org.apache.flink.runtime.state.KeyExtractorFunction 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.flink.runtime.state;
import javax.annotation.Nonnull;
/**
* Function to extract a key from a given object.
*
* @param type of the element from which we extract the key.
*/
@FunctionalInterface
public interface KeyExtractorFunction {
KeyExtractorFunction> FOR_KEYED_OBJECTS = new KeyExtractorFunction>() {
@Nonnull
@Override
public Object extractKeyFromElement(@Nonnull Keyed element) {
return element.getKey();
}
};
/**
* Returns the key for the given element by which the key-group can be computed.
*/
@Nonnull
Object extractKeyFromElement(@Nonnull T element);
@SuppressWarnings("unchecked")
static > KeyExtractorFunction forKeyedObjects() {
return (KeyExtractorFunction) FOR_KEYED_OBJECTS;
}
}