2 * Copyright (c) 2016 Cisco Systems, Inc. and others. All rights reserved.
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
8 package org.opendaylight.controller.cluster.datastore.persisted;
10 import static com.google.common.base.Verify.verifyNotNull;
12 import java.io.Externalizable;
13 import java.io.Serializable;
14 import org.eclipse.jdt.annotation.NonNull;
17 * Base class for various bits of metadata attached to a {@link MetadataShardDataTreeSnapshot}. This class is not
18 * an interface because we want to make sure all subclasses implement the externalizable proxy pattern, for which
19 * we need to force {@link #writeReplace()} to be abstract. We do that by making it final and exposing a protected
20 * {@link #externalizableProxy()} method.
23 * All concrete subclasses of this class should be final so as to form a distinct set of possible metadata. Since
24 * metadata is serialized along with {@link MetadataShardDataTreeSnapshot}, this set is part of the serialization format
25 * guarded by {@link PayloadVersion}.
28 * If a new metadata type is introduced or a type is removed, {@link PayloadVersion} needs to be bumped to ensure
31 * @author Robert Varga
33 public abstract class ShardDataTreeSnapshotMetadata<T extends ShardDataTreeSnapshotMetadata<T>>
34 implements Serializable {
35 private static final long serialVersionUID = 1L;
37 ShardDataTreeSnapshotMetadata() {
38 // Prevent subclassing from outside of this package
41 final Object writeReplace() {
42 return verifyNotNull(externalizableProxy(), "Null externalizable proxy from %s", getClass());
46 * Return an Externalizable proxy.
48 * @return Externalizable proxy, may not be null
50 protected abstract @NonNull Externalizable externalizableProxy();
52 public abstract Class<T> getType();