com.datatorrent.api.StreamCodec Maven / Gradle / Ivy
/**
* 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 com.datatorrent.netlet.util.Slice;
/**
* Serializing and Deserializing the data tuples and controlling the partitioning
*
* Data flows from one Operator to another Operator through a stream.Typically
* StreamCodec is defined on each input stream and is able to
* serialize/deserialize and partition the data of type supported by the stream.
*
*
* For a few known types, the system is able to determine the StreamCodec. In
* all other cases, it would need user to define the codec on each input stream.
*
*
* In the physical layout, each codec has at least 2 instances - serializer
* instance which attaches itself to the stream coming out of upstream operator
* and deserializer instance which attaches itself to input stream of downstream
* operator.
*
* @param data type of the tuples on the stream
* @since 0.3.2
*/
public interface StreamCodec
{
/**
* Create POJO from the byte array for consumption by the downstream.
*
* @param fragment
* @return plain old java object, the type is intentionally not T since the consumer does not care about it.
*/
Object fromByteArray(Slice fragment);
/**
* Serialize the POJO emitted by the upstream node to byte array so that
* it can be transmitted or stored in file
*
* @param o plain old java object
* @return serialized representation of the object
*/
Slice toByteArray(T o);
/**
* Get the partition on the object to be delivered to the downstream
* so that it can be sent to appropriate downstream node if the load
* balancing per partition is in effect.
*
* @param o object for which the partition has to be determined
* @return partition for the object
*/
int getPartition(T o);
}