library/src/main/java/org/apache/apex/malhar/lib/util/UnifierArrayList.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.apex.malhar.lib.util;

import java.util.ArrayList;

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Operator.Unifier;

/**
 * This unifier takes lists as input tuples. 
 * The unifier combines all the lists it receives within an application window and emits them at the end of the window.
 * <p>
 * The processing is done with sticky key partitioning, i.e. each one key belongs only to one partition.
 * </p>
 * @displayName Unifier Array List
 * @category Algorithmic
 * @tags unifier
 * @since 0.3.3
 */
public class UnifierArrayList<K> implements Unifier<ArrayList<K>>
{
  // merged list
  private ArrayList<K> mergedList;

  @Override
  public void beginWindow(long arg0)
  {
    mergedList = new ArrayList<K>();
  }

  @Override
  public void endWindow()
  {
    mergedport.emit(mergedList);
  }

  @Override
  public void setup(OperatorContext arg0)
  {
    // TODO Auto-generated method stub

  }

  @Override
  public void teardown()
  {
    // TODO Auto-generated method stub

  }

  /**
   * This is the output port that emits a merged list constructed from input lists.
   */
  public final transient DefaultOutputPort<ArrayList<K>> mergedport = new DefaultOutputPort<ArrayList<K>>();

  @Override
  public void process(ArrayList<K> tuple)
  {
    for (int i = 0; i < tuple.size(); i++) {
      mergedList.add(tuple.get(i));
    }
  }

}