kafka ValueMapper 源码
kafka ValueMapper 代码
文件路径：/streams/src/main/java/org/apache/kafka/streams/kstream/ValueMapper.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.kstream;
/**
* The {@code ValueMapper} interface for mapping a value to a new value of arbitrary type.
* This is a stateless record-by-record operation, i.e, {@link #apply(Object)} is invoked individually for each record
* of a stream (cf. {@link ValueTransformer} for stateful value transformation).
* If {@code ValueMapper} is applied to a {@link org.apache.kafka.streams.KeyValue key-value pair} record the record's
* key is preserved.
* If a record's key and value should be modified {@link KeyValueMapper} can be used.
*
* @param <V> value type
* @param <VR> mapped value type
* @see KeyValueMapper
* @see ValueTransformer
* @see ValueTransformerWithKey
* @see KStream#mapValues(ValueMapper)
* @see KStream#mapValues(ValueMapperWithKey)
* @see KStream#flatMapValues(ValueMapper)
* @see KStream#flatMapValues(ValueMapperWithKey)
* @see KTable#mapValues(ValueMapper)
* @see KTable#mapValues(ValueMapperWithKey)
*/
public interface ValueMapper<V, VR> {
/**
* Map the given value to a new value.
*
* @param value the value to be mapped
* @return the new value
*/
VR apply(final V value);
}
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