samoa-api/src/main/java/org/apache/samoa/core/EntranceProcessor.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.samoa.core;

import java.io.Serializable;

import com.github.javacliparser.Configurable;

/**
 * An EntranceProcessor is a specific kind of processor dedicated to providing events to inject in the topology. It can
 * be connected to a single output stream.
 */
public interface EntranceProcessor extends Serializable, Configurable, Processor {

  /**
   * Initializes the Processor. This method is called once after the topology is set up and before any call to the
   * {@link nextTuple} method.
   * 
   * @param the
   *          identifier of the processor.
   */
  public void onCreate(int id);

  /**
   * Checks whether the source stream is finished/exhausted.
   */
  public boolean isFinished();

  /**
   * Checks whether a new event is ready to be processed.
   * 
   * @return true if the EntranceProcessor is ready to provide the next event, false otherwise.
   */
  public boolean hasNext();

  /**
   * Provides the next tuple to be processed by the topology. This method is the entry point for external events into
   * the topology.
   * 
   * @return the next event to be processed.
   */
  public ContentEvent nextEvent();

}