions(ResourceStateSubscription.PREFIX_CREATE, newResource
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.getResourceType(), newResource.getResourceId()))
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if (matchPath(newResource, sub.getXpath()))
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send(sub, newResource, ResourceStateSubscription.PREFIX_CREATE);
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}
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}
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/**
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* helper method. sends a notification for a given prefix.
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*
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* @param sub
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* subscription
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* @param resource
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* resource
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* @param prefix
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* prefix
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*/
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private void send(final ResourceStateSubscription sub, final OpaqueResource resource, final String prefix) {
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log.debug("RESOURCE " + resource);
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log.debug("id: " + resource.getResourceId());
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log.debug("dom: " + resource.asDom());
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final StringBuffer topicBuffer = new StringBuffer();
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if (sub.getPrefix() == null && "*".equals(sub.getPrefix()))
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topicBuffer.append(prefix);
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else
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topicBuffer.append(sub.getPrefix());
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topicBuffer.append('.');
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topicBuffer.append(sub.getType());
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topicBuffer.append('.');
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topicBuffer.append(sub.getResourceId());
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if (sub.getXpath() != null && !sub.getXpath().isEmpty()) {
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topicBuffer.append(sub.getXpath().replace('/', '.'));
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}
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getSender().send(sub.getSubscriberAsEpr(), new NotificationMessage(sub.getSubscriptionId(), topicBuffer.toString(), resource.getResourceId(), // NOPMD
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resource.asString()));
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}
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/**
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* {@inheritDoc}
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*
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* @see eu.dnetlib.enabling.is.sn.resourcestate.ResourceStateNotificationDetector#resourceDeleted(java.lang.Object)
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*/
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@Override
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public void resourceDeleted(final OpaqueResource oldResource) {
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log.debug("resource deleted: " + registries);
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for (ResourceStateSubscriptionRegistry registry : registries) {
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for (ResourceStateSubscription sub : registry.listMatchingSubscriptions(ResourceStateSubscription.PREFIX_DELETE, oldResource
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.getResourceType(), oldResource.getResourceId()))
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if (matchPath(oldResource, sub.getXpath()))
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send(sub, oldResource, ResourceStateSubscription.PREFIX_DELETE);
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}
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}
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/**
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* {@inheritDoc}
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*
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* @see eu.dnetlib.enabling.is.sn.resourcestate.ResourceStateNotificationDetector#resourceUpdated(java.lang.Object,
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* java.lang.Object)
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*/
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@Override
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public void resourceUpdated(final OpaqueResource oldResource, final OpaqueResource newResource) {
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log.debug("resource updated: " + registries);
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for (ResourceStateSubscriptionRegistry registry : registries) {
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for (ResourceStateSubscription sub : registry.listMatchingSubscriptions(ResourceStateSubscription.PREFIX_UPDATE, oldResource
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.getResourceType(), oldResource.getResourceId()))
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if (comparePath(oldResource, newResource, sub.getXpath())) {
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log.debug("updated, sending: " + newResource.asString());
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send(sub, newResource, ResourceStateSubscription.PREFIX_UPDATE);
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}
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}
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}
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/**
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* check if an xpath matches a given resource.
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*
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* @param resource
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* resource
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* @param xpath
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* xpath
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* @return true if the resource has some value for the given path
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*/
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private boolean matchPath(final OpaqueResource resource, final String xpath) {
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// by convention empty xpath matches any document
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if (xpath == null || xpath.isEmpty())
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return true;
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final XPath xpa = XPathFactory.newInstance().newXPath();
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try {
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return !xpa.evaluate(xpath, resource.asDom()).isEmpty();
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} catch (XPathExpressionException e) {
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log.warn("wrong xpath expression, notification possibly missed", e);
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}
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return false;
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}
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/**
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* compare the content of two profiles for the same xpath. Return true if some change has been made so that the
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* notification can be delivered.
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*
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* @param oldResource
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* old version
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* @param newResource
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* new version
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* @param xpath
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* XPath
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* @return true if the two documents differ under a given path
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*/
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private boolean comparePath(final OpaqueResource oldResource, final OpaqueResource newResource, final String xpath) {
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// by convention empty xpath matches any document
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if (oldResource == null || newResource == null || xpath == null || xpath.isEmpty())
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return true;
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final XPath xpa = XPathFactory.newInstance().newXPath();
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try {
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final Transformer transformer = TransformerFactory.newInstance().newTransformer();
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final Node left = (Node) xpa.evaluate(xpath, oldResource.asDom(), XPathConstants.NODE);
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final Node right = (Node) xpa.evaluate(xpath, newResource.asDom(), XPathConstants.NODE);
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if (left==null || right==null) {
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if (left != null) {
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return true;
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}
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else {
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if (right != null) {
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return true;
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}
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else {
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return false;
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}
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}
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}
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final StringWriter leftWriter = new StringWriter();
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final StringWriter rightWriter = new StringWriter();
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transformer.transform(new DOMSource(left), new StreamResult(leftWriter));
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transformer.transform(new DOMSource(right), new StreamResult(rightWriter));
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return !leftWriter.toString().equals(rightWriter.toString());
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} catch (XPathExpressionException e) {
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log.warn("wrong xpath expression, notification possibly missed", e);
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} catch (TransformerException e) {
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log.warn("serialization problem", e);
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}
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return false;
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}
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public Collection<ResourceStateSubscriptionRegistry> getRegistries() {
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return registries;
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}
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public void setRegistries(final Collection<ResourceStateSubscriptionRegistry> registries) {
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this.registries = registries;
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}
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}
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