opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/DelayedDataTreeListenerRegistration.java

   1 /*
   2  * Copyright (c) 2015 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.controller.cluster.datastore;
   9
  10 import com.google.common.base.Preconditions;
  11 import javax.annotation.concurrent.GuardedBy;
  12 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  13 import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeChangeListener;
  14 import org.opendaylight.yangtools.concepts.ListenerRegistration;
  15
  16 /**
  17  * Intermediate proxy registration returned to the user when we cannot
  18  * instantiate the registration immediately. It provides a bridge to
  19  * a real registration which may materialize at some point in the future.
  20  */
  21 final class DelayedDataTreeListenerRegistration implements ListenerRegistration<DOMDataTreeChangeListener> {
  22     private final RegisterDataTreeChangeListener registerTreeChangeListener;
  23     private volatile ListenerRegistration<DOMDataTreeChangeListener> delegate;
  24     @GuardedBy("this")
  25     private boolean closed;
  26
  27     DelayedDataTreeListenerRegistration(final RegisterDataTreeChangeListener registerTreeChangeListener) {
  28         this.registerTreeChangeListener = Preconditions.checkNotNull(registerTreeChangeListener);
  29     }
  30
  31     synchronized void createDelegate(final DelegateFactory<RegisterDataTreeChangeListener, ListenerRegistration<DOMDataTreeChangeListener>> factory) {
  32         if (!closed) {
  33             this.delegate = factory.createDelegate(registerTreeChangeListener);
  34         }
  35     }
  36
  37     @Override
  38     public DOMDataTreeChangeListener getInstance() {
  39         final ListenerRegistration<DOMDataTreeChangeListener> d = delegate;
  40         return d == null ? null : d.getInstance();
  41     }
  42
  43     @Override
  44     public synchronized void close() {
  45         if (!closed) {
  46             closed = true;
  47             if (delegate != null) {
  48                 delegate.close();
  49             }
  50         }
  51     }
  52 }
  53