| /** |
| * 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.storm.streams.operations; |
| |
| /** |
| * Interface for updating state. |
| * |
| * @param <T> the value type |
| * @param <S> the state type |
| */ |
| public interface StateUpdater<T, S> extends Operation { |
| /** |
| * A static factory to create a {@link StateUpdater} based on an initial value of the state and a state update function. |
| * |
| * @param initialValue the intial value of the state |
| * @param stateUpdateFn the state update function |
| * @param <T> the value type |
| * @param <S> the state type |
| * @return the {@link StateUpdater} |
| */ |
| static <T, S> StateUpdater<T, S> of(S initialValue, |
| BiFunction<? super S, ? super T, ? extends S> stateUpdateFn) { |
| return new StateUpdater<T, S>() { |
| @Override |
| public S init() { |
| return initialValue; |
| } |
| |
| @Override |
| public S apply(S state, T value) { |
| return stateUpdateFn.apply(state, value); |
| } |
| }; |
| } |
| |
| /** |
| * The initial value of the state to start with. |
| * |
| * @return the initial value of the state |
| */ |
| S init(); |
| |
| /** |
| * Returns a new state by applying the value on the current state. |
| * |
| * @param state the current state |
| * @param value the value |
| * @return the new state |
| */ |
| S apply(S state, T value); |
| } |