storm-client/src/jvm/org/apache/storm/streams/processors/AggregateProcessor.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.storm.streams.processors;

import org.apache.storm.streams.operations.CombinerAggregator;

public class AggregateProcessor<T, A, R> extends BaseProcessor<T> implements BatchProcessor {
    private final CombinerAggregator<T, A, R> aggregator;
    private final boolean emitAggregate;
    private A state;

    public AggregateProcessor(CombinerAggregator<T, A, R> aggregator) {
        this(aggregator, false);
    }

    public AggregateProcessor(CombinerAggregator<T, A, R> aggregator, boolean emitAggregate) {
        this.aggregator = aggregator;
        this.emitAggregate = emitAggregate;
    }

    @Override
    public void execute(T input) {
        if (state == null) {
            state = aggregator.init();
        }
        state = aggregator.apply(state, input);
        if (emitAggregate) {
            mayBeForwardAggUpdate(() -> state);
        } else {
            mayBeForwardAggUpdate(() -> aggregator.result(state));
        }
    }

    @Override
    public void finish() {
        if (state != null) {
            if (emitAggregate) {
                context.forward(state);
            } else {
                context.forward(aggregator.result(state));
            }
            state = null;
        }
    }

    @Override
    public String toString() {
        return "AggregateProcessor{"
                + "aggregator=" + aggregator
                + ", emitAggregate=" + emitAggregate
                + ", state=" + state
                + "}";
    }
}