org.wikidata.wdtk.datamodel.json.jackson

Class JsonSerializer

java.lang.Object

org.wikidata.wdtk.datamodel.json.jackson.JsonSerializer

All Implemented Interfaces:

EntityDocumentDumpProcessor, EntityDocumentProcessor

public class JsonSerializer
extends Object
implements EntityDocumentDumpProcessor

This class implements EntityDocumentDumpProcessor to provide a serializer for EntityDocument objects in JSON.

The implementation does not check if open() has been called before the first document is serialized. It is the responsibility of the caller to do this.

To generate the correct official JSON serialization used by Wikidata, serialized entity documents must be based on the Jackson implementations, i.e., be instances of JacksonItemDocument or JacksonPropertyDocument. The serializer checks is this is the case and converts the data if not. If the caller can provide data based on Jackson objects or has the choice of generating data in this format (e.g., if documents are converted for filtering purposes anyway), then this will improve performance since no conversion is needed there.

Author:

Markus Kroetzsch

Field Summary

Fields

Modifier and Type	Field and Description
protected DatamodelConverter	datamodelConverter Object used to convert given entity documents to Jackson implementations for serialization whenever needed.
protected int	entityDocumentCount Counter for the number of documents serialized so far.
protected com.fasterxml.jackson.databind.ObjectMapper	mapper Object mapper that is used to serialize JSON.
protected OutputStream	outputStream The stream that the resulting JSON is written to.

Constructor Summary

Constructors

Constructor and Description
JsonSerializer(OutputStream outputStream) Creates a new JSON serializer that writes its output to the given stream.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Finishes the processing by performing any final steps, such as closing resources.
int	getEntityDocumentCount() Returns the number of entity documents serialized so far.
void	open() Starts the processing by performing any initial steps to prepare processing.
void	processItemDocument(ItemDocument itemDocument) Processes the given ItemDocument.
void	processPropertyDocument(PropertyDocument propertyDocument) Processes the given PropertyDocument.
protected void	reportException(Exception e) Reports a given exception as a RuntimeException, since the interface does not allow us to throw checked exceptions directly.
protected void	serializeEntityDocument(EntityDocument entityDocument) Writes the JSON serialization of the given EntityDocument.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

outputStream

protected final OutputStream outputStream

The stream that the resulting JSON is written to.

datamodelConverter

protected final DatamodelConverter datamodelConverter

Object used to convert given entity documents to Jackson implementations for serialization whenever needed.

mapper

protected final com.fasterxml.jackson.databind.ObjectMapper mapper

Object mapper that is used to serialize JSON.

entityDocumentCount

protected int entityDocumentCount

Counter for the number of documents serialized so far.

Constructor Detail

JsonSerializer

public JsonSerializer(OutputStream outputStream)

Creates a new JSON serializer that writes its output to the given stream. The output stream will be managed by the object, i.e., it will be closed when close() is call ed.

Parameters:

outputStream - the output stream to write to

Method Detail

open

public void open()

Description copied from interface: EntityDocumentDumpProcessor

Starts the processing by performing any initial steps to prepare processing.

Specified by:

open in interface EntityDocumentDumpProcessor

processItemDocument

public void processItemDocument(ItemDocument itemDocument)

Description copied from interface: EntityDocumentProcessor

Processes the given ItemDocument.

Specified by:

processItemDocument in interface EntityDocumentProcessor

Parameters:

itemDocument - the ItemDocument

processPropertyDocument

public void processPropertyDocument(PropertyDocument propertyDocument)

Description copied from interface: EntityDocumentProcessor

Processes the given PropertyDocument.

Specified by:

processPropertyDocument in interface EntityDocumentProcessor

Parameters:

propertyDocument - the PropertyDocument

close

public void close()

Description copied from interface: EntityDocumentDumpProcessor

Finishes the processing by performing any final steps, such as closing resources.

Specified by:

close in interface EntityDocumentDumpProcessor

getEntityDocumentCount

public int getEntityDocumentCount()

Returns the number of entity documents serialized so far.

Returns:

number of serialized entity documents

reportException

protected void reportException(Exception e)

Reports a given exception as a RuntimeException, since the interface does not allow us to throw checked exceptions directly.

Parameters:

e - the exception to report

Throws:

RuntimeException - in all cases

serializeEntityDocument

protected void serializeEntityDocument(EntityDocument entityDocument)

Writes the JSON serialization of the given EntityDocument.

Parameters:

entityDocument - the document to serialize