api/src/main/java/com/datatorrent/api/Sink.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 com.datatorrent.api;

import java.lang.reflect.Array;

/**
 * Abstraction for the processing logic or consumption of a data tuple.
 * Implemented by concrete data ports for their processing behavior or by streams.
 *
 * @param <T>
 * @since 0.3.2
 */
public interface Sink<T>
{
  /**
   * Constant
   * <code>NO_SINKS</code>
   *
   * Use this constant if you need array of size 0 of sinks. Typically it's needed to confirm with
   * the code logic that expects a non null array of sinks to be passed in where you would ideally
   * pass null otherwise.
   */
  @SuppressWarnings("unchecked")
  Sink<Object>[] NO_SINKS = (Sink<Object>[])Array.newInstance(Sink.class, 0);
  /**
   * Constant
   * <code>BLACKHOLE</code>
   *
   * This sink discards anything that's put into it silently. Use this sink if you need a sink that
   * discards everything with super low cost.
   */
  Sink<Object> BLACKHOLE = new Sink<Object>()
  {
    @Override
    public void put(Object tuple)
    {
    }

    @Override
    public int getCount(boolean reset)
    {
      return 0;
    }

  };

  /**
   * Process the payload which can either be user defined object or Tuple.
   *
   * @param tuple payload to be processed by this sink.
   */
  void put(T tuple);

  /**
   * Give the count of the tuples processed since the last reset.
   *
   * @param reset reset the count if true.
   * @return the count of tuples processed since the last reset.
   */
  int getCount(boolean reset);

}