kafka KeyQuery 源码
kafka KeyQuery 代码
文件路径：/streams/src/main/java/org/apache/kafka/streams/query/KeyQuery.java
/*
* 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 java.util.Objects;
/**
* Interactive query for retrieving a single record based on its key.
*/
@Evolving
public final class KeyQuery<K, V> implements Query<V> {
private final K key;
private final boolean skipCache;
private KeyQuery(final K key, final boolean skipCache) {
this.key = Objects.requireNonNull(key);
this.skipCache = skipCache;
}
/**
* Creates a query that will retrieve the record identified by {@code key} if it exists
* (or {@code null} otherwise).
* @param key The key to retrieve
* @param <K> The type of the key
* @param <V> The type of the value that will be retrieved
*/
public static <K, V> KeyQuery<K, V> withKey(final K key) {
return new KeyQuery<>(key, false);
}
/**
* Specifies that the cache should be skipped during query evaluation. This means, that the query will always
* get forwarded to the underlying store.
*/
public KeyQuery<K, V> skipCache() {
return new KeyQuery<>(key, true);
}
/**
* The key that was specified for this query.
*/
public K getKey() {
return key;
}
/**
* The flag whether to skip the cache or not during query evaluation.
*/
public boolean isSkipCache() {
return skipCache;
}
}
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