org.apache.kafka.streams.query.VersionedKeyQuery Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.kafka.streams.query;
import org.apache.kafka.common.annotation.InterfaceStability.Evolving;
import org.apache.kafka.streams.state.VersionedRecord;
import java.time.Instant;
import java.util.Objects;
import java.util.Optional;
/**
* Interactive query for retrieving a single record from a versioned state store based on its key and timestamp.
*
* @param The type of the key.
* @param The type of the value.
*/
@Evolving
public final class VersionedKeyQuery implements Query> {
private final K key;
private final Optional asOfTimestamp;
private VersionedKeyQuery(final K key, final Optional asOfTimestamp) {
this.key = key;
this.asOfTimestamp = asOfTimestamp;
}
/**
* Creates a query that will retrieve the record from a versioned state store identified by {@code key} if it exists
* (or {@code null} otherwise).
*
* While the query by default returns the latest value of the specified {@code key}, setting
* the {@code asOfTimestamp} (by calling the {@link #asOf(Instant)} method), makes the query
* to return the value associated to the specified {@code asOfTimestamp}.
*
* @param key The key to retrieve
* @param The type of the key
* @param The type of the value that will be retrieved
* @throws NullPointerException if {@code key} is null
*/
public static VersionedKeyQuery withKey(final K key) {
Objects.requireNonNull(key, "key cannot be null.");
return new VersionedKeyQuery<>(key, Optional.empty());
}
/**
* Specifies the timestamp for the key query. The key query returns the record's version for the specified timestamp.
* (To be more precise: The key query returns the record with the greatest timestamp <= asOfTimestamp)
*
* @param asOfTimestamp The timestamp of the query.
* @throws NullPointerException if {@code asOfTimestamp} is null
*/
public VersionedKeyQuery asOf(final Instant asOfTimestamp) {
Objects.requireNonNull(asOfTimestamp, "asOf timestamp cannot be null.");
return new VersionedKeyQuery<>(key, Optional.of(asOfTimestamp));
}
/**
* The key that was specified for this query.
* @return The specified {@code key} of the query.
*/
public K key() {
return key;
}
/**
* The timestamp of the query, if specified.
* @return The specified {@code asOfTimestamp} of the query.
*/
public Optional asOfTimestamp() {
return asOfTimestamp;
}
}