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.access.concepts;
10 import com.google.common.annotations.Beta;
11 import com.google.common.annotations.VisibleForTesting;
12 import com.google.common.base.MoreObjects;
13 import com.google.common.base.MoreObjects.ToStringHelper;
14 import com.google.common.base.Preconditions;
15 import com.google.common.base.Verify;
16 import java.io.Serializable;
17 import javax.annotation.Nonnull;
18 import org.opendaylight.controller.cluster.access.ABIVersion;
19 import org.opendaylight.yangtools.concepts.Immutable;
20 import org.opendaylight.yangtools.concepts.WritableIdentifier;
23 * An abstract concept of a Message. This class cannot be instantiated directly, use its specializations {@link Request}
24 * and {@link Response}.
26 * Messages have a target and a sequence number. Sequence numbers are expected to be assigned monotonically on a
27 * per-target basis, hence two targets can observe the same sequence number.
29 * This class includes explicit versioning for forward- and backward- compatibility of serialization format. This is
30 * achieved by using the serialization proxy pattern. Subclasses are in complete control of what proxy is used to
31 * serialize a particular object on the wire. This class can serve as an explicit version marker, hence no further
32 * action is necessary in the deserialization path.
34 * For the serialization path an explicit call from the user is required to select the appropriate serialization
35 * version. This is done via {@link #toVersion(ABIVersion)} method, which should return a copy of this object with
36 * the requested ABI version recorded and should return the appropriate serialization proxy.
38 * This workflow allows least disturbance across ABI versions, as all messages not affected by a ABI version bump
39 * will remain working with the same serialization format for the new ABI version.
41 * Note that this class specifies the {@link Immutable} contract, which means that all subclasses must follow this API
44 * @author Robert Varga
46 * @param <T> Target identifier type
47 * @param <C> Message type
50 public abstract class Message<T extends WritableIdentifier, C extends Message<T, C>> implements Immutable,
52 private static final long serialVersionUID = 1L;
53 private final T target;
54 private final ABIVersion version;
56 private Message(final ABIVersion version, final T target) {
57 this.target = Preconditions.checkNotNull(target);
58 this.version = Preconditions.checkNotNull(version);
61 Message(final T target) {
62 this(ABIVersion.current(), target);
65 Message(final C msg, final ABIVersion version) {
66 this(version, msg.getTarget());
70 * Get the target identifier for this message.
72 * @return Target identifier
74 public final @Nonnull T getTarget() {
79 public final ABIVersion getVersion() {
84 * Return a message which will end up being serialized in the specified {@link ABIVersion}.
86 * @param version Request {@link ABIVersion}
87 * @return A new message which will use ABIVersion as its serialization.
89 @SuppressWarnings("unchecked")
90 public final @Nonnull C toVersion(final @Nonnull ABIVersion version) {
91 if (this.version == version) {
97 return Verify.verifyNotNull(cloneAsVersion(version));
98 case TEST_PAST_VERSION:
99 case TEST_FUTURE_VERSION:
100 // Fall-through to throw
104 throw new IllegalArgumentException("Unhandled ABI version " + version);
108 * Create a copy of this message which will serialize to a stream corresponding to the specified method. This
109 * method should be implemented by the concrete final message class and should invoke the equivalent of
110 * {@link #Message(Message, ABIVersion)}.
112 * @param version target ABI version
113 * @return A message with the specified serialization stream
114 * @throws IllegalArgumentException if this message does not support the target ABI
116 protected abstract @Nonnull C cloneAsVersion(@Nonnull ABIVersion version);
119 public final String toString() {
120 return addToStringAttributes(MoreObjects.toStringHelper(this).omitNullValues()).toString();
124 * Add attributes to the output of {@link #toString()}. Subclasses wanting to contribute additional information
125 * should override this method. Any null attributes will be omitted from the output.
127 * @param toStringHelper a {@link ToStringHelper} instance
128 * @return The {@link ToStringHelper} passed in as argument
129 * @throws NullPointerException if toStringHelper is null
131 protected @Nonnull ToStringHelper addToStringAttributes(final @Nonnull ToStringHelper toStringHelper) {
132 return toStringHelper.add("target", target);
136 * Instantiate a serialization proxy for this object for the target ABI version. Implementations should return
137 * different objects for incompatible {@link ABIVersion}s. This method should never fail, as any compatibility
138 * checks should have been done by {@link #cloneAsVersion(ABIVersion)}.
140 * @param version Requested ABI version
141 * @return Proxy for this object
143 abstract @Nonnull AbstractMessageProxy<T, C> externalizableProxy(@Nonnull ABIVersion version);
145 protected final Object writeReplace() {
146 return externalizableProxy(version);