org.apache.hadoop.hive.serde2.AbstractSerDe Maven / Gradle / Ivy
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* 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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*/
package org.apache.hadoop.hive.serde2;
import java.util.Map;
import java.util.Properties;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.io.Writable;
import javax.annotation.Nullable;
/**
* Abstract class for implementing SerDe. The abstract class has been created, so that
* new methods can be added in the underlying interface, SerDe, and only implementations
* that need those methods overwrite it.
*/
public abstract class AbstractSerDe implements Deserializer, Serializer {
protected String configErrors;
/**
* Initialize the SerDe. By default, this will use one set of properties, either the
* table properties or the partition properties. If a SerDe needs access to both sets,
* it should override this method.
*
* Eventually, once all SerDes have implemented this method,
* we should convert it to an abstract method.
*
* @param configuration Hadoop configuration
* @param tableProperties Table properties
* @param partitionProperties Partition properties
* @throws SerDeException
*/
public void initialize(Configuration configuration, Properties tableProperties,
Properties partitionProperties) throws SerDeException {
initialize(configuration,
SerDeUtils.createOverlayedProperties(tableProperties, partitionProperties));
}
/**
* Initialize the HiveSerializer.
*
* @param conf
* System properties. Can be null in compile time
* @param tbl
* table properties
* @throws SerDeException
*/
@Deprecated
public abstract void initialize(@Nullable Configuration conf, Properties tbl)
throws SerDeException;
/**
* Returns the Writable class that would be returned by the serialize method.
* This is used to initialize SequenceFile header.
*/
public abstract Class getSerializedClass();
/**
* Serialize an object by navigating inside the Object with the
* ObjectInspector. In most cases, the return value of this function will be
* constant since the function will reuse the Writable object. If the client
* wants to keep a copy of the Writable, the client needs to clone the
* returned value.
*/
public abstract Writable serialize(Object obj, ObjectInspector objInspector)
throws SerDeException;
/**
* Returns statistics collected when serializing
*/
public abstract SerDeStats getSerDeStats();
/**
* 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 value by calling
* ObjectInspectorUtils.getStandardObject().
*
* @param blob
* The Writable object containing a serialized object
* @return A Java object representing the contents in the blob.
*/
public abstract 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(...).
*/
public abstract ObjectInspector getObjectInspector() throws SerDeException;
/**
* Get the error messages during the Serde configuration
*
* @return The error messages in the configuration which are empty if no error occurred
*/
public String getConfigurationErrors() {
return configErrors == null ? "" : configErrors;
}
/**
* @return Whether the SerDe that can store schema both inside and outside of metastore
* does, in fact, store it inside metastore, based on table parameters.
*/
public boolean shouldStoreFieldsInMetastore(Map tableParams) {
return false; // The default, unless SerDe overrides it.
}
}