restconf/sal-rest-connector/src/main/java/org/opendaylight/netconf/sal/streams/listeners/ListenerAdapter.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.netconf.sal.streams.listeners;
   9
  10 import com.google.common.base.Preconditions;
  11 import com.google.common.eventbus.AsyncEventBus;
  12 import com.google.common.eventbus.EventBus;
  13 import com.google.common.eventbus.Subscribe;
  14 import io.netty.channel.Channel;
  15 import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
  16 import io.netty.util.internal.ConcurrentSet;
  17 import java.io.ByteArrayOutputStream;
  18 import java.io.IOException;
  19 import java.io.OutputStreamWriter;
  20 import java.io.UnsupportedEncodingException;
  21 import java.nio.charset.StandardCharsets;
  22 import java.text.SimpleDateFormat;
  23 import java.util.Collection;
  24 import java.util.Date;
  25 import java.util.HashMap;
  26 import java.util.Map;
  27 import java.util.Map.Entry;
  28 import java.util.Random;
  29 import java.util.Set;
  30 import java.util.concurrent.Executors;
  31 import java.util.regex.Pattern;
  32 import javax.xml.parsers.DocumentBuilder;
  33 import javax.xml.parsers.DocumentBuilderFactory;
  34 import javax.xml.parsers.ParserConfigurationException;
  35 import javax.xml.stream.XMLOutputFactory;
  36 import javax.xml.stream.XMLStreamException;
  37 import javax.xml.stream.XMLStreamWriter;
  38 import javax.xml.transform.OutputKeys;
  39 import javax.xml.transform.Transformer;
  40 import javax.xml.transform.TransformerException;
  41 import javax.xml.transform.TransformerFactory;
  42 import javax.xml.transform.dom.DOMResult;
  43 import javax.xml.transform.dom.DOMSource;
  44 import javax.xml.transform.stream.StreamResult;
  45 import org.json.JSONObject;
  46 import org.json.XML;
  47 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeEvent;
  48 import org.opendaylight.controller.md.sal.dom.api.DOMDataChangeListener;
  49 import org.opendaylight.netconf.sal.restconf.impl.ControllerContext;
  50 import org.opendaylight.yang.gen.v1.urn.sal.restconf.event.subscription.rev140708.NotificationOutputTypeGrouping.NotificationOutputType;
  51 import org.opendaylight.yangtools.concepts.ListenerRegistration;
  52 import org.opendaylight.yangtools.yang.common.QName;
  53 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  54 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifierWithPredicates;
  55 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeWithValue;
  56 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
  57 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  58 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  59 import org.opendaylight.yangtools.yang.data.api.schema.UnkeyedListEntryNode;
  60 import org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeStreamWriter;
  61 import org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeWriter;
  62 import org.opendaylight.yangtools.yang.data.impl.codec.xml.XMLStreamNormalizedNodeStreamWriter;
  63 import org.opendaylight.yangtools.yang.data.impl.codec.xml.XmlDocumentUtils;
  64 import org.opendaylight.yangtools.yang.data.util.DataSchemaContextTree;
  65 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  66 import org.opendaylight.yangtools.yang.model.api.SchemaPath;
  67 import org.slf4j.Logger;
  68 import org.slf4j.LoggerFactory;
  69 import org.w3c.dom.Document;
  70 import org.w3c.dom.Element;
  71 import org.w3c.dom.Node;
  72
  73 /**
  74  * {@link ListenerAdapter} is responsible to track events, which occurred by changing data in data source.
  75  */
  76 public class ListenerAdapter implements DOMDataChangeListener {
  77
  78     private static final Logger LOG = LoggerFactory.getLogger(ListenerAdapter.class);
  79     private static final DocumentBuilderFactory DBF = DocumentBuilderFactory.newInstance();
  80     private static final TransformerFactory FACTORY = TransformerFactory.newInstance();
  81     private static final Pattern RFC3339_PATTERN = Pattern.compile("(\\d\\d)(\\d\\d)$");
  82
  83     private static final SimpleDateFormat RFC3339 = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ssZ");
  84
  85     private final YangInstanceIdentifier path;
  86     private ListenerRegistration<DOMDataChangeListener> registration;
  87     private final String streamName;
  88     private Set<Channel> subscribers = new ConcurrentSet<>();
  89     private final EventBus eventBus;
  90     private final EventBusChangeRecorder eventBusChangeRecorder;
  91     private final NotificationOutputType outputType;
  92
  93     /**
  94      * Creates new {@link ListenerAdapter} listener specified by path and stream
  95      * name.
  96      *
  97      * @param path
  98      *            Path to data in data store.
  99      * @param streamName
 100      *            The name of the stream.
 101      * @param outputType
 102      *            - type of output on notification (JSON, XML)
 103      */
 104     ListenerAdapter(final YangInstanceIdentifier path, final String streamName,
 105             final NotificationOutputType outputType) {
 106         this.outputType = outputType;
 107         Preconditions.checkNotNull(path);
 108         Preconditions.checkArgument((streamName != null) && !streamName.isEmpty());
 109         this.path = path;
 110         this.streamName = streamName;
 111         this.eventBus = new AsyncEventBus(Executors.newSingleThreadExecutor());
 112         this.eventBusChangeRecorder = new EventBusChangeRecorder();
 113         this.eventBus.register(this.eventBusChangeRecorder);
 114     }
 115
 116     @Override
 117     public void onDataChanged(final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change) {
 118         if (!change.getCreatedData().isEmpty() || !change.getUpdatedData().isEmpty()
 119                 || !change.getRemovedPaths().isEmpty()) {
 120             final String xml = prepareXmlFrom(change);
 121             final Event event = new Event(EventType.NOTIFY);
 122             if (this.outputType.equals(NotificationOutputType.JSON)) {
 123                 final JSONObject jsonObject = XML.toJSONObject(xml);
 124                 event.setData(jsonObject.toString());
 125             } else {
 126                 event.setData(xml);
 127             }
 128             this.eventBus.post(event);
 129         }
 130     }
 131
 132     /**
 133      * Tracks events of data change by customer.
 134      */
 135     private final class EventBusChangeRecorder {
 136         @Subscribe
 137         public void recordCustomerChange(final Event event) {
 138             if (event.getType() == EventType.REGISTER) {
 139                 final Channel subscriber = event.getSubscriber();
 140                 if (!ListenerAdapter.this.subscribers.contains(subscriber)) {
 141                     ListenerAdapter.this.subscribers.add(subscriber);
 142                 }
 143             } else if (event.getType() == EventType.DEREGISTER) {
 144                 ListenerAdapter.this.subscribers.remove(event.getSubscriber());
 145                 Notificator.removeListenerIfNoSubscriberExists(ListenerAdapter.this);
 146             } else if (event.getType() == EventType.NOTIFY) {
 147                 for (final Channel subscriber : ListenerAdapter.this.subscribers) {
 148                     if (subscriber.isActive()) {
 149                         LOG.debug("Data are sent to subscriber {}:", subscriber.remoteAddress());
 150                         subscriber.writeAndFlush(new TextWebSocketFrame(event.getData()));
 151                     } else {
 152                         LOG.debug("Subscriber {} is removed - channel is not active yet.", subscriber.remoteAddress());
 153                         ListenerAdapter.this.subscribers.remove(subscriber);
 154                     }
 155                 }
 156             }
 157         }
 158     }
 159
 160     /**
 161      * Represents event of specific {@link EventType} type, holds data and {@link Channel} subscriber.
 162      */
 163     private final class Event {
 164         private final EventType type;
 165         private Channel subscriber;
 166         private String data;
 167
 168         /**
 169          * Creates new event specified by {@link EventType} type.
 170          *
 171          * @param type
 172          *            EventType
 173          */
 174         public Event(final EventType type) {
 175             this.type = type;
 176         }
 177
 178         /**
 179          * Gets the {@link Channel} subscriber.
 180          *
 181          * @return Channel
 182          */
 183         public Channel getSubscriber() {
 184             return this.subscriber;
 185         }
 186
 187         /**
 188          * Sets subscriber for event.
 189          *
 190          * @param subscriber
 191          *            Channel
 192          */
 193         public void setSubscriber(final Channel subscriber) {
 194             this.subscriber = subscriber;
 195         }
 196
 197         /**
 198          * Gets event String.
 199          *
 200          * @return String representation of event data.
 201          */
 202         public String getData() {
 203             return this.data;
 204         }
 205
 206         /**
 207          * Sets event data.
 208          *
 209          * @param data String.
 210          */
 211         public void setData(final String data) {
 212             this.data = data;
 213         }
 214
 215         /**
 216          * Gets event type.
 217          *
 218          * @return The type of the event.
 219          */
 220         public EventType getType() {
 221             return this.type;
 222         }
 223     }
 224
 225     /**
 226      * Type of the event.
 227      */
 228     private enum EventType {
 229         REGISTER,
 230         DEREGISTER,
 231         NOTIFY;
 232     }
 233
 234     /**
 235      * Prepare data in printable form and transform it to String.
 236      *
 237      * @param change
 238      *            DataChangeEvent
 239      * @return Data in printable form.
 240      */
 241     private String prepareXmlFrom(final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change) {
 242         final SchemaContext schemaContext = ControllerContext.getInstance().getGlobalSchema();
 243         final DataSchemaContextTree dataContextTree =  DataSchemaContextTree.from(schemaContext);
 244         final Document doc = createDocument();
 245         final Element notificationElement = doc.createElementNS("urn:ietf:params:xml:ns:netconf:notification:1.0",
 246                 "notification");
 247
 248         doc.appendChild(notificationElement);
 249
 250         final Element eventTimeElement = doc.createElement("eventTime");
 251         eventTimeElement.setTextContent(toRFC3339(new Date()));
 252         notificationElement.appendChild(eventTimeElement);
 253
 254         final Element dataChangedNotificationEventElement = doc.createElementNS(
 255                 "urn:opendaylight:params:xml:ns:yang:controller:md:sal:remote", "data-changed-notification");
 256
 257         addValuesToDataChangedNotificationEventElement(doc, dataChangedNotificationEventElement, change,
 258                 schemaContext, dataContextTree);
 259         notificationElement.appendChild(dataChangedNotificationEventElement);
 260
 261         try {
 262             final ByteArrayOutputStream out = new ByteArrayOutputStream();
 263             final Transformer transformer = FACTORY.newTransformer();
 264             transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
 265             transformer.setOutputProperty(OutputKeys.METHOD, "xml");
 266             transformer.setOutputProperty(OutputKeys.INDENT, "yes");
 267             transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
 268             transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
 269             transformer.transform(new DOMSource(doc),
 270                     new StreamResult(new OutputStreamWriter(out, StandardCharsets.UTF_8)));
 271             final byte[] charData = out.toByteArray();
 272             return new String(charData, "UTF-8");
 273         } catch (TransformerException | UnsupportedEncodingException e) {
 274             final String msg = "Error during transformation of Document into String";
 275             LOG.error(msg, e);
 276             return msg;
 277         }
 278     }
 279
 280     /**
 281      * Formats data specified by RFC3339.
 282      *
 283      * @param d
 284      *            Date
 285      * @return Data specified by RFC3339.
 286      */
 287     public static String toRFC3339(final Date d) {
 288         return RFC3339_PATTERN.matcher(RFC3339.format(d)).replaceAll("$1:$2");
 289     }
 290
 291     /**
 292      * Creates {@link Document} document.
 293      * @return {@link Document} document.
 294      */
 295     public static Document createDocument() {
 296         final DocumentBuilder bob;
 297         try {
 298             bob = DBF.newDocumentBuilder();
 299         } catch (final ParserConfigurationException e) {
 300             return null;
 301         }
 302         return bob.newDocument();
 303     }
 304
 305     /**
 306      * Adds values to data changed notification event element.
 307      *
 308      * @param doc
 309      *            {@link Document}
 310      * @param dataChangedNotificationEventElement
 311      *            {@link Element}
 312      * @param change
 313      *            {@link AsyncDataChangeEvent}
 314      */
 315     private void addValuesToDataChangedNotificationEventElement(final Document doc,
 316             final Element dataChangedNotificationEventElement,
 317             final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change,
 318             final SchemaContext  schemaContext, final DataSchemaContextTree dataSchemaContextTree) {
 319
 320         addCreatedChangedValuesFromDataToElement(doc, change.getCreatedData().entrySet(),
 321                 dataChangedNotificationEventElement,
 322                 Operation.CREATED, schemaContext, dataSchemaContextTree);
 323
 324         addCreatedChangedValuesFromDataToElement(doc, change.getUpdatedData().entrySet(),
 325                     dataChangedNotificationEventElement,
 326                     Operation.UPDATED, schemaContext, dataSchemaContextTree);
 327
 328         addValuesFromDataToElement(doc, change.getRemovedPaths(), dataChangedNotificationEventElement,
 329                 Operation.DELETED);
 330     }
 331
 332     /**
 333      * Adds values from data to element.
 334      *
 335      * @param doc
 336      *            {@link Document}
 337      * @param data
 338      *            Set of {@link YangInstanceIdentifier}.
 339      * @param element
 340      *            {@link Element}
 341      * @param operation
 342      *            {@link Operation}
 343      */
 344     private void addValuesFromDataToElement(final Document doc, final Set<YangInstanceIdentifier> data,
 345             final Element element, final Operation operation) {
 346         if ((data == null) || data.isEmpty()) {
 347             return;
 348         }
 349         for (final YangInstanceIdentifier path : data) {
 350             if (!ControllerContext.getInstance().isNodeMixin(path)) {
 351                 final Node node = createDataChangeEventElement(doc, path, operation);
 352                 element.appendChild(node);
 353             }
 354         }
 355     }
 356
 357     private void addCreatedChangedValuesFromDataToElement(final Document doc, final Set<Entry<YangInstanceIdentifier,
 358                 NormalizedNode<?,?>>> data, final Element element, final Operation operation, final SchemaContext
 359             schemaContext, final DataSchemaContextTree dataSchemaContextTree) {
 360         if ((data == null) || data.isEmpty()) {
 361             return;
 362         }
 363         for (final Entry<YangInstanceIdentifier, NormalizedNode<?, ?>> entry : data) {
 364             if (!ControllerContext.getInstance().isNodeMixin(entry.getKey())) {
 365                 final Node node = createCreatedChangedDataChangeEventElement(doc, entry, operation, schemaContext,
 366                         dataSchemaContextTree);
 367                 element.appendChild(node);
 368             }
 369         }
 370     }
 371
 372     /**
 373      * Creates changed event element from data.
 374      *
 375      * @param doc
 376      *            {@link Document}
 377      * @param path
 378      *            Path to data in data store.
 379      * @param operation
 380      *            {@link Operation}
 381      * @return {@link Node} node represented by changed event element.
 382      */
 383     private Node createDataChangeEventElement(final Document doc, final YangInstanceIdentifier path,
 384             final Operation operation) {
 385         final Element dataChangeEventElement = doc.createElement("data-change-event");
 386         final Element pathElement = doc.createElement("path");
 387         addPathAsValueToElement(path, pathElement);
 388         dataChangeEventElement.appendChild(pathElement);
 389
 390         final Element operationElement = doc.createElement("operation");
 391         operationElement.setTextContent(operation.value);
 392         dataChangeEventElement.appendChild(operationElement);
 393
 394         return dataChangeEventElement;
 395     }
 396
 397     private Node createCreatedChangedDataChangeEventElement(final Document doc, final Entry<YangInstanceIdentifier,
 398             NormalizedNode<?, ?>> entry, final Operation operation, final SchemaContext
 399             schemaContext, final DataSchemaContextTree dataSchemaContextTree) {
 400         final Element dataChangeEventElement = doc.createElement("data-change-event");
 401         final Element pathElement = doc.createElement("path");
 402         final YangInstanceIdentifier path = entry.getKey();
 403         addPathAsValueToElement(path, pathElement);
 404         dataChangeEventElement.appendChild(pathElement);
 405
 406         final Element operationElement = doc.createElement("operation");
 407         operationElement.setTextContent(operation.value);
 408         dataChangeEventElement.appendChild(operationElement);
 409
 410         try {
 411             final DOMResult domResult = writeNormalizedNode(entry.getValue(), path,
 412                     schemaContext, dataSchemaContextTree);
 413             final Node result = doc.importNode(domResult.getNode().getFirstChild(), true);
 414             final Element dataElement = doc.createElement("data");
 415             dataElement.appendChild(result);
 416             dataChangeEventElement.appendChild(dataElement);
 417         } catch (final IOException e) {
 418             LOG.error("Error in writer ", e);
 419         } catch (final XMLStreamException e) {
 420             LOG.error("Error processing stream", e);
 421         }
 422
 423         return dataChangeEventElement;
 424     }
 425
 426     private static DOMResult writeNormalizedNode(final NormalizedNode<?, ?> normalized,
 427                                                  final YangInstanceIdentifier path, final SchemaContext context,
 428                                                  final DataSchemaContextTree dataSchemaContextTree)
 429             throws IOException, XMLStreamException {
 430         final XMLOutputFactory XML_FACTORY = XMLOutputFactory.newFactory();
 431         final Document doc = XmlDocumentUtils.getDocument();
 432         final DOMResult result = new DOMResult(doc);
 433         NormalizedNodeWriter normalizedNodeWriter = null;
 434         NormalizedNodeStreamWriter normalizedNodeStreamWriter = null;
 435         XMLStreamWriter writer = null;
 436         final SchemaPath nodePath;
 437
 438         if ((normalized instanceof MapEntryNode) || (normalized instanceof UnkeyedListEntryNode)) {
 439             nodePath = dataSchemaContextTree.getChild(path).getDataSchemaNode().getPath();
 440         } else {
 441             nodePath = dataSchemaContextTree.getChild(path).getDataSchemaNode().getPath().getParent();
 442         }
 443
 444         try {
 445             writer = XML_FACTORY.createXMLStreamWriter(result);
 446             normalizedNodeStreamWriter = XMLStreamNormalizedNodeStreamWriter.create(writer, context, nodePath);
 447             normalizedNodeWriter = NormalizedNodeWriter.forStreamWriter(normalizedNodeStreamWriter);
 448
 449             normalizedNodeWriter.write(normalized);
 450
 451             normalizedNodeWriter.flush();
 452         } finally {
 453             if (normalizedNodeWriter != null) {
 454                 normalizedNodeWriter.close();
 455             }
 456             if (normalizedNodeStreamWriter != null) {
 457                 normalizedNodeStreamWriter.close();
 458             }
 459             if (writer != null) {
 460                 writer.close();
 461             }
 462         }
 463
 464         return result;
 465     }
 466
 467     /**
 468      * Adds path as value to element.
 469      *
 470      * @param path
 471      *            Path to data in data store.
 472      * @param element
 473      *            {@link Element}
 474      */
 475     private void addPathAsValueToElement(final YangInstanceIdentifier path, final Element element) {
 476         // Map< key = namespace, value = prefix>
 477         final Map<String, String> prefixes = new HashMap<>();
 478         final YangInstanceIdentifier normalizedPath = ControllerContext.getInstance().toXpathRepresentation(path);
 479         final StringBuilder textContent = new StringBuilder();
 480
 481         // FIXME: BUG-1281: this is duplicated code from yangtools (BUG-1275)
 482         for (final PathArgument pathArgument : normalizedPath.getPathArguments()) {
 483             if (pathArgument instanceof YangInstanceIdentifier.AugmentationIdentifier) {
 484                 continue;
 485             }
 486             textContent.append("/");
 487             writeIdentifierWithNamespacePrefix(element, textContent, pathArgument.getNodeType(), prefixes);
 488             if (pathArgument instanceof NodeIdentifierWithPredicates) {
 489                 final Map<QName, Object> predicates = ((NodeIdentifierWithPredicates) pathArgument).getKeyValues();
 490                 for (final QName keyValue : predicates.keySet()) {
 491                     final String predicateValue = String.valueOf(predicates.get(keyValue));
 492                     textContent.append("[");
 493                     writeIdentifierWithNamespacePrefix(element, textContent, keyValue, prefixes);
 494                     textContent.append("='");
 495                     textContent.append(predicateValue);
 496                     textContent.append("'");
 497                     textContent.append("]");
 498                 }
 499             } else if (pathArgument instanceof NodeWithValue) {
 500                 textContent.append("[.='");
 501                 textContent.append(((NodeWithValue) pathArgument).getValue());
 502                 textContent.append("'");
 503                 textContent.append("]");
 504             }
 505         }
 506         element.setTextContent(textContent.toString());
 507     }
 508
 509     /**
 510      * Writes identifier that consists of prefix and QName.
 511      *
 512      * @param element
 513      *            {@link Element}
 514      * @param textContent
 515      *            StringBuilder
 516      * @param qName
 517      *            QName
 518      * @param prefixes
 519      *            Map of namespaces and prefixes.
 520      */
 521     private static void writeIdentifierWithNamespacePrefix(final Element element, final StringBuilder textContent,
 522             final QName qName, final Map<String, String> prefixes) {
 523         final String namespace = qName.getNamespace().toString();
 524         String prefix = prefixes.get(namespace);
 525         if (prefix == null) {
 526             prefix = generateNewPrefix(prefixes.values());
 527         }
 528
 529         element.setAttribute("xmlns:" + prefix, namespace);
 530         textContent.append(prefix);
 531         prefixes.put(namespace, prefix);
 532
 533         textContent.append(":");
 534         textContent.append(qName.getLocalName());
 535     }
 536
 537     /**
 538      * Generates new prefix which consists of four random characters <a-z>.
 539      *
 540      * @param prefixes
 541      *            Collection of prefixes.
 542      * @return New prefix which consists of four random characters <a-z>.
 543      */
 544     private static String generateNewPrefix(final Collection<String> prefixes) {
 545         StringBuilder result = null;
 546         final Random random = new Random();
 547         do {
 548             result = new StringBuilder();
 549             for (int i = 0; i < 4; i++) {
 550                 final int randomNumber = 0x61 + (Math.abs(random.nextInt()) % 26);
 551                 result.append(Character.toChars(randomNumber));
 552             }
 553         } while (prefixes.contains(result.toString()));
 554
 555         return result.toString();
 556     }
 557
 558     /**
 559      * Gets path pointed to data in data store.
 560      *
 561      * @return Path pointed to data in data store.
 562      */
 563     public YangInstanceIdentifier getPath() {
 564         return this.path;
 565     }
 566
 567     /**
 568      * Sets {@link ListenerRegistration} registration.
 569      *
 570      * @param registration DOMDataChangeListener registration
 571      */
 572     public void setRegistration(final ListenerRegistration<DOMDataChangeListener> registration) {
 573         this.registration = registration;
 574     }
 575
 576     /**
 577      * Gets the name of the stream.
 578      *
 579      * @return The name of the stream.
 580      */
 581     public String getStreamName() {
 582         return this.streamName;
 583     }
 584
 585     /**
 586      * Removes all subscribers and unregisters event bus change recorder form event bus.
 587      */
 588     public void close() throws Exception {
 589         this.subscribers = new ConcurrentSet<>();
 590         this.registration.close();
 591         this.registration = null;
 592         this.eventBus.unregister(this.eventBusChangeRecorder);
 593     }
 594
 595     /**
 596      * Checks if {@link ListenerRegistration} registration exist.
 597      *
 598      * @return True if exist, false otherwise.
 599      */
 600     public boolean isListening() {
 601         return this.registration == null ? false : true;
 602     }
 603
 604     /**
 605      * Creates event of type {@link EventType#REGISTER}, set {@link Channel} subscriber to the event and post event into
 606      * event bus.
 607      *
 608      * @param subscriber
 609      *            Channel
 610      */
 611     public void addSubscriber(final Channel subscriber) {
 612         if (!subscriber.isActive()) {
 613             LOG.debug("Channel is not active between websocket server and subscriber {}" + subscriber.remoteAddress());
 614         }
 615         final Event event = new Event(EventType.REGISTER);
 616         event.setSubscriber(subscriber);
 617         this.eventBus.post(event);
 618     }
 619
 620     /**
 621      * Creates event of type {@link EventType#DEREGISTER}, sets {@link Channel} subscriber to the event and posts event
 622      * into event bus.
 623      *
 624      * @param subscriber
 625      */
 626     public void removeSubscriber(final Channel subscriber) {
 627         LOG.debug("Subscriber {} is removed.", subscriber.remoteAddress());
 628         final Event event = new Event(EventType.DEREGISTER);
 629         event.setSubscriber(subscriber);
 630         this.eventBus.post(event);
 631     }
 632
 633     /**
 634      * Checks if exists at least one {@link Channel} subscriber.
 635      *
 636      * @return True if exist at least one {@link Channel} subscriber, false otherwise.
 637      */
 638     public boolean hasSubscribers() {
 639         return !this.subscribers.isEmpty();
 640     }
 641
 642     /**
 643      * Consists of two types {@link Store#CONFIG} and {@link Store#OPERATION}.
 644      */
 645     private static enum Store {
 646         CONFIG("config"),
 647         OPERATION("operation");
 648
 649         private final String value;
 650
 651         private Store(final String value) {
 652             this.value = value;
 653         }
 654     }
 655
 656     /**
 657      * Consists of three types {@link Operation#CREATED}, {@link Operation#UPDATED} and {@link Operation#DELETED}.
 658      */
 659     private static enum Operation {
 660         CREATED("created"),
 661         UPDATED("updated"),
 662         DELETED("deleted");
 663
 664         private final String value;
 665
 666         private Operation(final String value) {
 667             this.value = value;
 668         }
 669     }
 670
 671 }