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StreamletOperator.java
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StreamletOperator.java
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/**
* 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.heron.streamlet.impl.operators;
import java.util.Map;
import org.apache.heron.api.bolt.BaseRichBolt;
import org.apache.heron.api.bolt.OutputCollector;
import org.apache.heron.api.topology.OutputFieldsDeclarer;
import org.apache.heron.api.topology.TopologyContext;
import org.apache.heron.api.tuple.Fields;
import org.apache.heron.streamlet.IStreamletRichOperator;
/**
* The Bolt interface that other operators of the streamlet packages extend.
* The only common stuff amongst all of them is the output streams
*/
public abstract class StreamletOperator<R, T>
extends BaseRichBolt
implements IStreamletRichOperator<R, T> {
private static final long serialVersionUID = 8524238140745238942L;
private static final String OUTPUT_FIELD_NAME = "output";
protected OutputCollector collector;
@SuppressWarnings("rawtypes")
@Override
public void prepare(Map<String, Object> map,
TopologyContext topologyContext,
OutputCollector outputCollector) {
collector = outputCollector;
}
/**
* The operators implementing streamlet functionality have some properties.
* 1. They all output only one stream
* 2. They should be able to consume each other's output
* This imply that the output stream should be named same for all of them.
*/
@Override
public void declareOutputFields(OutputFieldsDeclarer outputFieldsDeclarer) {
outputFieldsDeclarer.declare(new Fields(OUTPUT_FIELD_NAME));
}
}