PairElementWithPropertyValue.java

/*
 * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
 *
 * Licensed 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.gradoop.flink.model.impl.functions.epgm;

import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.api.java.functions.FunctionAnnotation;
import org.apache.flink.api.java.tuple.Tuple2;
import org.gradoop.common.model.api.entities.Element;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.common.model.impl.properties.PropertyValue;

/**
 * {@code element -> (elementId, propertyValue)}
 *
 * @param <EL> element type
 */
@FunctionAnnotation.ForwardedFields("id->f0")
public class PairElementWithPropertyValue<EL extends Element>
  implements MapFunction<EL, Tuple2<GradoopId, PropertyValue>> {

  /**
   * Used to access property value to return.
   */
  private final String propertyKey;

  /**
   * Reduce instantiations.
   */
  private final Tuple2<GradoopId, PropertyValue> reuseTuple;

  /**
   * Constructor.
   *
   * @param propertyKey used to access property value
   */
  public PairElementWithPropertyValue(String propertyKey) {
    this.propertyKey  = propertyKey;
    this.reuseTuple   = new Tuple2<>();
  }

  @Override
  public Tuple2<GradoopId, PropertyValue> map(EL el) throws Exception {
    reuseTuple.f0 = el.getId();
    if (el.hasProperty(propertyKey)) {
      reuseTuple.f1 = el.getPropertyValue(propertyKey);
    } else {
      reuseTuple.f1 = PropertyValue.NULL_VALUE;
    }
    return reuseTuple;
  }
}