| /* |
| * Copyright 2015 Open Networking Laboratory |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.onosproject.store.service; |
| |
| import java.util.function.Function; |
| |
| import org.joda.time.DateTime; |
| import org.onlab.util.ByteArraySizeHashPrinter; |
| |
| import com.google.common.base.MoreObjects; |
| import com.google.common.base.Objects; |
| |
| /** |
| * Versioned value. |
| * |
| * @param <V> value type. |
| */ |
| public class Versioned<V> { |
| |
| private final V value; |
| private final long version; |
| private final long creationTime; |
| |
| /** |
| * Constructs a new versioned value. |
| * @param value value |
| * @param version version |
| * @param creationTime milliseconds of the creation event |
| * from the Java epoch of 1970-01-01T00:00:00Z |
| */ |
| public Versioned(V value, long version, long creationTime) { |
| this.value = value; |
| this.version = version; |
| this.creationTime = creationTime; |
| } |
| |
| /** |
| * Constructs a new versioned value. |
| * @param value value |
| * @param version version |
| */ |
| public Versioned(V value, long version) { |
| this(value, version, System.currentTimeMillis()); |
| } |
| |
| /** |
| * Returns the value. |
| * |
| * @return value. |
| */ |
| public V value() { |
| return value; |
| } |
| |
| /** |
| * Returns the version. |
| * |
| * @return version |
| */ |
| public long version() { |
| return version; |
| } |
| |
| /** |
| * Returns the system time when this version was created. |
| * <p> |
| * Care should be taken when relying on creationTime to |
| * implement any behavior in a distributed setting. Due |
| * to the possibility of clock skew it is likely that |
| * even creationTimes of causally related versions can be |
| * out or order. |
| * @return creation time |
| */ |
| public long creationTime() { |
| return creationTime; |
| } |
| |
| /** |
| * Maps this instance into another after transforming its |
| * value while retaining the same version and creationTime. |
| * @param transformer function for mapping the value |
| * @param <U> value type of the returned instance |
| * @return mapped instance |
| */ |
| public <U> Versioned<U> map(Function<V, U> transformer) { |
| return new Versioned<>(transformer.apply(value), version, creationTime); |
| } |
| |
| /** |
| * Returns the value of the specified Versioned object if non-null or else returns |
| * a default value. |
| * @param versioned versioned object |
| * @param defaultValue default value to return if versioned object is null |
| * @param <U> type of the versioned value |
| * @return versioned value or default value if versioned object is null |
| */ |
| public static <U> U valueOrElse(Versioned<U> versioned, U defaultValue) { |
| return versioned == null ? defaultValue : versioned.value(); |
| } |
| |
| /** |
| * Returns the value of the specified Versioned object if non-null or else returns null. |
| * @param versioned versioned object |
| * @param <U> type of the versioned value |
| * @return versioned value or null if versioned object is null |
| */ |
| public static <U> U valueOrNull(Versioned<U> versioned) { |
| return valueOrElse(versioned, null); |
| } |
| |
| @Override |
| public int hashCode() { |
| return Objects.hashCode(value, version, creationTime); |
| } |
| |
| @Override |
| public boolean equals(Object other) { |
| if (!(other instanceof Versioned)) { |
| return false; |
| } |
| Versioned<V> that = (Versioned) other; |
| return Objects.equal(this.value, that.value) && |
| Objects.equal(this.version, that.version) && |
| Objects.equal(this.creationTime, that.creationTime); |
| } |
| |
| @Override |
| public String toString() { |
| return MoreObjects.toStringHelper(this) |
| .add("value", value instanceof byte[] ? new ByteArraySizeHashPrinter((byte[]) value) : value) |
| .add("version", version) |
| .add("creationTime", new DateTime(creationTime)) |
| .toString(); |
| } |
| } |