kafka DelegatingPeekingKeyValueIterator 源码
kafka DelegatingPeekingKeyValueIterator 代码
文件路径：/streams/src/main/java/org/apache/kafka/streams/state/internals/DelegatingPeekingKeyValueIterator.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.state.internals;
import org.apache.kafka.streams.KeyValue;
import org.apache.kafka.streams.errors.InvalidStateStoreException;
import org.apache.kafka.streams.state.KeyValueIterator;
import java.util.NoSuchElementException;
/**
* Optimized {@link KeyValueIterator} used when the same element could be peeked multiple times.
*/
public class DelegatingPeekingKeyValueIterator<K, V> implements KeyValueIterator<K, V>, PeekingKeyValueIterator<K, V> {
private final KeyValueIterator<K, V> underlying;
private final String storeName;
private KeyValue<K, V> next;
private volatile boolean open = true;
public DelegatingPeekingKeyValueIterator(final String storeName, final KeyValueIterator<K, V> underlying) {
this.storeName = storeName;
this.underlying = underlying;
}
@Override
public synchronized K peekNextKey() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return next.key;
}
@Override
public synchronized void close() {
underlying.close();
open = false;
}
@Override
public synchronized boolean hasNext() {
if (!open) {
throw new InvalidStateStoreException(String.format("Store %s has closed", storeName));
}
if (next != null) {
return true;
}
if (!underlying.hasNext()) {
return false;
}
next = underlying.next();
return true;
}
@Override
public synchronized KeyValue<K, V> next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
final KeyValue<K, V> result = next;
next = null;
return result;
}
@Override
public KeyValue<K, V> peekNext() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return next;
}
}
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