samza-api/src/main/java/org/apache/samza/startpoint/Startpoint.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.samza.startpoint;

import com.google.common.base.MoreObjects;
import com.google.common.base.Objects;
import java.time.Instant;
import org.apache.samza.annotation.InterfaceStability;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

/**
 * Startpoint represents a position in a stream partition.
 */
@InterfaceStability.Evolving
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "@type")
public abstract class Startpoint {
  // TODO: Remove the @JsonTypeInfo annotation and use the ObjectMapper#enableDefaultTyping method in
  //  StartpointObjectMapper after upgrading jackson version. That method does not add the appropriate type info to the
  //  serialized json with the current version (1.9.13) of jackson.

  private final long creationTimestamp;

  Startpoint() {
    this(Instant.now().toEpochMilli());
  }

  Startpoint(long creationTimestamp) {
    this.creationTimestamp = creationTimestamp;
  }

  /**
   * The timestamp when this {@link Startpoint} was written to the storage layer.
   * @return a timestamp in epoch milliseconds.
   */
  public long getCreationTimestamp() {
    return creationTimestamp;
  }

  /**
   * Applies the {@link StartpointVisitor}'s visit methods to the {@link Startpoint}
   * and returns the result of that operation.
   * @param input the metadata associated with the startpoint.
   * @param startpointVisitor the visitor of the startpoint.
   * @return the result of applying the visitor on startpoint.
   */
  public abstract <IN, OUT> OUT apply(IN input, StartpointVisitor<IN, OUT> startpointVisitor);

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this).toString();
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    Startpoint that = (Startpoint) o;
    return Objects.equal(creationTimestamp, that.creationTimestamp);
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(creationTimestamp);
  }
}