de.gerdiproject.harvest.etls.extractors

Interface IExtractor<T>

Type Parameters:

T - the type of objects that are extracted

All Known Implementing Classes:

AbstractIteratorExtractor, JsonArrayExtractor

public interface IExtractor<T>

This class represents the Extractor of an ETL process.

Author:

Robin Weiss

Method Summary

Modifier and Type	Method and Description
void	clear() Closes potentially open readers/writers and finishes the Extraction process if it is still ongoing.
T	extract() Extracts elements from a source repository.
String	getUniqueVersionString() Returns a string that can be hashed to generate a unique identifier for the current version of the extractable elements.
void	init(AbstractETL<?,?> etl) Initializes the extractor for a new harvest.
int	size() Returns the number of extractable documents, or -1 if they cannot be estimated.

Method Detail

init

void init(AbstractETL<?,?> etl)

Initializes the extractor for a new harvest.

Parameters:

etl - the AbstractETL to which the extractor belongs

extract

T extract()
   throws ExtractorException

Extracts elements from a source repository.

Returns:

an object that is to be transformed

Throws:

ExtractorException - thrown when the extraction fails

getUniqueVersionString

String getUniqueVersionString()

Returns a string that can be hashed to generate a unique identifier for the current version of the extractable elements.

Returns:

a unique version of the extractable elements

size

int size()

Returns the number of extractable documents, or -1 if they cannot be estimated.

Returns:

the number of extractable documents, or -1

clear

void clear()

Closes potentially open readers/writers and finishes the Extraction process if it is still ongoing.