eu.slipo.athenarc.triplegeo.tools

Class JsonToRdf

java.lang.Object

eu.slipo.athenarc.triplegeo.tools.JsonToRdf

public class JsonToRdf
extends java.lang.Object

Main entry point of the utility for extracting RDF triples from JSON documents. LIMITATIONS: The entire JSON document is read in memory before parsing, so large files require suitable configuration of the JVM heap size.

Version:

2.0

Author:

Kostas Patroumpas

Field Summary

Fields

Modifier and Type	Field and Description
private Classification	classification
private static org.opengis.referencing.crs.CRSAuthorityFactory	crsFactory
private Configuration	currentConfig
private java.lang.String	inputFile
(package private) Assistant	myAssistant
(package private) Converter	myConverter
private java.lang.String	outputFile
private org.opengis.referencing.operation.MathTransform	reproject
(package private) int	sourceSRID
(package private) int	targetSRID

Constructor Summary

Constructors

Constructor and Description
JsonToRdf(Configuration config, Classification classific, java.lang.String inFile, java.lang.String outFile, int sourceSRID, int targetSRID) Constructor for the transformation process from JSON document to RDF.

Method Summary

Modifier and Type	Method and Description
void	apply() Applies transformation according to the configuration settings.
private void	flattener(java.util.Map<java.lang.String,java.lang.String> record, java.util.Map.Entry<java.lang.String,com.fasterxml.jackson.databind.JsonNode> node, java.util.List<java.lang.String> names) Flattens any nested properties in the given JSON node.
private void	parseArrayNode(com.fasterxml.jackson.databind.node.ArrayNode arrayNode) Parses an array of object nodes, by invoking processing for each of them.
private void	parseDocument(byte[] json) Parse each item in the input JSON document in order to create the necessary triples (including geometric and non-spatial attributes).
private void	parseNestedArray(java.util.Map<java.lang.String,java.lang.String> record, java.lang.String key, com.fasterxml.jackson.databind.node.ArrayNode arrayNode) Handles a nested array of properties under an identified object (feature), by essentially parsing each of them.
private void	parseNestedArrayNode(java.util.Map<java.lang.String,java.lang.String> record, java.lang.String key, int k, com.fasterxml.jackson.databind.JsonNode jsonNode) Parses and possibly flattens a JSON properties node (i.e., properties listed as distinct items in an array).
private java.util.Map<java.lang.String,java.lang.String>	parseObjectNode(com.fasterxml.jackson.databind.JsonNode jsonNode) Parses and possibly flattens a JSON object node.
private void	processRecord(java.util.Map<java.lang.String,java.lang.String> record) Submit a single feature (with a geometry and all its non-spatial properties) for transformation.

Methods inherited from class java.lang.Object

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

Field Detail

myConverter

Converter myConverter

myAssistant

Assistant myAssistant

reproject

private org.opengis.referencing.operation.MathTransform reproject

sourceSRID

int sourceSRID

targetSRID

int targetSRID

currentConfig

private Configuration currentConfig

classification

private Classification classification

inputFile

private java.lang.String inputFile

outputFile

private java.lang.String outputFile

crsFactory

private static final org.opengis.referencing.crs.CRSAuthorityFactory crsFactory

Constructor Detail

JsonToRdf

public JsonToRdf(Configuration config,
                 Classification classific,
                 java.lang.String inFile,
                 java.lang.String outFile,
                 int sourceSRID,
                 int targetSRID)
          throws java.lang.ClassNotFoundException

Constructor for the transformation process from JSON document to RDF.

Parameters:

config - Parameters to configure the transformation.

classific - Instantiation of the classification scheme that assigns categories to input features.

inFile - Path to input JSON file.

outFile - Path to the output file that collects RDF triples.

sourceSRID - Spatial reference system (EPSG code) of the input JSON file.

targetSRID - Spatial reference system (EPSG code) of geometries in the output RDF triples.

Throws:

java.lang.ClassNotFoundException

Method Detail

apply

public void apply()

Applies transformation according to the configuration settings.

parseObjectNode

private java.util.Map<java.lang.String,java.lang.String> parseObjectNode(com.fasterxml.jackson.databind.JsonNode jsonNode)

Parses and possibly flattens a JSON object node.

Parameters:

jsonNode - The JSON node to be parsed.

Returns:

A map with (flattened) properties as keys and their respective values as identified in the given JSON node.

parseNestedArrayNode

private void parseNestedArrayNode(java.util.Map<java.lang.String,java.lang.String> record,
                                  java.lang.String key,
                                  int k,
                                  com.fasterxml.jackson.databind.JsonNode jsonNode)

Parses and possibly flattens a JSON properties node (i.e., properties listed as distinct items in an array).

Parameters:

record - A map updated with (flattened) properties as keys and their respective values as identified in the given JSON node.

key - The name of the parent property.

k - The serial number of the item in the underlying array.

jsonNode - The JSON node to be parsed.

parseNestedArray

private void parseNestedArray(java.util.Map<java.lang.String,java.lang.String> record,
                              java.lang.String key,
                              com.fasterxml.jackson.databind.node.ArrayNode arrayNode)

Handles a nested array of properties under an identified object (feature), by essentially parsing each of them.

Parameters:

key - The name of the parent property.

arrayNode - A JSON node representing an array of children nodes.

parseArrayNode

private void parseArrayNode(com.fasterxml.jackson.databind.node.ArrayNode arrayNode)

Parses an array of object nodes, by invoking processing for each of them.

Parameters:

arrayNode - The parent node representing an array of object nodes.

flattener

private void flattener(java.util.Map<java.lang.String,java.lang.String> record,
                       java.util.Map.Entry<java.lang.String,com.fasterxml.jackson.databind.JsonNode> node,
                       java.util.List<java.lang.String> names)

Flattens any nested properties in the given JSON node.

Parameters:

record - Map structure to collect the flattened properties (keys) and their values.

node - JSON node to be flattened.

names - Prefix names for the keys to be generated.

processRecord

private void processRecord(java.util.Map<java.lang.String,java.lang.String> record)

Submit a single feature (with a geometry and all its non-spatial properties) for transformation.

Parameters:

record - Map structure that has collected all flattened properties (as keys) and their respective values.

parseDocument

private void parseDocument(byte[] json)

Parse each item in the input JSON document in order to create the necessary triples (including geometric and non-spatial attributes).

Parameters:

json - The JSON document having (maybe nested) properties per item.