org.apache.hadoop.hive.serde2.Deserializer Maven / Gradle / Ivy
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* 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,
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* See the License for the specific language governing permissions and
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*/
package org.apache.hadoop.hive.serde2;
import java.util.Properties;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.io.Writable;
/**
* HiveDeserializer is used to deserialize the data from hadoop Writable to a
* custom java object that can be of any type that the developer wants.
*
* HiveDeserializer also provides the ObjectInspector which can be used to
* inspect the internal structure of the object (that is returned by deserialize
* function).
* All deserializers should extend the abstract class AbstractDeserializer.
* The interface is necessary for SerDes to be able to implement both Serializer and Deserializer.
*/
public interface Deserializer {
/**
* Initialize the HiveDeserializer.
*
* @param conf
* System properties
* @param tbl
* table properties
* @throws SerDeException
*/
void initialize(Configuration conf, Properties tbl) throws SerDeException;
/**
* Deserialize an object out of a Writable blob. In most cases, the return
* value of this function will be constant since the function will reuse the
* returned object. If the client wants to keep a copy of the object, the
* client needs to clone the returned deserialized value by calling
* ObjectInspectorUtils.getStandardObject().
*
* @param blob
* The Writable object containing a serialized object
* @return A Java object representing the contents in the blob.
*/
Object deserialize(Writable blob) throws SerDeException;
/**
* Get the object inspector that can be used to navigate through the internal
* structure of the Object returned from deserialize(...).
*/
ObjectInspector getObjectInspector() throws SerDeException;
/**
* Returns statistics collected when serializing
*/
SerDeStats getSerDeStats();
}